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• ADF Business Components

  - by Arda Eralp

  ADF Business Components and JDeveloper simplify the development, delivery, and customization of business applications for the Java EE platform. With ADF Business Components, developers aren't required to write the application infrastructure code required by the typical Java EE application to: Connect to the database Retrieve data Lock database records Manage transactions   ADF Business Components addresses these tasks through its library of reusable software components and through the supporting design time facilities in JDeveloper. Most importantly, developers save time using ADF Business Components since the JDeveloper design time makes typical development tasks entirely declarative. In particular, JDeveloper supports declarative development with ADF Business Components to: Author and test business logic in components which automatically integrate with databases Reuse business logic through multiple SQL-based views of data, supporting different application tasks Access and update the views from browser, desktop, mobile, and web service clients Customize application functionality in layers without requiring modification of the delivered application The goal of ADF Business Components is to make the business services developer more productive.   ADF Business Components provides a foundation of Java classes that allow your business-tier application components to leverage the functionality provided in the following areas: Simplifying Data Access Design a data model for client displays, including only necessary data Include master-detail hierarchies of any complexity as part of the data model Implement end-user Query-by-Example data filtering without code Automatically coordinate data model changes with business services layer Automatically validate and save any changes to the database   Enforcing Business Domain Validation and Business Logic Declaratively enforce required fields, primary key uniqueness, data precision-scale, and foreign key references Easily capture and enforce both simple and complex business rules, programmatically or declaratively, with multilevel validation support Navigate relationships between business domain objects and enforce constraints related to compound components   Supporting Sophisticated UIs with Multipage Units of Work Automatically reflect changes made by business service application logic in the user interface Retrieve reference information from related tables, and automatically maintain the information when the user changes foreign-key values Simplify multistep web-based business transactions with automatic web-tier state management Handle images, video, sound, and documents without having to use code Synchronize pending data changes across multiple views of data Consistently apply prompts, tooltips, format masks, and error messages in any application Define custom metadata for any business components to support metadata-driven user interface or application functionality Add dynamic attributes at runtime to simplify per-row state management   Implementing High-Performance Service-Oriented Architecture Support highly functional web service interfaces for business integration without writing code Enforce best-practice interface-based programming style Simplify application security with automatic JAAS integration and audit maintenance "Write once, run anywhere": use the same business service as plain Java class, EJB session bean, or web service   Streamlining Application Customization Extend component functionality after delivery without modifying source code Globally substitute delivered components with extended ones without modifying the application   ADF Business Components implements the business service through the following set of cooperating components: Entity object An entity object represents a row in a database table and simplifies modifying its data by handling all data manipulation language (DML) operations for you. These are basically your 1 to 1 representation of a database table. Each table in the database will have 1 and only 1 EO. The EO contains the mapping between columns and attributes. EO's also contain the business logic and validation. These are you core data services. They are responsible for updating, inserting and deleting records. The Attributes tab displays the actual mapping between attributes and columns, the mapping has following fields: Name : contains the name of the attribute we expose in our data model. Type : defines the data type of the attribute in our application. Column : specifies the column to which we want to map the attribute with Column Type : contains the type of the column in the database   View object A view object represents a SQL query. You use the full power of the familiar SQL language to join, filter, sort, and aggregate data into exactly the shape required by the end-user task. The attributes in the View Objects are actually coming from the Entity Object. In the end the VO will generate a query but you basically build a VO by selecting which EO need to participate in the VO and which attributes of those EO you want to use. That's why you have the Entity Usage column so you can see the relation between VO and EO. In the query tab you can clearly see the query that will be generated for the VO. At this stage we don't need it and just use it for information purpose. In later stages we might use it. Application module An application module is the controller of your data layer. It is responsible for keeping hold of the transaction. It exposes the data model to the view layer. You expose the VO's through the Application Module. This is the abstraction of your data layer which you want to show to the outside word.It defines an updatable data model and top-level procedures and functions (called service methods) related to a logical unit of work related to an end-user task. While the base components handle all the common cases through built-in behavior, customization is always possible and the default behavior provided by the base components can be easily overridden or augmented. When you create EO's, a foreign key will be translated into an association in our model. It defines the type of relation and who is the master and child as well as how the visibility of the association looks like. A similar concept exists to identify relations between view objects. These are called view links. These are almost identical as association except that a view link is based upon attributes defined in the view object. It can also be based upon an association. Here's a short summary: Entity Objects: representations of tables Association: Relations between EO's. Representations of foreign keys View Objects: Logical model View Links: Relationships between view objects Application Model: interface to your application  

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• ADF Reusable Artefacts

  - by Arda Eralp

  Primary reusable ADF Business Component: Entity Objects (EOs) View Objects (VOs) Application Modules (AMs) Framework Extensions Classes Primary reusable ADF Controller: Bounded Task Flows (BTFs) Task Flow Templates Primary reusable ADF Faces: Page Templates Skins Declarative Components Utility Classes Certain components will often be used more than once. Whether the reuse happens within the same application, or across different applications, it is often advantageous to package these reusable components into a library that can be shared between different developers, across different teams, and even across departments within an organization. In the world of Java object-oriented programming, reusing classes and objects is just standard procedure. With the introduction of the model-view-controller (MVC) architecture, applications can be further modularized into separate model, view, and controller layers. By separating the data (model and business services layers) from the presentation (view and controller layers), you ensure that changes to any one layer do not affect the integrity of the other layers. You can change business logic without having to change the UI, or redesign the web pages or front end without having to recode domain logic. Oracle ADF and JDeveloper support the MVC design pattern. When you create an application in JDeveloper, you can choose many application templates that automatically set up data model and user interface projects. Because the different MVC layers are decoupled from each other, development can proceed on different projects in parallel and with a certain amount of independence. ADF Library further extends this modularity of design by providing a convenient and practical way to create, deploy, and reuse high-level components. When you first design your application, you design it with component reusability in mind. If you created components that can be reused, you can package them into JAR files and add them to a reusable component repository. If you need a component, you may look into the repository for those components and then add them into your project or application. For example, you can create an application module for a domain and package it to be used as the data model project in several different applications. Or, if your application will be consuming components, you may be able to load a page template component from a repository of ADF Library JARs to create common look and feel pages. Then you can put your page flow together by stringing together several task flow components pulled from the library. An ADF Library JAR contains ADF components and does not, and cannot, contain other JARs. It should not be confused with the JDeveloper library, Java EE library, or Oracle WebLogic shared library. Reusable Component Description Data Control Any data control can be packaged into an ADF Library JAR. Some of the data controls supported by Oracle ADF include application modules, Enterprise JavaBeans, web services, URL services, JavaBeans, and placeholder data controls. Application Module When you are using ADF Business Components and you generate an application module, an associated application module data control is also generated. When you package an application module data control, you also package up the ADF Business Components associated with that application module. The relevant entity objects, view objects, and associations will be a part of the ADF Library JAR and available for reuse. Business Components Business components are the entity objects, view objects, and associations used in the ADF Business Components data model project. You can package business components by themselves or together with an application module. Task Flows & Task Flow Templates Task flows can be packaged into an ADF Library JAR for reuse. If you drop a bounded task flow that uses page fragments, JDeveloper adds a region to the page and binds it to the dropped task flow. ADF bounded task flows built using pages can be dropped onto pages. The drop will create a link to call the bounded task flow. A task flow call activity and control flow will automatically be added to the task flow, with the view activity referencing the page. If there is more than one existing task flow with a view activity referencing the page, it will prompt you to select the one to automatically add a task flow call activity and control flow. If an ADF task flow template was created in the same project as the task flow, the ADF task flow template will be included in the ADF Library JAR and will be reusable. Page Templates You can package a page template and its artifacts into an ADF Library JAR. If the template uses image files and they are included in a directory within your project, these files will also be available for the template during reuse. Declarative Components You can create declarative components and package them for reuse. The tag libraries associated with the component will be included and loaded into the consuming project. You can also package up projects that have several different reusable components if you expect that more than one component will be consumed. For example, you can create a project that has both an application module and a bounded task flow. When this ADF Library JAR file is consumed, the application will have both the application module and the task flow available for use. You can package multiple components into one JAR file, or you can package a single component into a JAR file. Oracle ADF and JDeveloper give you the option and flexibility to create reusable components that best suit you and your organization. You create a reusable component by using JDeveloper to package and deploy the project that contains the components into a ADF Library JAR file. You use the components by adding that JAR to the consuming project. At design time, the JAR is added to the consuming project's class path and so is available for reuse. At runtime, the reused component runs from the JAR file by reference.

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• Clone a VirtualBox Machine

  I just installed VirtualBox, which I want to try out based on recommendations from peers for running a server from within my Windows 7 x64 OS.  Ive never used VirtualBox, so Im certainly no expert at it, but I did want to share my experience with it thus far.  Specifically, my intention is to create a couple of virtual machines.  One I intend to use as a build server, for which a virtual machine makes sense because I can easily move it around as needed if there are hardware issues (its worth noting my need for setting up a build server at the moment is a result of a disk failure on the old build server).  The other VM I want to set up will act as a proxy server for the issue tracking system were using at Code Project, Axosoft OnTime.  They have a Remote Server application for this purpose, and since the OnTime install is 300 miles away from my location, the Remote Server should speed up my use of the OnTime client by limiting the chattiness with the database (at least, thats the hope). So, I need two VMs, and Im lazy.  I dont want to have to install the OS and such twice.  No problem, it should be simple to clone a virtualbox machine, or clone a virtualbox hard drive, right?  Well unfortunately, if you look at the UI for VirtualBox, theres no such command.  Youre left wondering How do I clone a VirtualBox machine? or the slightly related How do I clone a VirtualBox hard drive? If youve used VirtualPC, then you know that its actually pretty easy to copy and move around those VMs.  Not quite so easy with VirtualBox.  Finding the files is easy, theyre located in your user folder within the .VirtualBox folder (possibly within a HardDisks folder).  The disks have a .vdi extension and will be pretty large if youve installed anything.  The one shown here has just Windows Server 2008 R2 installed on it nothing else. If you copy the .vdi file and rename it, you can use the Virtual Media Manager to view it and you can create a new machine and choose the new drive to attach to.  Unfortunately, if you simply make a copy of the drive, this wont work and youll get an error that says something to the effect of: Cannot register the hard disk PATH with UUID {id goes here} because a hard disk PATH2 with UUID {same id goes here} already exists in the media registry (PATH to XML file). There are command line tools you can use to do this in a way that avoids this error.  Specifically, the c:\Program File\Sun\VirtualBox\VBoxManage.exe program is used for all command line access to VirtualBox, and to copy a virtual disk (.vdi file) you would call something like this: VBoxManage clonehd Disk1.vdi Disk1_Copy.vdi However, in my case this didnt work.  I got basically the same error I showed above, along with some debug information for line 628 of VBoxManageDisk.cpp.  As my main task was not to debug the C++ code used to write VirtualBox, I continued looking for a simple way to clone a virtual drive.  I found it in this blog post. The Secret setvdiuuid Command VBoxManage has a whole bunch of commands you can use with it just pass it /? to see the list.  However, it also has a special command called internalcommands that opens up access to even more commands.  The one thats interesting for us here is the setvdiuuid command.  By calling this command and passing in the file path to your vdi file, it will reset the UUID to a new (random, apparently) UUID.  This then allows the virtual media manager to cope with the file, and lets you set up new machines that reference the newly UUIDd virtual drive.  The full command line would be: VBoxManage internalcommands setvdiuuid MyCopy.vdi The following screenshot shows the error when trying clonehd as well as the successful use of setvdiuuid. Summary Now that I can clone machines easily, its a simple matter to set up base builds of any OS I might need, and then fork from there as needed.  Hopefully the GUI for VirtualBox will be improved to include better support for copying machines/disks, as this is Im sure a very common scenario. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• CS, SE, HCI, Information Science, Please recommendation for further education of the former performing art manager seeking career in IT industries? [on hold]

  - by Baek Seungjoo

  IT specialists there J Thank you very much for your collective efforts here, and I got huge help reading your professional comments and advices on each questions I have searched so far! This time, I would like to ask for your practical advices or recommendation on what I am struggling on at this moment. I am currently seeking higher education for my career transition from performing art manager and director to “IT software and/or service development and management specialist”. However, as this field is quite new to me, and there are lots of different work positions, I have no idea which grad major I better pursue in order to get qualification. Of course I know this question could sounds wired as it is kind of personal choice. But my lack of understanding on how IT software companies work in general, your practical and experience-based advice will be great help to me, who spent more than two months of self-research on net. OK. Before my question, here is my plan and history, which are quite different from those currently in IT industry I think… 1) Target Firstly, get career transition into IT service or products companies and get experiences. Eventually, pursue IT entrepreneurship in combination with my arts and cultural production and business expertise. 2) Background Career: performing arts director and manager in theatre-based scale opera and musical Art education in youth BA in literature and Chinese studies (Art & Humanities) MA in Cultural & Creative Industries (Art & Humanities) – dissertation with focus on digital prosumption and the lived experience of the prosumer. (a qualitative research on the agents in the digital world) 2) Personally Huge interest in IT hardware and software, and their trend. Skills to build up, repair, tune PCs -of course this is no more than personal hobby, but shows my interests in this field. 4) Problem Encounter a question “So, what do you think you can contribute practically in this position”. This question turn me down everytime I go through job interviews, and I decided more education in the relevant area. Here are my questions. 1) In terms of work positions in IT software companies, I wonder if I can put the comparison of what “Artists” is to “Arts Manager or Director” is what “Developer” is to “Product Manager”. (Of course, this stereotypical division of Artist-Art Manager is out of sense because the domain overlaps to some extent, and is blurring at least in my field, and they are in different contexts, but just speaking easily.) Normally, artist comes with special arts educations, and they live in their own world of artistic inspiration and creation, and they feel alive in practice and on stages. Meanwhile, from the point of staging and managing productions, the role of art manager is critical as well. Our role cares how the production appeals to the audience in effective way, how to make profit and future sustainable management through that, how to set up future strategy in consideration of the external conditions such as political and social circumstances, audience trend and level, other production trends from on-going and historical perspectives, how and what the production make voice to the society from political, economic, humanitarian stances. So, we need keen eyes on economic, political, and societal environment, have to understand human-being and their desires, must know how to make presentation and attract investors, must have sense in managing and fighting over the limited financial resource, how to extend networking and so on. It is common that the two agents create productions in collaboration (normally not in that ideal way but in conflict and fight though J ). So, we need to know each other’s expertise to some extent, for better production. What are the work positions in IT software industries equivalent to the role of “art manager” in performing arts? From my view, considering developers come with special education in the world of computer science, software engineering, or others (self-education sometimes), and they express themselves with the arts of coding, computer languages on the black screen, and make sort of their artistic production online to the audience, I guess there might be someone who collaborate with developers in creating, managing, and launching IT services or products. 2) Which education among CS, SE, HCI, Information Science, is needed for those seeking such work position? Especially for person like me. (At this moment, Information Science has the highest possibility to get in, since I lack Calculus and Math in undergrad educaiton. But please let me know irrespective of this concern, I think there are ways to back it up if CS or SE education needed in my case) 3) Which field between Information Science and HCI can be more practical background regarding job hungting? And which of them have more demands in job market? AS I checked, HCI is more close to CS than IS in its focus of study area. Thank you very much for your patience reading such a long inquiry, and I appreciate to your efforts in advance. Have a nice day in this beautiful summer.

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• What Counts for A DBA - Logic

  - by drsql

  "There are 10 kinds of people in the world. Those who will always wonder why there are only two items in my list and those who will figured it out the first time they saw this very old joke."  Those readers who will give up immediately and get frustrated with me for not explaining it to them are not likely going to be great technical professionals of any sort, much less a programmer or administrator who will be constantly dealing with the common failures that make up a DBA's day.  Many of these people will stare at this like a dog staring at a traffic signal and still have no more idea of how to decipher the riddle. Without explanation they will give up, call the joke "stupid" and, feeling quite superior, walk away indignantly to their job likely flipping patties of meat-by-product. As a data professional or any programmer who has strayed  to this very data-oriented blog, you would, if you are worth your weight in air, either have recognized immediately what was going on, or felt a bit ignorant.  Your friends are chuckling over the joke, but why is it funny? Unfortunately you left your smartphone at home on the dresser because you were up late last night programming and were running late to work (again), so you will either have to fake a laugh or figure it out.  Digging through the joke, you figure out that the word "two" is the most important part, since initially the joke mentioned 10. Hmm, why did they spell out two, but not ten? Maybe 10 could be interpreted a different way?  As a DBA, this sort of logic comes into play every day, and sometimes it doesn't involve nerdy riddles or Star Wars folklore.  When you turn on your computer and get the dreaded blue screen of death, you don't immediately cry to the help desk and sit on your thumbs and whine about not being able to work. Do that and your co-workers will question your nerd-hood; I know I certainly would. You figure out the problem, and when you have it narrowed down, you call the help desk and tell them what the problem is, usually having to explain that yes, you did in fact try to reboot before calling.  Of course, sometimes humility does come in to play when you reach the end of your abilities, but the ‘end of abilities’ is not something any of us recognize readily. It is handy to have the ability to use logic to solve uncommon problems: It becomes especially useful when you are trying to solve a data-related problem such as a query performance issue, and the way that you approach things will tell your coworkers a great deal about your abilities.  The novice is likely to immediately take the approach of  trying to add more indexes or blaming the hardware. As you become more and more experienced, it becomes increasingly obvious that performance issues are a very complex topic. A query may be slow for a myriad of reasons, from concurrency issues, a poor query plan because of a parameter value (like parameter sniffing,) poor coding standards, or just because it is a complex query that is going to be slow sometimes. Some queries that you will deal with may have twenty joins and hundreds of search criteria, and it can take a lot of thought to determine what is going on.  You can usually figure out the problem to almost any query by using basic knowledge of how joins and queries work, together with the help of such things as the query plan, profiler or monitoring tools.  It is not unlikely that it can take a full day’s work to understand some queries, breaking them down into smaller queries to find a very tiny problem. Not every time will you actually find the problem, and it is part of the process to occasionally admit that the problem is random, and everything works fine now.  Sometimes, it is necessary to realize that a problem is outside of your current knowledge, and admit temporary defeat: You can, at least, narrow down the source of the problem by looking logically at all of the possible solutions. By doing this, you can satisfy your curiosity and learn more about what the actual problem was. For example, in the joke, had you never been exposed to the concept of binary numbers, there is no way you could have known that binary - 10 = decimal - 2, but you could have logically come to the conclusion that 10 must not mean ten in the context of the joke, and at that point you are that much closer to getting the joke and at least won't feel so ignorant.

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• Coherence Data Guarantees for Data Reads - Basic Terminology

  - by jpurdy

  When integrating Coherence into applications, each application has its own set of requirements with respect to data integrity guarantees. Developers often describe these requirements using expressions like "avoiding dirty reads" or "making sure that updates are transactional", but we often find that even in a small group of people, there may be a wide range of opinions as to what these terms mean. This may simply be due to a lack of familiarity, but given that Coherence sits at an intersection of several (mostly) unrelated fields, it may be a matter of conflicting vocabularies (e.g. "consistency" is similar but different in transaction processing versus multi-threaded programming). Since almost all data read consistency issues are related to the concept of concurrency, it is helpful to start with a definition of that, or rather what it means for two operations to be concurrent. Rather than implying that they occur "at the same time", concurrency is a slightly weaker statement -- it simply means that it can't be proven that one event precedes (or follows) the other. As an example, in a Coherence application, if two client members mutate two different cache entries sitting on two different cache servers at roughly the same time, it is likely that one update will precede the other by a significant amount of time (say 0.1ms). However, since there is no guarantee that all four members have their clocks perfectly synchronized, and there is no way to precisely measure the time it takes to send a given message between any two members (that have differing clocks), we consider these to be concurrent operations since we can not (easily) prove otherwise. So this leads to a question that we hear quite frequently: "Are the contents of the near cache always synchronized with the underlying distributed cache?". It's easy to see that if an update on a cache server results in a message being sent to each near cache, and then that near cache being updated that there is a window where the contents are different. However, this is irrelevant, since even if the application reads directly from the distributed cache, another thread update the cache before the read is returned to the application. Even if no other member modifies a cache entry prior to the local near cache entry being updated (and subsequently read), the purpose of reading a cache entry is to do something with the result, usually either displaying for consumption by a human, or by updating the entry based on the current state of the entry. In the former case, it's clear that if the data is updated faster than a human can perceive, then there is no problem (and in many cases this can be relaxed even further). For the latter case, the application must assume that the value might potentially be updated before it has a chance to update it. This almost aways the case with read-only caches, and the solution is the traditional optimistic transaction pattern, which requires the application to explicitly state what assumptions it made about the old value of the cache entry. If the application doesn't want to bother stating those assumptions, it is free to lock the cache entry prior to reading it, ensuring that no other threads will mutate the entry, a pessimistic approach. The optimistic approach relies on what is sometimes called a "fuzzy read". In other words, the application assumes that the read should be correct, but it also acknowledges that it might not be. (I use the qualifier "sometimes" because in some writings, "fuzzy read" indicates the situation where the application actually sees an original value and then later sees an updated value within the same transaction -- however, both definitions are roughly equivalent from an application design perspective). If the read is not correct it is called a "stale read". Going back to the definition of concurrency, it may seem difficult to precisely define a stale read, but the practical way of detecting a stale read is that is will cause the encompassing transaction to roll back if it tries to update that value. The pessimistic approach relies on a "coherent read", a guarantee that the value returned is not only the same as the primary copy of that value, but also that it will remain that way. In most cases this can be used interchangeably with "repeatable read" (though that term has additional implications when used in the context of a database system). In none of cases above is it possible for the application to perform a "dirty read". A dirty read occurs when the application reads a piece of data that was never committed. In practice the only way this can occur is with multi-phase updates such as transactions, where a value may be temporarily update but then withdrawn when a transaction is rolled back. If another thread sees that value prior to the rollback, it is a dirty read. If an application uses optimistic transactions, dirty reads will merely result in a lack of forward progress (this is actually one of the main risks of dirty reads -- they can be chained and potentially cause cascading rollbacks). The concepts of dirty reads, fuzzy reads, stale reads and coherent reads are able to describe the vast majority of requirements that we see in the field. However, the important thing is to define the terms used to define requirements. A quick web search for each of the terms in this article will show multiple meanings, so I've selected what are generally the most common variations, but it never hurts to state each definition explicitly if they are critical to the success of a project (many applications have sufficiently loose requirements that precise terminology can be avoided).

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• How to fix Ubuntu 12.04.3 boot to black screen full of errors in white text, after upgrading on dell inspiron 1501

  - by Ibuntu

  I am running a Dell Inspiron 1501 I use Linux only. No Microsoft or Apple operating systems (or really anything closed-source). I've only been using Linux for a little over a year but I'm starting to gain a comfortable level of familiarity with the system and terminology. I've been having some issues with Quantel Quetzal and Raring Ringtail, especially with older hardware, so I opted to install Ubuntu 12.04.3 Precise Pangolin on the Inspiron 1501. I checked my MD5 sum after downloading my ISO and all was good. I have in fact used this iso/dvd to install Precise Pangolin successfully on a few other systems (some of which are even older than this laptop). Install goes fine. The wireless card doesn't work out of the box but this is a known issue which is fairly easy to fix. So, first thing I did was open up a terminal and run sudo apt-get update && sudo apt-get upgrade which, part way through, crashed (I assume lightdm and possibly X) and took me to a black screen filled with white lines of text that were either errors or just the ouputs of commands. The reason I say that is because I was unable to gleam any useful information from the output on the screen. I did take a picture however and will post a link. After that, every time I boot the system it goes right to that black screen posting all the error messages or output in white text. I never get a purple Ubuntu splash, so from what I can tell after reading this wiki article: https://wiki.ubuntu.com/X/Troubleshooting/BlankScreen That means that after the kernel is selected, it is unable to correctly implement the settings it needs. If the purple splash never shows, the frame buffer was never set correctly right? This leads me to believe that it could be a kernel issue? The wiki suggested to try and pinpoint the issue by rolling back kernels until I find one that works. Is this my best option? I think I'm going to give it a try anyways and will let everyone know if I am able to solve the issue this way. I have since done a few reinstalls and some trouble-shooting including a couple hours scouring the net for anyone with any kind of similar issue. Most of the issues I could find involved getting a black screen after login and none of them said anything about any information output on this black screen. My reinstalls have taught me that there is no issue updating, but as soon as I run sudo apt-get upgrade my system goes to the black screen and every time I boot it up it does the same thing. The only way to fix is by reinstall. I never get any ability to log in. After a hard power off to the laptop (because I cannot use ctrl+alt+del to reboot) when it boots again it goes to the grub boot menu and I can select between regular boot, recovery mode and the two memtest options. I never tried the memtest options but the other two both lead to the same black screen. Some people having a black/blank screen issue claim to have fixed it by using 12.10 or 13.04 but I believe they were having a different issue where they got a black/blank screen after logging in. I think I will still give these images a try, but mostly figured I would just wait another day or two for 13.10. Other things I figured I would try from the following three articles: After logging in, there's a black screen and my cursor, nothing else! in Ubuntu 12.10 Black Screen on Login After Upgrading to 12.04 I can't get to the login screen include opening a terminal using ctrl+alt+f1 and trying a variety of reseting unity, x settings, lightdm (or switching to gdm); but I doubt this will work or that I will even be able to access a terminal. I'm pretty sure the whole system is stuck after it loads the last line on the black screen. I will try these things and post more information when I have. Hopefully someone has an idea in the meantime and I will keep checking back trying to find a solution. Thank you. Here are 3 different pictures of the error message. I had to take with my phone: http://ubuntuone.com/album/0TBBkxmVajJIQQtoN9mVdN

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• Windows Phone 8 Launch Event Summary

  - by Tim Murphy

  Today was the official coming out party for Windows Phone 8.  Below is a summary of the launch event.  There is a lot here to stay with me. They started with a commercial staring Joe Belfiore show how his Windows Phone 8 was personal too him which highlights something I think Microsoft has done well over the last couple of event: spotlight how Windows Phone is a different experience from other smartphones.  Joe actually called iPhone and Android “tired old metaphors" and explained that the idea around Windows Phone was to “reinvent the smartphone around you” as “the most personal smartphone operating system”.  The is the message that they need to drive home in their adds. The only real technical aspect we found out was that they have optimized the operating system around the dual core Qualcomm Snapdragon chip set.  It seems like all of the other hardware goodies had already been announced.  The remainder of the event was centered around new features of the OS and app announcements. So what are we getting?  The integrated features included lock screen live tile, Data Sense, Rooms and Kids corner.  There wasn’t a lot of information about it, but Joe also talked about apps not just having live tiles, but being live apps that could integrate with wallet and the hub. The lock screen will now be able to be personalized with live tile data or even a photo slide show.  This gives the lock screen an even better ability to give you the information you want to know before you even unlock the phone. The Kids Corner allows you as a parent to setup an area on your phone that you kids can go into an use it without disturbing your apps.  They can play games or use apps that you have designated and will only see those apps.  It even has a special lock screen gesture just for the kids corner. Rooms allow you to organize your phone around the groups of people in your life.  You get a shared calendar, a room wall as well as shared notes beyond just being able to send messages to a group.  You can also invite people not on the Windows Phone platform to access an online version of the room. Data Sense is a new feature that gives you better control and understanding of your data plan usage.  You can see which applications are using data and it can automatically adjust they way your phone behaves as you get close to your data limit. Add to these features the fact that the entire Windows ecosystem is integrated with SkyDrive and you have an available anywhere experience that is unequaled by any other platform.  Your document, photos and music are available on your Windows Phone, Window 8 device and Xbox.  SkyDrive also doesn’t limit how long you can keep files like the competing cloud platforms and give more free storage. It was interesting the way they made the launch event more personal.  First Joe brought out his own kids to demo the Kids Corner.  They followed this up by bringing out Jessica Alba to discuss her experience on the Windows Phone 8.  They need to keep putting a face on the product instead of just showing features as a cold list. Then we get to apps.  We knew that the new Skype was coming, but we found out that it was created in such a way that it can receive calls without running consistently in the background which would eat up battery.  This announcement was follow by the coming Facebook app that is optimized for Windows Phone 8.  As a matter of fact they indicated that just after launch the marketplace would have 46 out of the top 50 apps used by all smartphone platforms.  In a rational world this tide with over 120,000 apps currently in the marketplace there should be no more argument about the Windows Phone ecosystem. For those of us who develop for Windows Phone and weren’t on the early adoption program will finally get access to the SDK tomorrow after an announcement at Build (more waiting).  Perhaps we will get a few new features then. In the end I wouldn’t say there were any huge surprises, but I am really excited about getting my hands on the devices next month and starting to develop.  Stay tuned. del.icio.us Tags: Windows Phone,Windows Phone 8,Winodws Phone 8 Launch,Joe Belfiore,Jessica Alba

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• No More NCrunch For Me

  - by Steve Wilkes

  When I opened up Visual Studio this morning, I was greeted with this little popup: NCrunch is a Visual Studio add-in which runs your tests while you work so you know if and when you've broken anything, as well as providing coverage indicators in the IDE and coverage metrics on demand. It recently went commercial (which I thought was fair enough), and time is running out for the free version I've been using for the last couple of months. From my experiences using NCrunch I'm going to let it expire, and go about my business without it. Here's why. Before I start, let me say that I think NCrunch is a good product, which is to say it's had a positive impact on my programming. I've used it to help test-drive a library I'm making right from the start of the project, and especially at the beginning it was very useful to have it run all my tests whenever I made a change. The first problem is that while that was cool to start with, it’s recently become a bit of a chore. Problems Running Tests NCrunch has two 'engine modes' in which it can run tests for you - it can run all your tests when you make a change, or it can figure out which tests were impacted and only run those. Unfortunately, it became clear pretty early on that that second option (which is marked as 'experimental') wasn't really working for me, so I had to have it run everything. With a smallish number of tests and while I was adding new features that was great, but I've now got 445 tests (still not exactly loads) and am more in a 'clean and tidy' mode where I know that a change I'm making will probably only affect a particular subset of the tests. With that in mind it's a bit of a drag sitting there after I make a change and having to wait for NCrunch to run everything. I could disable it and manually run the tests I know are impacted, but then what's the point of having NCrunch? If the 'impacted only' engine mode worked well this problem would go away, but that's not what I found. Secondly, what's wrong with this picture? I've got 445 tests, and NCrunch has queued 455 tests to run. So it's queued duplicate tests - in this quickly-screenshotted case 10, but I've seen the total queue get up over 600. If I'm already itchy waiting for it to run all my tests against a change I know only affects a few, I'm even itchier waiting for it to run a lot of them twice. Problems With Code Coverage NCrunch marks each line of code with a dot to say if it's covered by tests - a black dot says the line isn't covered, a red dot says it's covered but at least one of the covering tests is failing, and a green dot means all the covering tests pass. It also calculates coverage statistics for you. Unfortunately, there's a couple of flaws in the coverage. Firstly, it doesn't support ExcludeFromCodeCoverage attributes. This feature has been requested and I expect will be included in a later release, but right now it doesn't. So this: ...is counted as a non-covered line, and drags your coverage statistics down. Hmph. As well as that, coverage of certain types of code is missed. This: ...is definitely covered. I am 100% absolutely certain it is, by several tests. NCrunch doesn't pick it up, down go my coverage statistics. I've had NCrunch find genuinely uncovered code which I've been able to remove, and that's great, but what's the coverage percentage on this project? Umm... I don't know. Conclusion None of these are major, tool-crippling problems, and I expect NCrunch to get much better in future releases. The current version has some great features, like this: ...that's a line of code with a failing test covering it, and NCrunch can run that failing test and take me to that line exquisitely easily. That's awesome! I'd happily pay for a tool that can do that. But here's the thing: NCrunch (currently) costs $159 (about £100) for a personal licence and $289 (about £180) for a commercial one. I'm not sure which one I'd need as my project is a personal one which I'm intending to open-source, but I'm a professional, self-employed developer, but in any case - that seems like a lot of money for an imperfect tool. If it did everything it's advertised to do more or less perfectly I'd consider it, but it doesn't. So no more NCrunch for me.

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• How to Point sprite's direction towards Mouse or an Object [duplicate]

  - by Irfan Dahir

  This question already has an answer here: Rotating To Face a Point 1 answer I need some help with rotating sprites towards the mouse. I'm currently using the library allegro 5.XX. The rotation of the sprite works but it's constantly inaccurate. It's always a few angles off from the mouse to the left. Can anyone please help me with this? Thank you. P.S I got help with the rotating function from here: http://www.gamefromscratch.com/post/2012/11/18/GameDev-math-recipes-Rotating-to-face-a-point.aspx Although it's by javascript, the maths function is the same. And also, by placing: if(angle < 0) { angle = 360 - (-angle); } doesn't fix it. The Code: #include <allegro5\allegro.h> #include <allegro5\allegro_image.h> #include "math.h" int main(void) { int width = 640; int height = 480; bool exit = false; int shipW = 0; int shipH = 0; ALLEGRO_DISPLAY *display = NULL; ALLEGRO_EVENT_QUEUE *event_queue = NULL; ALLEGRO_BITMAP *ship = NULL; if(!al_init()) return -1; display = al_create_display(width, height); if(!display) return -1; al_install_keyboard(); al_install_mouse(); al_init_image_addon(); al_set_new_bitmap_flags(ALLEGRO_MIN_LINEAR | ALLEGRO_MAG_LINEAR); //smoother rotate ship = al_load_bitmap("ship.bmp"); shipH = al_get_bitmap_height(ship); shipW = al_get_bitmap_width(ship); int shipx = width/2 - shipW/2; int shipy = height/2 - shipH/2; int mx = width/2; int my = height/2; al_set_mouse_xy(display, mx, my); event_queue = al_create_event_queue(); al_register_event_source(event_queue, al_get_mouse_event_source()); al_register_event_source(event_queue, al_get_keyboard_event_source()); //al_hide_mouse_cursor(display); float angle; while(!exit) { ALLEGRO_EVENT ev; al_wait_for_event(event_queue, &ev); if(ev.type == ALLEGRO_EVENT_KEY_UP) { switch(ev.keyboard.keycode) { case ALLEGRO_KEY_ESCAPE: exit = true; break; /*case ALLEGRO_KEY_LEFT: degree -= 10; break; case ALLEGRO_KEY_RIGHT: degree += 10; break;*/ case ALLEGRO_KEY_W: shipy -=10; break; case ALLEGRO_KEY_S: shipy +=10; break; case ALLEGRO_KEY_A: shipx -=10; break; case ALLEGRO_KEY_D: shipx += 10; break; } }else if(ev.type == ALLEGRO_EVENT_MOUSE_AXES) { mx = ev.mouse.x; my = ev.mouse.y; angle = atan2(my - shipy, mx - shipx); } // al_draw_bitmap(ship,shipx, shipy, 0); //al_draw_rotated_bitmap(ship, shipW/2, shipH/2, shipx, shipy, degree * 3.142/180,0); al_draw_rotated_bitmap(ship, shipW/2, shipH/2, shipx, shipy,angle, 0); //I directly placed the angle because the allegro library calculates radians, and if i multiplied it by 180/3. 142 the rotation would go hawire, not would, it actually did. al_flip_display(); al_clear_to_color(al_map_rgb(0,0,0)); } al_destroy_bitmap(ship); al_destroy_event_queue(event_queue); al_destroy_display(display); return 0; } EDIT: This was marked duplicate by a moderator. I'd like to say that this isn't the same as that. I'm a total beginner at game programming, I had a view at that other topic and I had difficulty understanding it. Please understand this, thank you. :/ Also, while I was making a print of what the angle is I got this... Here is a screenshot:http://img34.imageshack.us/img34/7396/fzuq.jpg Which is weird because aren't angles supposed to be 360 degrees only?

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• The Dreaded Startup Repair Loop on Win 7

  - by HighAltitudeCoder

  For most people, upgrading to Windows 7 has been a relatively painless process.  Not me.  I am in the unlucky 1% or less who had a somewhat less pleasant experience.  First, I cloned my entire onto a larger (and much faster) solid state hard drive, only experiencing minimal problems. Then, I bought the Retail version of Windows 7 Ultimate, took a deep breath and... oh yeah, I almost forgot - BACK UP THE COMPUTER.  The next morning I upgraded to Win 7 and everything seemed fine, until... I rebooted the system, the nice Windows 7 launch graphics come up, it's about to launch and AWWW, are you kidding me?!?!  Back to the BIOS splash screen?  Next comes the sequence of failure - attempt repair - unable to repair - do you want to wipe your hard drive decisions. Because I purchased the retail version, a number is provided where I could call Microsoft Tech support.  When I did, they instructed me to click "Install" from my installation CD, which did not work.  When I tried the "Upgrade" option, it reaches an impasse, telling you that yoiu have a newer version of Win 7, and thus cannot Upgrade.  If you choose "Install" you willl lose everything... files, programs, EVERYTHING.  Or at least this is what it tells you.  I was not willing to take the risk. To make things worse, I had installed a new antivirus software application before I realized my system was unstable (Trend Micro Titanium Internet Security), and this was causing additional problems. One interesting thing, and the only saving grace as it turns out, was that my system WOULD successfully reboot into the OS if I chose to restart it, rather than shut it down.  If I chose to shut down, I would have to go through the loop again until I was given the option to restart. As it turned out, I needed to update my BIOS.  I assumed that since I had updated my BIOS a long time ago to settings that were stable under Windows Vista Ultimate x64, I incorrectly expected Win 7 to adopt the same settings and didn't expect there to be any problems.  WRONG. My BIOS had a setting to halt the boot cycle if various kinds of errors were detected.  Windows Vista didn't care about this, but forget it under Windows 7.  I turned immediately corrected that BIOS setting.  Next, there were the two separate BIOS settings: enable USB mouse and enable USB keyboard.  The only sequence of events that would work were to start my reboot process over from stratch with a hard-wired non-usb keyboard and mouse.  Whent the system booted under these settings, it doesn't detect any errors due to either the mouse or keyboard, and actually booted for the first time in a long while (let me tell ya, that's an amazing experience after fiddling with settings for two entire weekends!) Next step: leave your old mouse and keyboard connected, but also connect your other two devices (mouse, keyboard) that use USB connections.  During the boot cycle, the operating system will not fail due to missing requirements during startup, and it will then pick up the new drivers necessary to use your new hardware. If you think you are in the clear here, you are wrong.  The next VERY IMPORTANT step is to remember to change your settings in the BIOS upon next startup.  Specifically, yoiu will need ot change your BIOS to enable USB mouse and enable USB keyboard input.  If you don't, Windows will detect an incompatibility upon the next startup, and you will be stuck once again in the endless cycle of reboot/Startup Repair/reboot/Startup Repair, without ever reaching a successful boot. Here's the thing - the BIOS and the drivers registered in Win 7 need to match.  If they don't, you're going to lose another weekend worrying and fiddling, all the while wondering if you've permanently damaged your hard drive beyond repair. (Sigh).  In the end, things worked out.  I must note that it is saddening to see how many posts there are out there that recommend just doing a clean install, as if it's the only option.  How many countless poor souls have lost their data, their backups, their pictures and videos, all for nothing other than the fact that the person giving advice just didn't know what to do at that point? My advice to you, try having a look at your BIOS settings first and making sure Win 7 can find your BIOS settings, and also disabling in your BIOS anything that might halt your system boot-up process if it encounters errors.

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• What's New in Oracle VM VirtualBox 4.2?

  - by Fat Bloke

  A year is a long time in the IT industry. Since the last VirtualBox feature release, which was a little over a year ago, we've seen: new releases of cool new operating systems, such as Windows 8, ChromeOS, and Mountain Lion; we've seen a myriad of new Linux releases from big Enterprise class distributions like Oracle 6.3, to accessible desktop distros like Ubuntu 12.04 and Fedora 17; and we've also seen the spec of a typical PC or laptop double in power. All of these events have influenced our new VirtualBox version which we're releasing today. Here's how... Powerful hosts  One of the trends we've seen is that as the average host platform becomes more powerful, our users are consistently running more and more vm's. Some of our users have large libraries of vm's of various vintages, whilst others have groups of vm's that are run together as an assembly of the various tiers in a multi-tiered software solution, for example, a database tier, middleware tier, and front-ends.  So we're pleased to unveil a more powerful VirtualBox Manager to address the needs of these users: VM Groups Groups allow you to organize your VM library in a sensible way, e.g.  by platform type, by project, by version, by whatever. To create groups you can drag one VM onto another or select one or more VM's and choose Machine...Group from the menu bar. You can expand and collapse groups to save screen real estate, and you can Enter and Leave a group (think iPad navigation here) by using the right and left arrow keys when groups are selected. But groups are more than passive folders, because you can now also perform operations on groups, rather than all the individual VMs. So if you have a multi-tiered solution you can start the whole stack up with just one click. Autostart Many VirtualBox users run dedicated services in their VMs, for example, running a Wiki. With these types of VM workloads, you really want the VM start up when the host machine boots up. So with 4.2 we've introduced a cross-platform Auto-start mechanism to allow you to treat VMs as host services. Headless VM Launching With VM's such as web servers, wikis, and other types of server-class workloads, the Console of the VM is pretty much redundant. For some time now VirtualBox has offered a separate launch mechanism for these VM's, namely the command-line interface commands VBoxHeadless or VBoxManage startvm ... --type headless commands. But with 4.2 we also allow you launch headless VMs from the Manager. Simply hold down Shift when launching the VM from the Manager.  It's that easy. But how do you stop a headless VM? Well, with 4.2 we allow you to Close the VM from the Manager. (BTW best to use the ACPI Shutdown method which allows the guest VM to close down gracefully.) Easy VM Creation For our expert users, the  New VM Wizard was a little tiresome, so now there's a faster 2-click VM creation mode. Just Hide the description when creating a new VM. Powerful VMs  As the hosts have become more powerful, so are the guests that are running inside them. Here are some of the 4.2 features to accommodate them: Virtual Network Interface Cards  With 4.2, it's now possible to create VMs with up to 36 NICs, when using the ICH9 chipset emulation. But with great power comes great responsibility (didn't Obi-Wan say something similar?), and so we have also introduced bandwidth limiting to prevent a rogue VM stealing the whole pipe. VLAN tagging Some of our users leverage VLANs extensively so we've enhanced the E1000 NICs to support this.  Processor Performance If you are running a CPU which supports Nested Paging (aka EPT in the Intel world) such as most of the Core i5 and i7 CPUs, or are running an AMD Bulldozer or later, you should see some performance improvements from our work with these processors. And while we're talking Processors, we've added support for some of the more modern VIA CPUs too. Powerful Automation Because VirtualBox runs atop a fully blown operating system, it makes sense to leverage the capabilities of the host to run scripts that can drive the guest VMs. Guest Automation was introduced in a prior release but with 4.2 we've revamped the APIs to allow a richer and more powerful set of operations to be executed by the guest. Check out the IGuest APIs in the VirtualBox Programming Guide and Reference (SDK). Powerful Platforms  All the hardcore engineering that has gone into 4.2 has been done for a purpose and that is to deliver a fast and powerful engine that can run almost any x86 OS because of the integrity of the virtualization. So we're pleased to add support for these platforms: Mac OS X "Mountain Lion"  Windows 8 Windows Server 2012 Ubuntu 12.04 (“Precise Pangolin”) Fedora 17 Oracle Linux 6.3  Here's the proof: We don't have time to go into the myriad of smaller improvements such as support for burning audio CDs from a guest, bi-directional clipboard control,  drag-and-drop of files into Linux guests, etc. so we'll leave that as an exercise for the user as soon as you've downloaded from the Oracle or community site and taken a peek at the User Guide. So all in all, a pretty solid release, one that we hope you'll enjoy discovering. - FB 

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• What are some concise and comprehensive introductory guide to unit testing for a self-taught programmer [closed]

  - by Superbest

  I don't have much formal training in programming and I have learned most things by looking up solutions on the internet to practical problems I have. There are some areas which I think would be valuable to learn, but which ended up both being difficult to learn and easy to avoid learning for a self-taught programmer. Unit testing is one of them. Specifically, I am interested in tests in and for C#/.NET applications using Microsoft.VisualStudio.TestTools in Visual Studio 2010 and/or 2012, but I really want a good introduction to the principles so language and IDE shouldn't matter much. At this time I'm interested in relatively trivial tests for small or medium sized programs (development time of weeks or months and mostly just myself developing). I don't necessarily intend to do test-driven development (I am aware that some say unit testing alone is supposed to be for developing features in TDD, and not an assurance that there are no bugs in the software, but unit testing is often the only kind of testing for which I have resources). I have found this tutorial which I feel gave me a decent idea of what unit tests and TDD looks like, but in trying to apply these ideas to my own projects, I often get confused by questions I can't answer and don't know how to answer, such as: What parts of my application and what sorts of things aren't necessarily worth testing? How fine grained should my tests be? Should they test every method and property separately, or work with a larger scope? What is a good naming convention for test methods? (since apparently the name of the method is the only way I will be able to tell from a glance at the test results table what works in my program and what doesn't) Is it bad to have many asserts in one test method? Since apparently VS2012 reports only that "an Assert.IsTrue failed within method MyTestMethod", and if MyTestMethod has 10 Assert.IsTrue statements, it will be irritating to figure out why a test is failing. If a lot of the functionality deals with writing and reading data to/from the disk in a not-exactly trivial fashion, how do I test that? If I provide a bunch of files as input by placing them in the program's directory, do I have to copy those files to the test project's bin/Debug folder now? If my program works with a large body of data and execution takes minutes or more, should my tests have it do the whole use all of the real data, a subset of it, or simulated data? If latter, how do I decide on the subset or how to simulate? Closely related to the previous point, if a class is such that its main operation happens in a state that is arrived to by the program after some involved operations (say, a class makes calculations on data derived from a few thousands of lines of code analyzing some raw data) how do I test just that class without inevitably ending up testing that class and all the other code that brings it to that state along with it? In general, what kind of approach should I use for test initialization? (hopefully that is the correct term, I mean preparing classes for testing by filling them in with appropriate data) How do I deal with private members? Do I just suck it up and assume that "not public = shouldn't be tested"? I have seen people suggest using private accessors and reflection, but these feel like clumsy and unsuited for regular use. Are these even good ideas? Is there anything like design patterns concerning testing specifically? I guess the main themes in what I'd like to learn more about are, (1) what are the overarching principles that should be followed (or at least considered) in every testing effort and (2) what are popular rules of thumb for writing tests. For example, at one point I recall hearing from someone that if a method is longer than 200 lines, it should be refactored - not a universally correct rule, but it has been quite helpful since I'd otherwise happily put hundreds of lines in single methods and then wonder why my code is so hard to read. Similarly I've found ReSharpers suggestions on member naming style and other things to be quite helpful in keeping my codebases sane. I see many resources both online and in print that talk about testing in the context of large applications (years of work, 10s of people or more). However, because I've never worked on such large projects, this context is very unfamiliar to me and makes the material difficult to follow and relate to my real world problems. Speaking of software development in general, advice given with the assumptions of large projects isn't always straightforward to apply to my own, smaller endeavors. Summary So my question is: What are some resources to learn about unit testing, for a hobbyist, self-taught programmer without much formal training? Ideally, I'm looking for a short and simple "bible of unit testing" which I can commit to memory, and then apply systematically by repeatedly asking myself "is this test following the bible of testing closely enough?" and then amending discrepancies if it doesn't.

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• IE9, LightSwitch Beta 2 and Zune HD: A Study in Risk Management?

  - by andrewbrust

  Photo by parl, 'Risk.’ Under Creative Commons Attribution-NonCommercial-NoDerivs License This has been a busy week for Microsoft, and for me as well.  On Monday, Microsoft launched Internet Explorer 9 at South by Southwest (SXSW) in Austin, TX.  That evening I flew from New York to Seattle.  On Tuesday morning, Microsoft launched Visual Studio LightSwitch, Beta 2 with a Go-Live license, in Redmond, and I had the privilege of speaking at the keynote presentation where the announcement was made.  Readers of this blog know I‘m a fan of LightSwitch, so I was happy to tell the app dev tools partners in the audience that I thought the LightSwitch extensions ecosystem represented a big opportunity – comparable to the opportunity when Visual Basic 1.0 was entering its final beta roughly 20 years ago.  On Tuesday evening, I flew back to New York (and wrote most of this post in-flight). Two busy, productive days.  But there was a caveat that impacts the accomplishments, because Monday was also the day reports surfaced from credible news agencies that Microsoft was discontinuing its dedicated Zune hardware efforts.  While the Zune brand, technology and service will continue to be a component of Windows Phone and a piece of the Xbox puzzle as well, speculation is that Microsoft will no longer be going toe-to-toe with iPod touch in the portable music player market. If we take all three of these developments together (even if one of them is based on speculation), two interesting conclusions can reasonably be drawn, one good and one less so. Microsoft is doubling down on technologies it finds strategic and de-emphasizing those that it does not.  HTML 5 and the Web are strategic, so here comes IE9, and it’s a very good browser.  Try it and see.  Silverlight is strategic too, as is SQL Server, Windows Azure and SQL Azure, so here comes Visual Studio LightSwitch Beta 2 and a license to deploy its apps to production.  Downloads of that product have exceeded Microsoft’s projections by more than 50%, and the company is even citing analyst firms’ figures covering the number of power-user developers that might use it. (I happen to think the product will be used by full-fledged developers as well, but that’s a separate discussion.) Windows Phone is strategic too…I wasn’t 100% positive of that before, but the Nokia agreement has made me confident.  Xbox as an entertainment appliance is also strategic.  Standalone music players are not strategic – and even if they were, selling them has been a losing battle for Microsoft.  So if Microsoft has consolidated the Zune content story and the ZunePass subscription into Xbox and Windows Phone, it would make sense, and would be a smart allocation of resources.  Essentially, it would be for the greater good. But it’s not all good.  In this scenario, Zune player customers would lose out.  Unless they wanted to switch to Windows Phone, and then use their phone’s battery for the portable media needs, they’re going to need a new platform.  They’re going to feel abandoned.  Even if Zune lives, there have been other such cul de sacs for customers.  Remember SPOT watches?  Live Spaces?  The original Live Mesh?  Microsoft discontinued each of these products.  The company is to be commended for cutting its losses, as admitting a loss isn’t easy.  But Redmond won’t be well-regarded by the victims of those decisions.  Instead, it gets black marks. What’s the answer?  I think it’s a bit like the 1980’s New York City “don’t block the box” gridlock rules: don’t enter an intersection unless you see a clear path through it.  If the light turns red and you’re blocking the perpendicular traffic, that’s your fault in judgment.  You get fined and get points on your license and you don’t get to shrug it off as beyond your control.  Accountability is key.  The same goes for Microsoft.  If it decides to enter a market, it should see a reasonable path through success in that market. Switching analogies, Microsoft shouldn’t make investments haphazardly, and it certainly shouldn’t ask investors to buy into a high-risk fund that is sold as safe and which offers only moderate returns.  People won’t continue to invest with a fund manager with a track record of over-zealous, imprudent, sub-prime investments.  The same is true on the product side for Microsoft, and not just with music players and geeky wrist watches.  It’s true of Web browsers, and line-of-business app dev tools, and smartphones, and cloud platforms and operating systems too.  When Microsoft is casual about its own risk, it raises risk for its customers, and weakens its reputation, market share and credibility.  That doesn’t mean all risk is bad, but it does mean no product team’s risk should be taken lightly. For mutual fund companies, it’s the CEO’s job to give his fund managers autonomy, but to make sure they’re conforming to a standard of rational risk management.  Because all those funds carry the same brand, and many of them serve the same investors. The same goes for Microsoft, its product portfolio, its executive ranks and its product managers.

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• Are there Negative Impact of opensource on commercial environment?

  - by Lostsoul

  I know this is not a good fit for Stack Overflow but wasn't sure if it was good for this site also so let me know if its not and I'll delete it. I love programming for fun but my role in my company is not technical. I have always loved the hacker culture and have been trying to drive that openness within my company from day one. My company has a very broad range of products and there are a few that are not strategic to us so I wanted to open source them (so we can focus on what makes us unique and open source the products that every firm has). Our industry does not open source(we would be the first firm to try this) and the feedback I'm getting from my management team is either 1) we'll destroy the industry or 2) all competitive commercial firms will unite against us and we'll be wiped out either way. I disagreed on both points because I think transparency will only grow our industry and our firm (think of McDonalds/KFC sharing their recipe openly, people may copy you, competitors may target you, but customers also may feel more comfortable buying your product. The value add, I believe, is in the delivery and experience not in hoarding the recipe). It's a big battle in my firm right now between the IT people who have seen the positive effects of sharing and the business people who think we'll be giving up everything (they prefer we sell parts we want to opensource, but in their defense this is standard when divesting something). Our industry is very secretive and I don't want to put anyone(even my competitors employees) out of a job yet I don't want to protect inefficient people by not being open with everyone. Yet I've seen so many amazing technologies created in interesting ways just by giving people freedom to take apart code and put it back together. I'm interested in hearing people's thoughts(doesn't have to be to my specific situation, I'm looking for the general lessons). Its a very stressful decision(but one I feel I must make) because if we go the open source route then there will be no going back. So what are your thoughts? Does open sourcing apply generally or is it only really applicable to software? Is it overall good for people in the industry and outside? I'm actually more interested in the negativeness effects(although positive are welcomed as well) Update: Long story short, although code is involved this is not so much about code as it is more about the idea of open sourcing. We are a mid sized quant hedge fund. We have some unique strategies but also have the standard long/short, arbitrage, global macro, etc.. funds. We are keeping the unique funds we have but the other stuff that everyone else has we are considering open sourcing (We have put in years of work & millions of dollars into. Our funds is pretty popular and our performance is either in first or second quartile so I suspect there will be interest but I don't know to what extent). The goal is not to get a community to work for us or anything, the goal is to let anyone who wants to tinker with it do so and create anything they want (it will not be part of our product line although I may unofficially allocate some our of staff's time to assist any community that grows). Although the code base is quite large, the value in this is the industry knowledge and approaches we have acquired (there are many books on artificial intelligence and quant trading but they are often years behind what's really going on as most firms forbid their staff from discussing what they are doing). We are also considering after we move our clients out to let the software still run and output the resulting portfolios for free as well so people can at least see the results(as long as we have avail. infrastructure). I think our main choices are, we can continue to fight for market share in a products that are becoming commoditized, we can shut the funds/products down(and keep the code but no one outside of our firm will ever learn from it) or we can open source it and let people do what they want. By open sourcing it, my idea is that the talent pool in the industry will grow because right now most of our hires have the same background (CFA, MBA, similar school, same experience,etc.. because we can't spend time training people so the industry 'standardizes' most people and thus the firms themselves start to look/act similar) but this may allow us to identify talent that has never been in the industry before (if we put a GPU license then as people learn from what we did, we can learn from what they do as well and maybe apply it to other areas of our firm). I see a lot of benefits but not many negatives while my peers at the company see the opposite.

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• C# XNA 4.0 multitextured cube

  - by chron

  So I am following this tutorial on how to draw a cube in XNA and I ran into a problem. Ok so my shader can only have texture right? I need to have a texture on the front and back of my cube. So I thought I could just have both textures stored in one texture. Problem is I do not know how to map out my UV coords to do so. (I tried dividing by 2 and such with no luck...). I am really new to this (not programming, just game development and some concepts), but how could I get UV coordinates for both halfs of the texture. private void ConstructCube(Vector3 Position,Vector3 Size) { _vertices = new VertexPositionNormalTexture[50]; // Calculate the position of the vertices on the top face. Vector3 topLeftFront = Position + new Vector3(-1.0f, 1.0f, -1.0f) * Size; Vector3 topLeftBack = Position + new Vector3(-1.0f, 1.0f, 1.0f) * Size; Vector3 topRightFront = Position + new Vector3(1.0f, 1.0f, -1.0f) * Size; Vector3 topRightBack = Position + new Vector3(1.0f, 1.0f, 1.0f) * Size; // Calculate the position of the vertices on the bottom face. Vector3 btmLeftFront = Position + new Vector3(-1.0f, -1.0f, -1.0f) * Size; Vector3 btmLeftBack = Position + new Vector3(-1.0f, -1.0f, 1.0f) * Size; Vector3 btmRightFront = Position + new Vector3(1.0f, -1.0f, -1.0f) * Size; Vector3 btmRightBack = Position + new Vector3(1.0f, -1.0f, 1.0f) * Size; // Normal vectors for each face (needed for lighting / display) Vector3 normalFront = new Vector3(0.0f, 0.0f, 1.0f) * Size; Vector3 normalBack = new Vector3(0.0f, 0.0f, -1.0f) * Size; Vector3 normalTop = new Vector3(0.0f, 1.0f, 0.0f) * Size; Vector3 normalBottom = new Vector3(0.0f, -1.0f, 0.0f) * Size; Vector3 normalLeft = new Vector3(-1.0f, 0.0f, 0.0f) * Size; Vector3 normalRight = new Vector3(1.0f, 0.0f, 0.0f) * Size; // UV texture coordinates Vector2 textureTopLeft = new Vector2(1.0f * Size.X, 0.0f * Size.Y); Vector2 textureTopRight = new Vector2(0.0f * Size.X, 0.0f * Size.Y); Vector2 textureBottomLeft = new Vector2(1.0f * Size.X, 1.0f * Size.Y); Vector2 textureBottomRight = new Vector2(0.0f * Size.X, 1.0f * Size.Y); // Add the vertices for the FRONT face. _vertices[0] = new VertexPositionNormalTexture(topLeftFront, normalFront, textureTopLeft); _vertices[1] = new VertexPositionNormalTexture(btmLeftFront, normalFront, textureBottomLeft); _vertices[2] = new VertexPositionNormalTexture(topRightFront, normalFront, textureTopRight); _vertices[3] = new VertexPositionNormalTexture(btmLeftFront, normalFront, textureBottomLeft); _vertices[4] = new VertexPositionNormalTexture(btmRightFront, normalFront, textureBottomRight); _vertices[5] = new VertexPositionNormalTexture(topRightFront, normalFront, textureTopRight); // Add the vertices for the BACK face. _vertices[6] = new VertexPositionNormalTexture(topLeftBack, normalBack, textureTopRight); _vertices[7] = new VertexPositionNormalTexture(topRightBack, normalBack, textureTopLeft); _vertices[8] = new VertexPositionNormalTexture(btmLeftBack, normalBack, textureBottomRight); _vertices[9] = new VertexPositionNormalTexture(btmLeftBack, normalBack, textureBottomRight); _vertices[10] = new VertexPositionNormalTexture(topRightBack, normalBack, textureTopLeft); _vertices[11] = new VertexPositionNormalTexture(btmRightBack, normalBack, textureBottomLeft); // Add the vertices for the TOP face. _vertices[12] = new VertexPositionNormalTexture(topLeftFront, normalTop, textureBottomLeft); _vertices[13] = new VertexPositionNormalTexture(topRightBack, normalTop, textureTopRight); _vertices[14] = new VertexPositionNormalTexture(topLeftBack, normalTop, textureTopLeft); _vertices[15] = new VertexPositionNormalTexture(topLeftFront, normalTop, textureBottomLeft); _vertices[16] = new VertexPositionNormalTexture(topRightFront, normalTop, textureBottomRight); _vertices[17] = new VertexPositionNormalTexture(topRightBack, normalTop, textureTopRight); // Add the vertices for the BOTTOM face. _vertices[18] = new VertexPositionNormalTexture(btmLeftFront, normalBottom, textureTopLeft); _vertices[19] = new VertexPositionNormalTexture(btmLeftBack, normalBottom, textureBottomLeft); _vertices[20] = new VertexPositionNormalTexture(btmRightBack, normalBottom, textureBottomRight); _vertices[21] = new VertexPositionNormalTexture(btmLeftFront, normalBottom, textureTopLeft); _vertices[22] = new VertexPositionNormalTexture(btmRightBack, normalBottom, textureBottomRight); _vertices[23] = new VertexPositionNormalTexture(btmRightFront, normalBottom, textureTopRight); // Add the vertices for the LEFT face. _vertices[24] = new VertexPositionNormalTexture(topLeftFront, normalLeft, textureTopRight); _vertices[25] = new VertexPositionNormalTexture(btmLeftBack, normalLeft, textureBottomLeft ); _vertices[26] = new VertexPositionNormalTexture(btmLeftFront, normalLeft, textureBottomRight ); _vertices[27] = new VertexPositionNormalTexture(topLeftBack, normalLeft, textureTopLeft); _vertices[28] = new VertexPositionNormalTexture(btmLeftBack, normalLeft, textureBottomLeft ); _vertices[29] = new VertexPositionNormalTexture(topLeftFront, normalLeft, textureTopRight ); // Add the vertices for the RIGHT face. _vertices[30] = new VertexPositionNormalTexture(topRightFront, normalRight, textureTopLeft); _vertices[31] = new VertexPositionNormalTexture(btmRightFront, normalRight, textureBottomLeft); _vertices[32] = new VertexPositionNormalTexture(btmRightBack, normalRight, textureBottomRight); _vertices[33] = new VertexPositionNormalTexture(topRightBack, normalRight, textureTopRight); _vertices[34] = new VertexPositionNormalTexture(topRightFront, normalRight, textureTopLeft); _vertices[35] = new VertexPositionNormalTexture(btmRightBack, normalRight, textureBottomRight); done = true; }

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• Plagued by multithreaded bugs

  - by koncurrency

  On my new team that I manage, the majority of our code is platform, TCP socket, and http networking code. All C++. Most of it originated from other developers that have left the team. The current developers on the team are very smart, but mostly junior in terms of experience. Our biggest problem: multi-threaded concurrency bugs. Most of our class libraries are written to be asynchronous by use of some thread pool classes. Methods on the class libraries often enqueue long running taks onto the thread pool from one thread and then the callback methods of that class get invoked on a different thread. As a result, we have a lot of edge case bugs involving incorrect threading assumptions. This results in subtle bugs that go beyond just having critical sections and locks to guard against concurrency issues. What makes these problems even harder is that the attempts to fix are often incorrect. Some mistakes I've observed the team attempting (or within the legacy code itself) includes something like the following: Common mistake #1 - Fixing concurrency issue by just put a lock around the shared data, but forgetting about what happens when methods don't get called in an expected order. Here's a very simple example: void Foo::OnHttpRequestComplete(statuscode status) { m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } So now we have a bug in which Shutdown could get called while OnHttpNetworkRequestComplete is occuring on. A tester finds the bug, captures the crash dump, and assigns the bug to a developer. He in turn fixes the bug like this. void Foo::OnHttpRequestComplete(statuscode status) { AutoLock lock(m_cs); m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { AutoLock lock(m_cs); m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } The above fix looks good until you realize there's an even more subtle edge case. What happens if Shutdown gets called before OnHttpRequestComplete gets called back? The real world examples my team has are even more complex, and the edge cases are even harder to spot during the code review process. Common Mistake #2 - fixing deadlock issues by blindly exiting the lock, wait for the other thread to finish, then re-enter the lock - but without handling the case that the object just got updated by the other thread! Common Mistake #3 - Even though the objects are reference counted, the shutdown sequence "releases" it's pointer. But forgets to wait for the thread that is still running to release it's instance. As such, components are shutdown cleanly, then spurious or late callbacks are invoked on an object in an state not expecting any more calls. There are other edge cases, but the bottom line is this: Multithreaded programming is just plain hard, even for smart people. As I catch these mistakes, I spend time discussing the errors with each developer on developing a more appropriate fix. But I suspect they are often confused on how to solve each issue because of the enormous amount of legacy code that the "right" fix will involve touching. We're going to be shipping soon, and I'm sure the patches we're applying will hold for the upcoming release. Afterwards, we're going to have some time to improve the code base and refactor where needed. We won't have time to just re-write everything. And the majority of the code isn't all that bad. But I'm looking to refactor code such that threading issues can be avoided altogether. One approach I am considering is this. For each significant platform feature, have a dedicated single thread where all events and network callbacks get marshalled onto. Similar to COM apartment threading in Windows with use of a message loop. Long blocking operations could still get dispatched to a work pool thread, but the completion callback is invoked on on the component's thread. Components could possibly even share the same thread. Then all the class libraries running inside the thread can be written under the assumption of a single threaded world. Before I go down that path, I am also very interested if there are other standard techniques or design patterns for dealing with multithreaded issues. And I have to emphasize - something beyond a book that describes the basics of mutexes and semaphores. What do you think? I am also interested in any other approaches to take towards a refactoring process. Including any of the following: Literature or papers on design patterns around threads. Something beyond an introduction to mutexes and semaphores. We don't need massive parallelism either, just ways to design an object model so as to handle asynchronous events from other threads correctly. Ways to diagram the threading of various components, so that it will be easy to study and evolve solutions for. (That is, a UML equivalent for discussing threads across objects and classes) Educating your development team on the issues with multithreaded code. What would you do?

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• Spring??Java EE 6?! ???????????????·????????Java Developers Workshop 2012 Summer????

  - by ???02

  ?Java EE 6??????????????????????????????????????/?????????????????????????Spring Framework?????????????????????????????????????????????????????????????????????????????? “Spring to Java EE 6”????·????????????????????Java EE 6????????????????????IT???????????????Java??????????????·???????????????8???????Java Developers Workshop 2012 Summer????????????????Best Practices for Migrating Spring to Java EE 6???????????????(???) ???????????????Spring Framework??Java EE 6???? ?????IT??????????????????·?????????????????? “Spring to Java EE 6”?????????????????????????????????????????????????????????????????????? ???????????Java?????????????????????????????????Java??????????????????????????????????????????????????100??Java??????????????????????????????????? ???????Java?????????????????1??????????·??????????????Java?????????????????????????????Java???????????????????·??????????????????·????????????Java????????????????????????????Java??????????????????????????????? ??????????????????????????????????????????????????Spring??Java EE 6??????????·???????Spring????????????????????Java EE 6?????????????????????????????????????????????????????Java EE 6??????????????????? 8???????Java Developers Workshop 2012 Summer??????????Java??????????????????????????????????Best Practices for Migrating Spring to Java EE 6??????????“Spring to Java EE 6”????????????????????????????“Spring to Java EE 6”??????????????????? Java??????????“Spring to Java EE 6”????·?????? ?????Spring??Java EE????????????????????????????????????????? Spring????????·?????????????J2EE Design and Development?????J2EE 1.4??????????????????????????Spring ?????????????????????????????? ???Spring???8?????????????????????????????????????Java EE?????????????????????????????????????????????????? ???????Java EE??????????????????????????Java EE??????????????????????????????????????????????????????????????????????????????????Spring????????Java EE 6???????????????????????????? ???????????????????????????????Java EE?Spring?????????????????????????????????????????Spring??Java EE 6???????????????????????????????? ?????“??”Spring??Java EE 6?????????? ???????? “??”?Spring??Java EE 6?????????????????????????????????? Spring????????????????????????????5?6???????????Spring?????????????????????????????????????????????????????????????????????? ????Spring?????????????????????????????????????????????????????????????????????????????????????????????????????? ???Spring????????????5??10?????????????????????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????·????????????????Java EE 6??????????????1????????????? Java EE 6???????????3????????????????·?????????????????????????????????????????????????????????????Java EE 6???????????????????????? ?????1???????????????Spring????????????????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????????????????? Java EE???????????? ?????????????????????????Java EE?????????????????????????????Java EE??????????Spring?????????????????? ????Java EE?????? ??1????????Java EE?????????????????????Java EE?????????????????????????????????????????????????????????????? Java Developers Workshop 2012 Summer??????Java EE 6???????????? ????GlassFish?????????????????Java EE 6???WAR?????????????????????????????????????????????????????????????·????????????????????100KB?????????????????????????????????????????? Spring??????2????????Java EE???Dependency Injection(DI)??????????????DI??Spring?????????????????????????????Java EE 6???Context Dependency Injection(CDI)???????????DI?????????????Java EE 6????????????????CDI??????????????????? 3?????????????Aspect Oriented Programming(AOP)???????????????????????????????AOP?????????????????????????????????????????????????????????????AOP????????????????????????????????AOP??????????????????????????????????Java EE 6???Interceptor???????Spring AOP??????????????????????????????????????????? 4????????Java EE??????????IDE????????????????????EJB?????????????????????????????????????????Java EE 6?????????????????????????NetBeans?Eclipse?????????????IDE????????????????????????????????????????????????????????????????????????????????????????? ???????Spring?Java EE????????????? ??????????????????Spring??????????????????Java EE 6??????????? ????Java EE???????????(integration testing)?????????????????????Arquillian???????????????????????·????????Arqullian??????????????????????????????????????????????????????????????GlassFish?JBoss???????????·???????????JUnit??????·????????????????????????????? Spring??Java EE?????????5??????? Java EE 6??Spring?????????????????????????????Spring??Java EE 6???????????????????????????????????Spring????????????????????????????? ???????????“????·??·????”????????????????????????????????(????????·??)????????????Java EE 6?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?????1-Spring?????????? ????????????????????Spring?????????????????XML?????????????????????O/R?????·?????????????????????Web????????·???????????????????????? ???????????????????????Spring??????????????????????Spring????????????????????????·???????????????????Spring 3.x??JPA?JSF????Java EE 6??????????????Spring???????????????????????Java EE 6??????????????????????????????????????????? ?????2-Spring?????????????????? ????????????????????????????Spring???????????????????????????????????????????????????Spring???????????????·???????????????????? ????????????????????????????????????“???(??)”???????Web MVC???Kodo??????????????JSF?JPA????????????????????????????????????????????????????????????????????????????????? ?????????????????JSF?????????????Playframework????????????????????????Java EE 6??????????????????????????????????????????????????????????Spring???API??????????????????? ?????3:Spring?????????Java EE 6???????????????? ??????????????????????????Spring??????Java EE????????·??????????????? ????Spring?????????????????????????·???????WAR?????????????????????????????Spring??????????????Spring Beans???????????????????????? ???Java EE??????????????????????????????????????????Java EE 6????????????????·???????CDI????EJB??????????????????????????WAR???????CDI Bean?Session Bean????????????????CDI/EJB????????????????????????????EJB??????Spring?????????????????????? Spring??????Java EE????????·?????????????????????????????????? ???????Spring??????????Java EE???????????WAR??????????????????????????Java EE?????????Spring??????????????????????Java EE??????????? ?????????????????????Spring?Java EE???????????????????????????????????????????????????????????????(???)??????????????????????3????????????????? ????????????Spring?Java EE?????????????? Spring????????????????????????EJB????????CDI??????????????????????????????????????????????????????????CDI????????@Inject????????????????????????? ?????4:Spring??????????? 4??????????????Spring??????????????????????3???????Spring?Java EE??????????? ????3???Java EE 6?????????????Spring???????????????????Java EE 6??????????????????????Java EE 6??????????????????????????????? ?????????Spring JDBC???????????????????????????????????????Spring JDBC????????????????????????????????????? ??????????????·?????????????????????????????????????????????Spring??????????EJB?DAO(Data Access Object)???????????Spring???????????????????????Java EE?????????(???????????????·???????????)? Java EE 6???EJB?JPA??????????????????EJB?????????????????????????JPA????????????????????????Java EE???????????????EJB???????????????????????Java EE 6???EJB????????????????????Spring DAO?Java EE????????????????????????????EJB???????????????Java EE 6?????EJB?????????????????????? Spring?JDBC Templates??????????????“???”?????????O/R????????????????JDBC Templates???????????????????????????????????????O/R???????????????????? ????????????????????JDBC Template??????????????????????????????????????????????????????????????CDI?????????????JDBC Template??????Spring???????????????????????????????????????JDBC Template?Spring????????????????????????????????Template Producer???????CDI??JDBC Template???????????? ?????5:Spring????????? ???????????Spring?????????????????????????????Spring??????????????????Java EE 6?????????????????????pom.xml?????????????????????????????????????????????·????????????WAR????????????????????? ?2????????????? ???Spring??Java EE 6????????????????????????????????????????????????????????????????????????? ????????????????2???????1????????????????????????????????????????????????????????????????????????????????Spring????????????????????????????????????????????????????????????????????????????????????????????????????10????????????????????????????????????????Java EE?????10??????????????·?????????????????????????????????????????? ??????????????????????????????????Spring???????????????????????????????Java EE?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????“?”???????? Spring????????????·????????????????????????????????????JCP???????·?????????????????????????????????????????????????????????????????????????????????????????????????Hibernate?JPA????????????Spring???????????????? ?????????????????????!?Java Developers Workshop 2012 Summer???????????????!! ???Java Developers Workshop 2012 Summer??????????????Oracle Technology Network?????·???? ????????????????????????????????????????????????OTN??????????????? ? ????????? ? Oracle Technology Network?????·???? ???? ?Java Developers Workshop 2012 Summer?– Java EE ?????? – ? ??????????oracle.com???????????????oracle.com????????????????????????????(???????)????????????????????????????????????????????????????????????????????

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• Followup: Python 2.6, 3 abstract base class misunderstanding

  - by Aaron

  I asked a question at Python 2.6, 3 abstract base class misunderstanding. My problem was that python abstract base classes didn't work quite the way I expected them to. There was some discussion in the comments about why I would want to use ABCs at all, and Alex Martelli provided an excellent answer on why my use didn't work and how to accomplish what I wanted. Here I'd like to address why one might want to use ABCs, and show my test code implementation based on Alex's answer. tl;dr: Code after the 16th paragraph. In the discussion on the original post, statements were made along the lines that you don't need ABCs in Python, and that ABCs don't do anything and are therefore not real classes; they're merely interface definitions. An abstract base class is just a tool in your tool box. It's a design tool that's been around for many years, and a programming tool that is explicitly available in many programming languages. It can be implemented manually in languages that don't provide it. An ABC is always a real class, even when it doesn't do anything but define an interface, because specifying the interface is what an ABC does. If that was all an ABC could do, that would be enough reason to have it in your toolbox, but in Python and some other languages they can do more. The basic reason to use an ABC is when you have a number of classes that all do the same thing (have the same interface) but do it differently, and you want to guarantee that that complete interface is implemented in all objects. A user of your classes can rely on the interface being completely implemented in all classes. You can maintain this guarantee manually. Over time you may succeed. Or you might forget something. Before Python had ABCs you could guarantee it semi-manually, by throwing NotImplementedError in all the base class's interface methods; you must implement these methods in derived classes. This is only a partial solution, because you can still instantiate such a base class. A more complete solution is to use ABCs as provided in Python 2.6 and above. Template methods and other wrinkles and patterns are ideas whose implementation can be made easier with full-citizen ABCs. Another idea in the comments was that Python doesn't need ABCs (understood as a class that only defines an interface) because it has multiple inheritance. The implied reference there seems to be Java and its single inheritance. In Java you "get around" single inheritance by inheriting from one or more interfaces. Java uses the word "interface" in two ways. A "Java interface" is a class with method signatures but no implementations. The methods are the interface's "interface" in the more general, non-Java sense of the word. Yes, Python has multiple inheritance, so you don't need Java-like "interfaces" (ABCs) merely to provide sets of interface methods to a class. But that's not the only reason in software development to use ABCs. Most generally, you use an ABC to specify an interface (set of methods) that will likely be implemented differently in different derived classes, yet that all derived classes must have. Additionally, there may be no sensible default implementation for the base class to provide. Finally, even an ABC with almost no interface is still useful. We use something like it when we have multiple except clauses for a try. Many exceptions have exactly the same interface, with only two differences: the exception's string value, and the actual class of the exception. In many exception clauses we use nothing about the exception except its class to decide what to do; catching one type of exception we do one thing, and another except clause catching a different exception does another thing. According to the exception module's doc page, BaseException is not intended to be derived by any user defined exceptions. If ABCs had been a first class Python concept from the beginning, it's easy to imagine BaseException being specified as an ABC. But enough of that. Here's some 2.6 code that demonstrates how to use ABCs, and how to specify a list-like ABC. Examples are run in ipython, which I like much better than the python shell for day to day work; I only wish it was available for python3. Your basic 2.6 ABC: from abc import ABCMeta, abstractmethod class Super(): __metaclass__ = ABCMeta @abstractmethod def method1(self): pass Test it (in ipython, python shell would be similar): In [2]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods method1 Notice the end of the last line, where the TypeError exception tells us that method1 has not been implemented ("abstract methods method1"). That was the method designated as @abstractmethod in the preceding code. Create a subclass that inherits Super, implement method1 in the subclass and you're done. My problem, which caused me to ask the original question, was how to specify an ABC that itself defines a list interface. My naive solution was to make an ABC as above, and in the inheritance parentheses say (list). My assumption was that the class would still be abstract (can't instantiate it), and would be a list. That was wrong; inheriting from list made the class concrete, despite the abstract bits in the class definition. Alex suggested inheriting from collections.MutableSequence, which is abstract (and so doesn't make the class concrete) and list-like. I used collections.Sequence, which is also abstract but has a shorter interface and so was quicker to implement. First, Super derived from Sequence, with nothing extra: from abc import abstractmethod from collections import Sequence class Super(Sequence): pass Test it: In [6]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods __getitem__, __len__ We can't instantiate it. A list-like full-citizen ABC; yea! Again, notice in the last line that TypeError tells us why we can't instantiate it: __getitem__ and __len__ are abstract methods. They come from collections.Sequence. But, I want a bunch of subclasses that all act like immutable lists (which collections.Sequence essentially is), and that have their own implementations of my added interface methods. In particular, I don't want to implement my own list code, Python already did that for me. So first, let's implement the missing Sequence methods, in terms of Python's list type, so that all subclasses act as lists (Sequences). First let's see the signatures of the missing abstract methods: In [12]: help(Sequence.__getitem__) Help on method __getitem__ in module _abcoll: __getitem__(self, index) unbound _abcoll.Sequence method (END) In [14]: help(Sequence.__len__) Help on method __len__ in module _abcoll: __len__(self) unbound _abcoll.Sequence method (END) __getitem__ takes an index, and __len__ takes nothing. And the implementation (so far) is: from abc import abstractmethod from collections import Sequence class Super(Sequence): # Gives us a list member for ABC methods to use. def __init__(self): self._list = [] # Abstract method in Sequence, implemented in terms of list. def __getitem__(self, index): return self._list.__getitem__(index) # Abstract method in Sequence, implemented in terms of list. def __len__(self): return self._list.__len__() # Not required. Makes printing behave like a list. def __repr__(self): return self._list.__repr__() Test it: In [34]: a = Super() In [35]: a Out[35]: [] In [36]: print a [] In [37]: len(a) Out[37]: 0 In [38]: a[0] --------------------------------------------------------------------------- IndexError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() /home/aaron/projects/test/test.py in __getitem__(self, index) 10 # Abstract method in Sequence, implemented in terms of list. 11 def __getitem__(self, index): ---> 12 return self._list.__getitem__(index) 13 14 # Abstract method in Sequence, implemented in terms of list. IndexError: list index out of range Just like a list. It's not abstract (for the moment) because we implemented both of Sequence's abstract methods. Now I want to add my bit of interface, which will be abstract in Super and therefore required to implement in any subclasses. And we'll cut to the chase and add subclasses that inherit from our ABC Super. from abc import abstractmethod from collections import Sequence class Super(Sequence): # Gives us a list member for ABC methods to use. def __init__(self): self._list = [] # Abstract method in Sequence, implemented in terms of list. def __getitem__(self, index): return self._list.__getitem__(index) # Abstract method in Sequence, implemented in terms of list. def __len__(self): return self._list.__len__() # Not required. Makes printing behave like a list. def __repr__(self): return self._list.__repr__() @abstractmethod def method1(): pass class Sub0(Super): pass class Sub1(Super): def __init__(self): self._list = [1, 2, 3] def method1(self): return [x**2 for x in self._list] def method2(self): return [x/2.0 for x in self._list] class Sub2(Super): def __init__(self): self._list = [10, 20, 30, 40] def method1(self): return [x+2 for x in self._list] We've added a new abstract method to Super, method1. This makes Super abstract again. A new class Sub0 which inherits from Super but does not implement method1, so it's also an ABC. Two new classes Sub1 and Sub2, which both inherit from Super. They both implement method1 from Super, so they're not abstract. Both implementations of method1 are different. Sub1 and Sub2 also both initialize themselves differently; in real life they might initialize themselves wildly differently. So you have two subclasses which both "is a" Super (they both implement Super's required interface) although their implementations are different. Also remember that Super, although an ABC, provides four non-abstract methods. So Super provides two things to subclasses: an implementation of collections.Sequence, and an additional abstract interface (the one abstract method) that subclasses must implement. Also, class Sub1 implements an additional method, method2, which is not part of Super's interface. Sub1 "is a" Super, but it also has additional capabilities. Test it: In [52]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods method1 In [53]: a = Sub0() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Sub0 with abstract methods method1 In [54]: a = Sub1() In [55]: a Out[55]: [1, 2, 3] In [56]: b = Sub2() In [57]: b Out[57]: [10, 20, 30, 40] In [58]: print a, b [1, 2, 3] [10, 20, 30, 40] In [59]: a, b Out[59]: ([1, 2, 3], [10, 20, 30, 40]) In [60]: a.method1() Out[60]: [1, 4, 9] In [61]: b.method1() Out[61]: [12, 22, 32, 42] In [62]: a.method2() Out[62]: [0.5, 1.0, 1.5] [63]: a[:2] Out[63]: [1, 2] In [64]: a[0] = 5 --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: 'Sub1' object does not support item assignment Super and Sub0 are abstract and can't be instantiated (lines 52 and 53). Sub1 and Sub2 are concrete and have an immutable Sequence interface (54 through 59). Sub1 and Sub2 are instantiated differently, and their method1 implementations are different (60, 61). Sub1 includes an additional method2, beyond what's required by Super (62). Any concrete Super acts like a list/Sequence (63). A collections.Sequence is immutable (64). Finally, a wart: In [65]: a._list Out[65]: [1, 2, 3] In [66]: a._list = [] In [67]: a Out[67]: [] Super._list is spelled with a single underscore. Double underscore would have protected it from this last bit, but would have broken the implementation of methods in subclasses. Not sure why; I think because double underscore is private, and private means private. So ultimately this whole scheme relies on a gentleman's agreement not to reach in and muck with Super._list directly, as in line 65 above. Would love to know if there's a safer way to do that.

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• [android] How to center buttons on screen horizontally and vertically plus equidistant apart?

  - by marc

  I've been racking my brain (android newbie here, so not hard to do) for awhile trying to figure out how to accomplish this: Desired Layout using a RelativeLayout or something other than AbsoluteLayout which is what this was created with. I'm coming from a Windows programming background where the device adjusts the 'absolute' positioning for you and GUI layout was a non-issue. The first layout works great in the emulator, but doesn't format for my Nexus One or any other screen that differs from the emulator size. I expected this because it's absolutely positioned, but haven't found a solution that will format correctly for different screen sizes. My goal is to have the layout work for different screen sizes and in portrait / landscape. Here's the Code that I'm currently using: [main.xml] <?xml version="1.0" encoding="utf-8"?> <AbsoluteLayout android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" > <Button android:id="@+id/Button01" android:layout_width="188px" android:layout_height="100px" android:text="A" android:layout_y="50px" android:layout_x="65px" android:textSize="48sp"/> <Button android:id="@+id/Button02" android:layout_width="188px" android:layout_height="100px" android:text="B" android:layout_y="175px" android:layout_x="65px" android:textSize="48sp"/> <Button android:id="@+id/Button03" android:layout_width="188px" android:layout_height="100px" android:text="C" android:layout_y="300px" android:layout_x="65px" android:textSize="48sp"/> </AbsoluteLayout> Using tidbits from other questions here, I came up with this, it’s closer, but not there yet. <?xml version="1.0" encoding="utf-8"?> <TableLayout android:gravity="center" android:id="@+id/widget49" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/res/android" > <Button android:id="@+id/Button01" android:layout_width="0dip" android:layout_weight="1" android:text="A" android:textSize="48sp"/> <Button android:id="@+id/Button02" android:layout_width="0dip" android:layout_weight="1" android:text="B" android:textSize="48sp"/> <Button android:id="@+id/Button03" android:layout_width="0dip" android:layout_weight="1" android:text="C" android:textSize="48sp"/> </TableLayout> Here’s a picture of the TableLayout: Another Attempt Any help / guidance would be greatly appreciated.

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• Spring rejecting bean name, no URL paths specified

  - by richever

  I am trying to register an interceptor using a annotation-driven controller configuration. As far as I can tell, I've done everything correctly but when I try testing the interceptor nothing happens. After looking in the logs I found the following: 2010-04-04 20:06:18,231 DEBUG [main] support.AbstractAutowireCapableBeanFactory (AbstractAutowireCapableBeanFactory.java:452) - Finished creating instance of bean 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0' 2010-04-04 20:06:18,515 DEBUG [main] handler.AbstractDetectingUrlHandlerMapping (AbstractDetectingUrlHandlerMapping.java:86) - Rejected bean name 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0': no URL paths identified 2010-04-04 20:06:19,109 DEBUG [main] support.AbstractBeanFactory (AbstractBeanFactory.java:241) - Returning cached instance of singleton bean 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0' Look at the second line of this log snippet. Is Spring rejecting the DefaultAnnotationHandlerMapping bean? And if so could this be the problem with my interceptor not working? Here is my application context: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd" default-autowire="byName"> <!-- Configures the @Controller programming model --> <mvc:annotation-driven /> <!-- Scan for annotations... --> <context:component-scan base-package=" com.splash.web.controller, com.splash.web.service, com.splash.web.authentication"/> <bean id="authorizedUserInterceptor" class="com.splash.web.handler.AuthorizedUserInterceptor"/> <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"> <property name="interceptors"> <list> <ref bean="authorizedUserInterceptor"/> </list> </property> </bean> Here is my interceptor: package com.splash.web.handler; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.log4j.Logger; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.servlet.handler.HandlerInterceptorAdapter; public class AuthorizedUserInterceptor extends HandlerInterceptorAdapter { @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { log.debug(">>> Operation intercepted..."); return true; } } Does anyone see anything wrong with this? What does the error I mentioned above actually mean and could it have any bearing on the interceptor not being called? Thanks!

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• ActiveDirectoryMembershipProvider and ADAM (or AD LDS) and SetPassword

  - by Iulian

  By the subject line it seems to be a rather broad subject and I need some help here. Basically what I want is to use ActiveDirectoryMembershipProvider with an ADAM instance to authenticate users in an ASP.NET web application. My development environment is a windows 7 machine with an AD LDS instance on it whilst the QA server is a Windows 2003 server with an ADAM instance on it. I have all the required users on both instances plus one with adminsitrator role (CN=Admin,CN=xxx,DC=xxx,C=xx) which I want to use as the connection user. Using connectonProtecton="None" connectionUsername="CN=Admin,CN=xxx,DC=xxx,C=xx" connectionPassword="xxx" I am able to authenticate on both environments (dev & qa). If I change to the connectionProtection to "Secure" I am not able to authenticate anymore; the error I get is "Parser Error Message: Unable to establish secure connection with the server" To me it sounds wrong to use connectionProtection="None" although I found on the net a lot of samples using this setting. Can I use connectionProtection="Secure" to connect to an ADAM instance using an account defined on that instance having Administrator role? What other choices do I have (like using an domain account)? What if my machine where I am to deploy the application is not a part of the domain, will this affect in any way the behavior? I am novice in the respect so I would really appreciate some clear answers or some directions as where to look? Now beside the "signing in" feature of the ActiveDirectoryMembershipProvider I also want to add an extra one, which is setting the password without knowing the old one (something that will be used by a "reset password" feature). So I added a couple of extension methods to the provider, and used System.DirectoryServices classes like DirectoryEntry and the like. When creating a directory entry I use the same credentials provided in web.config for the provider minus the AuthenticationType as I don't know what is right combination of the flags that corresponds to None/Secure. I am able to use Invoke "SetPassword" with ADS_OPTION_PASSWORD_METHOD option as ADS_PASSWORD_ENCODE_CLEAR on my dev machine (w/ AD LDS instance); nevertheless on qa environment (w/ ADAM instance) I am getting an error like "Exception Details: System.DirectoryServices.DirectoryServicesCOMException: An operations error occurred. (Exception from HRESULT: 0x80072020)" I am quite sure it is not about AD LDS vs ADAM but probably another configuration / permission issue. So can anyone help me with some hints on how to use this SetPassword feature? And as a general question what are the best practices when it comes to using ADAM regarding security, programming etc? Thanks in advance Iulian

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• C# and WUAPI: BeginDownload function

  - by Laurus Schluep

  first things first: I have no experience in object-oriented programming, whatsoever. I created my share of VB scripts and a bit of Java in school, but that's it. So my problem most likely lies there. But nevertheless, for the past few days, I've been trying to get a little application together that allows me to scan for, select and install Windows updates. So far I've been able to understand most of the reference and with the help of a few posts around the internet and I'm now at the point where I can select and download updates. So far I've been able to download a collection of updates using the following code: UpdateCollection CurrentInstallCollection = (UpdateCollection)e.Argument; UpdateDownloader CurrentDownloader = CurrentSession.CreateUpdateDownloader(); CurrentDownloader.Updates = CurrentInstallCollection; This is run in a background worker and returns once the download is done. It works just fine, I can see the updates getting downloaded on the file system but there isn't really a way to display the progress within the application. To do such a thing, there is the IDownloadJob interface that allows me to use the .BeginDownload method of the downloader (UpdateSession.CreateUpdateDownloader)...i think, at least. :D And here comes the problem: I have now tried for about 6 hours to get the code working, but no matter what I tried nothing worked. Also, there isn't much information around on the internet about the .BeginDownload method (or at least it seems that way), but my call of the method doesn't work: IDownloadJob CurrentDownloadJob = CurrentDownloader.BeginDownload(); I have no clue what arguments to supply...I've tried methods, objects...to no avail. The complete block of code looks like this: UpdateCollection CurrentInstallCollection = (UpdateCollection)e.Argument; UpdateDownloader CurrentDownloader = CurrentSession.CreateUpdateDownloader(); CurrentDownloader.Updates = CurrentInstallCollection; IDownloadJob CurrentDownloadJob = CurrentDownloader.BeginDownload(); IDownloadProgress CurrentJobProgess = CurrentDownloadJob.GetProgress(); tbStatus.Text = Convert.ToString(CurrentJobProgess.PercentComplete); I've found one source on the internet that called the method with .BeginDownload(this,this,this), which does not report any error in the code editor but probably won't help with reporting as it is my understanding, that the arguments supplied are the methods that are called when the described event occurrs (progress has changed or the download has finished). I also tried this, but it didn't work either: http://social.msdn.microsoft.com/Forums/en/csharpgeneral/thread/636a8399-2bc1-46ff-94df-a58cebfe688c A detailed description of the BeginDownload method: http://msdn.microsoft.com/en-us/library/aa386132(v=VS.85).aspx WUAPI Reference: Unfortunately I'm not allowed to post the link, but the link to the BeginDownload method goes to the same place. :) I know, it's quite a bit to ask, but if someone could point me in the right direction (as in which arguments to pass and how), it'd be very much appreciated! :)

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• Long-running ASP.NET tasks

  - by John Leidegren

  I know there's a bunch of APIs out there that do this, but I also know that the hosting environment (being ASP.NET) puts restrictions on what you can reliably do in a separate thread. I could be completely wrong, so please correct me if I am, this is however what I think I know. A request typically timeouts after 120 seconds (this is configurable) but eventually the ASP.NET runtime will kill a request that's taking too long to complete. The hosting environment, typically IIS, employs process recycling and can at any point decide to recycle your app. When this happens all threads are aborted and the app restarts. I'm however not sure how aggressive it is, it would be kind of stupid to assume that it would abort a normal ongoing HTTP request but I would expect it to abort a thread because it doesn't know anything about the unit of work of a thread. If you had to create a programming model that easily and reliably and theoretically put a long running task, that would have to run for days, how would you accomplish this from within an ASP.NET application? The following are my thoughts on the issue: I've been thinking a long the line of hosting a WCF service in a win32 service. And talk to the service through WCF. This is however not very practical, because the only reason I would choose to do so, is to send tasks (units of work) from several different web apps. I'd then eventually ask the service for status updates and act accordingly. My biggest concern with this is that it would NOT be a particular great experience if I had to deploy every task to the service for it to be able to execute some instructions. There's also this issue of input, how would I feed this service with data if I had a large data set and needed to chew through it? What I typically do right now is this SELECT TOP 10 * FROM WorkItem WITH (ROWLOCK, UPDLOCK, READPAST) WHERE WorkCompleted IS NULL It allows me to use a SQL Server database as a work queue and periodically poll the database with this query for work. If the work item completed with success, I mark it as done and proceed until there's nothing more to do. What I don't like is that I could theoretically be interrupted at any point and if I'm in-between success and marking it as done, I could end up processing the same work item twice. I might be a bit paranoid and this might be all fine but as I understand it there's no guarantee that that won't happen... I know there's been similar questions on SO before but non really answers with a definitive answer. This is a really common thing, yet the ASP.NET hosting environment is ill equipped to handle long-running work. Please share your thoughts.

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• Why 32-bit color EGL configurations fail with EGL_BAD_MATCH on Moto Droid?

  - by Gilead

  I'm trying to figure out why certain EGL configurations cause eglMakeCurrent() call to return EGL_BAD_MATCH on Motorola Droid running Android 2.1u1. This is a full list of hardware-accelerated EGL configurations (those with EGL_CONFIG_CAVEAT == EGL_NONE) as there's a few others with EGL_CONFIG_CAVEAT == EGL_SLOW_CONFIG but those are backed by PixelFlinger 1.2 meaning they're using software renderer. ID: 0 RGB: 8, 8, 8 Alpha: 8 Depth: 24 Stencil: 8 // BAD MATCH ID: 1 RGB: 8, 8, 8 Alpha: 8 Depth: 0 Stencil: 0 // BAD MATCH ID: 2 RGB: 8, 8, 8 Alpha: 8 Depth: 24 Stencil: 8 // BAD MATCH ID: 3 RGB: 8, 8, 8 Alpha: 8 Depth: 24 Stencil: 8 // BAD MATCH ID: 4 RGB: 8, 8, 8 Alpha: 8 Depth: 0 Stencil: 0 // BAD MATCH ID: 5 RGB: 8, 8, 8 Alpha: 8 Depth: 24 Stencil: 8 // BAD MATCH ID: 6 RGB: 5, 6, 5 Alpha: 0 Depth: 24 Stencil: 8 ID: 7 RGB: 5, 6, 5 Alpha: 0 Depth: 0 Stencil: 0 ID: 8 RGB: 5, 6, 5 Alpha: 0 Depth: 24 Stencil: 8 Clearly, all configurations with 32-bit color depth fail and all 16-bit ones are OK but: 1. Why? 2. WHY?! :) 3. How do I tell which ones would fail before actually trying to use them? The code below is as simple as it can get. I put if (v[0] == 6) there to check different configs, normally they're chosen by half-clever config matcher :) private void createSurface(SurfaceHolder holder) { egl = (EGL10)EGLContext.getEGL(); eglDisplay = egl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY); egl.eglInitialize(eglDisplay, null); int[] numConfigs = new int[1]; egl.eglChooseConfig(eglDisplay, new int[] { EGL10.EGL_NONE }, null, 0, numConfigs); EGLConfig[] configs = new EGLConfig[numConfigs[0]]; egl.eglChooseConfig(eglDisplay, new int[] { EGL10.EGL_NONE }, configs, numConfigs[0], numConfigs); int[] v = new int[1]; for (EGLConfig c : configs) { egl.eglGetConfigAttrib(eglDisplay, c, EGL10.EGL_CONFIG_ID, v); if (v[0] == 6) { eglConfig = c; } } eglContext = egl.eglCreateContext(eglDisplay, eglConfig, EGL10.EGL_NO_CONTEXT, null); if (eglContext == null || eglContext == EGL10.EGL_NO_CONTEXT) { throw new RuntimeException("Unable to create EGL context"); } eglSurface = egl.eglCreateWindowSurface(eglDisplay, eglConfig, holder, null); if (eglSurface == null || eglSurface == EGL10.EGL_NO_SURFACE) { throw new RuntimeException("Unable to create EGL surface"); } if (!egl.eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext)) { throw new RuntimeException("Unable to make EGL current"); } gl = (GL10)eglContext.getGL(); }

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