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  • Find only physical network adapters with WMI Win32_NetworkAdapter class

    - by Mladen Prajdic
    WMI is Windows Management Instrumentation infrastructure for managing data and machines. We can access it by using WQL (WMI querying language or SQL for WMI). One thing to remember from the WQL link is that it doesn't support ORDER BY. This means that when you do SELECT * FROM wmiObject, the returned order of the objects is not guaranteed. It can return adapters in different order based on logged-in user, permissions of that user, etc… This is not documented anywhere that I've looked and is derived just from my observations. To get network adapters we have to query the Win32_NetworkAdapter class. This returns us all network adapters that windows detect, real and virtual ones, however it only supplies IPv4 data. I've tried various methods of combining properties that are common on all systems since Windows XP. The first thing to do to remove all virtual adapters (like tunneling, WAN miniports, etc…) created by Microsoft. We do this by adding WHERE Manufacturer!='Microsoft' to our WMI query. This greatly narrows the number of adapters we have to work with. Just on my machine it went from 20 adapters to 5. What was left were one real physical Realtek LAN adapter, 2 virtual adapters installed by VMware and 2 virtual adapters installed by VirtualBox. If you read the Win32_NetworkAdapter help page you'd notice that there's an AdapterType that enumerates various adapter types like LAN or Wireless and AdapterTypeID that gives you the same information as AdapterType only in integer form. The dirty little secret is that these 2 properties don't work. They are both hardcoded, AdapterTypeID to "0" and AdapterType to "Ethernet 802.3". The only exceptions I've seen so far are adapters that have no values at all for the two properties, "RAS Async Adapter" that has values of AdapterType = "Wide Area Network" and AdapterTypeID = "3" and various tunneling adapters that have values of AdapterType = "Tunnel" and AdapterTypeID = "15". In the help docs there isn't even a value for 15. So this property was of no help. Next property to give hope is NetConnectionId. This is the name of the network connection as it appears in the Control Panel -> Network Connections. Problem is this value is also localized into various languages and can have different names for different connection. So both of these properties don't help and we haven't even started talking about eliminating virtual adapters. Same as the previous one this property was also of no help. Next two properties I checked were ConfigManagerErrorCode and NetConnectionStatus in hopes of finding disabled and disconnected adapters. If an adapter is enabled but disconnected the ConfigManagerErrorCode = 0 with different NetConnectionStatus. If the adapter is disabled it reports ConfigManagerErrorCode = 22. This looked like a win by using (ConfigManagerErrorCode=0 or ConfigManagerErrorCode=22) in our condition. This way we get enabled (connected and disconnected adapters). Problem with all of the above properties is that none of them filter out the virtual adapters installed by virtualization software like VMware and VirtualBox. The last property to give hope is PNPDeviceID. There's an interesting observation about physical and virtual adapters with this property. Every virtual adapter PNPDeviceID starts with "ROOT\". Even VMware and VirtualBox ones. There were some really, really old physical adapters that had PNPDeviceID starting with "ROOT\" but those were in pre win XP era AFAIK. Since my minimum system to check was Windows XP SP2 I didn't have to worry about those. The only virtual adapter I've seen to not have PNPDeviceID start with "ROOT\" is the RAS Async Adapter for Wide Area Network. But because it is made by Microsoft we've eliminated it with the first condition for the manufacturer. Using the PNPDeviceID has so far proven to be really effective and I've tested it on over 20 different computers of various configurations from Windows XP laptops with wireless and bluetooth cards to virtualized Windows 2008 R2 servers. So far it always worked as expected. I will appreciate you letting me know if you find a configuration where it doesn't work. Let's see some C# code how to do this: ManagementObjectSearcher mos = null;// WHERE Manufacturer!='Microsoft' removes all of the // Microsoft provided virtual adapters like tunneling, miniports, and Wide Area Network adapters.mos = new ManagementObjectSearcher(@"SELECT * FROM Win32_NetworkAdapter WHERE Manufacturer != 'Microsoft'");// Trying the ConfigManagerErrorCode and NetConnectionStatus variations // proved to still not be enough and it returns adapters installed by // the virtualization software like VMWare and VirtualBox// ConfigManagerErrorCode = 0 -> Device is working properly. This covers enabled and/or disconnected devices// ConfigManagerErrorCode = 22 AND NetConnectionStatus = 0 -> Device is disabled and Disconnected. // Some virtual devices report ConfigManagerErrorCode = 22 (disabled) and some other NetConnectionStatus than 0mos = new ManagementObjectSearcher(@"SELECT * FROM Win32_NetworkAdapter WHERE Manufacturer != 'Microsoft' AND (ConfigManagerErrorCode = 0 OR (ConfigManagerErrorCode = 22 AND NetConnectionStatus = 0))");// Final solution with filtering on the Manufacturer and PNPDeviceID not starting with "ROOT\"// Physical devices have PNPDeviceID starting with "PCI\" or something else besides "ROOT\"mos = new ManagementObjectSearcher(@"SELECT * FROM Win32_NetworkAdapter WHERE Manufacturer != 'Microsoft' AND NOT PNPDeviceID LIKE 'ROOT\\%'");// Get the physical adapters and sort them by their index. // This is needed because they're not sorted by defaultIList<ManagementObject> managementObjectList = mos.Get() .Cast<ManagementObject>() .OrderBy(p => Convert.ToUInt32(p.Properties["Index"].Value)) .ToList();// Let's just show all the properties for all physical adapters.foreach (ManagementObject mo in managementObjectList){ foreach (PropertyData pd in mo.Properties) Console.WriteLine(pd.Name + ": " + (pd.Value ?? "N/A"));}   That's it. Hope this helps you in some way.

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  • Big Data – Evolution of Big Data – Day 3 of 21

    - by Pinal Dave
    In yesterday’s blog post we answered what is the Big Data. Today we will understand why and how the evolution of Big Data has happened. Though the answer is very simple, I would like to tell it in the form of a history lesson. Data in Flat File In earlier days data was stored in the flat file and there was no structure in the flat file.  If any data has to be retrieved from the flat file it was a project by itself. There was no possibility of retrieving the data efficiently and data integrity has been just a term discussed without any modeling or structure around. Database residing in the flat file had more issues than we would like to discuss in today’s world. It was more like a nightmare when there was any data processing involved in the application. Though, applications developed at that time were also not that advanced the need of the data was always there and there was always need of proper data management. Edgar F Codd and 12 Rules Edgar Frank Codd was a British computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases. He presented 12 rules for the Relational Database and suddenly the chaotic world of the database seems to see discipline in the rules. Relational Database was a promising land for all the unstructured database users. Relational Database brought into the relationship between data as well improved the performance of the data retrieval. Database world had immediately seen a major transformation and every single vendors and database users suddenly started to adopt the relational database models. Relational Database Management Systems Since Edgar F Codd proposed 12 rules for the RBDMS there were many different vendors who started them to build applications and tools to support the relationship between database. This was indeed a learning curve for many of the developer who had never worked before with the modeling of the database. However, as time passed by pretty much everybody accepted the relationship of the database and started to evolve product which performs its best with the boundaries of the RDBMS concepts. This was the best era for the databases and it gave the world extreme experts as well as some of the best products. The Entity Relationship model was also evolved at the same time. In software engineering, an Entity–relationship model (ER model) is a data model for describing a database in an abstract way. Enormous Data Growth Well, everything was going fine with the RDBMS in the database world. As there were no major challenges the adoption of the RDBMS applications and tools was pretty much universal. There was a race at times to make the developer’s life much easier with the RDBMS management tools. Due to the extreme popularity and easy to use system pretty much every data was stored in the RDBMS system. New age applications were built and social media took the world by the storm. Every organizations was feeling pressure to provide the best experience for their users based the data they had with them. While this was all going on at the same time data was growing pretty much every organization and application. Data Warehousing The enormous data growth now presented a big challenge for the organizations who wanted to build intelligent systems based on the data and provide near real time superior user experience to their customers. Various organizations immediately start building data warehousing solutions where the data was stored and processed. The trend of the business intelligence becomes the need of everyday. Data was received from the transaction system and overnight was processed to build intelligent reports from it. Though this is a great solution it has its own set of challenges. The relational database model and data warehousing concepts are all built with keeping traditional relational database modeling in the mind and it still has many challenges when unstructured data was present. Interesting Challenge Every organization had expertise to manage structured data but the world had already changed to unstructured data. There was intelligence in the videos, photos, SMS, text, social media messages and various other data sources. All of these needed to now bring to a single platform and build a uniform system which does what businesses need. The way we do business has also been changed. There was a time when user only got the features what technology supported, however, now users ask for the feature and technology is built to support the same. The need of the real time intelligence from the fast paced data flow is now becoming a necessity. Large amount (Volume) of difference (Variety) of high speed data (Velocity) is the properties of the data. The traditional database system has limits to resolve the challenges this new kind of the data presents. Hence the need of the Big Data Science. We need innovation in how we handle and manage data. We need creative ways to capture data and present to users. Big Data is Reality! Tomorrow In tomorrow’s blog post we will try to answer discuss Basics of Big Data Architecture. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Xamarin Designer for Android Webinar - Recording

    - by Wallym
    Here is some info on the recording of the webinar that I did last week for AppDev regarding the Xamarin Designer for Android.Basic Info: Android user interfaces can be created declaratively by using XML files, or programmatically in code. The Xamarin Android Designer allows developers to create and modify declarative layouts visually, without having to deal with the tedium of hand-editing XML files. The designer also provides real-time feedback, which lets the developer validate changes without having to redeploy the application in order to test a design. This can speed up UI development in Android tremendously. In this webinar, we'll take a look at UI Design in Mono for Android, the basics of the Xamarin Android Designer, and build a simple application with the designer.Here is the link:http://media.appdev.com/EDGE/LL/livelearn05232012.wmvI think it will only play in Internet Explorer.  Enjoy!

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  • CLR via C# 3rd Edition is out

    - by Abhijeet Patel
    Time for some book news update. CLR via C#, 3rd Edition seems to have been out for a little while now. The book was released in early Feb this year, and needless to say my copy is on it’s way. I can barely wait to dig in and chew on the goodies that one of the best technical authors and software professionals I respect has in store. The 2nd edition of the book was an absolute treat and this edition promises to be no less. Here is a brief description of what’s new and updated from the 2nd edition. Part I – CLR Basics Chapter 1-The CLR’s Execution Model Added about discussion about C#’s /optimize and /debug switches and how they relate to each other. Chapter 2-Building, Packaging, Deploying, and Administering Applications and Types Improved discussion about Win32 manifest information and version resource information. Chapter 3-Shared Assemblies and Strongly Named Assemblies Added discussion of TypeForwardedToAttribute and TypeForwardedFromAttribute. Part II – Designing Types Chapter 4-Type Fundamentals No new topics. Chapter 5-Primitive, Reference, and Value Types Enhanced discussion of checked and unchecked code and added discussion of new BigInteger type. Also added discussion of C# 4.0’s dynamic primitive type. Chapter 6-Type and Member Basics No new topics. Chapter 7-Constants and Fields No new topics. Chapter 8-Methods Added discussion of extension methods and partial methods. Chapter 9-Parameters Added discussion of optional/named parameters and implicitly-typed local variables. Chapter 10-Properties Added discussion of automatically-implemented properties, properties and the Visual Studio debugger, object and collection initializers, anonymous types, the System.Tuple type and the ExpandoObject type. Chapter 11-Events Added discussion of events and thread-safety as well as showing a cool extension method to simplify the raising of an event. Chapter 12-Generics Added discussion of delegate and interface generic type argument variance. Chapter 13-Interfaces No new topics. Part III – Essential Types Chapter 14-Chars, Strings, and Working with Text No new topics. Chapter 15-Enums Added coverage of new Enum and Type methods to access enumerated type instances. Chapter 16-Arrays Added new section on initializing array elements. Chapter 17-Delegates Added discussion of using generic delegates to avoid defining new delegate types. Also added discussion of lambda expressions. Chapter 18-Attributes No new topics. Chapter 19-Nullable Value Types Added discussion on performance. Part IV – CLR Facilities Chapter 20-Exception Handling and State Management This chapter has been completely rewritten. It is now about exception handling and state management. It includes discussions of code contracts and constrained execution regions (CERs). It also includes a new section on trade-offs between writing productive code and reliable code. Chapter 21-Automatic Memory Management Added discussion of C#’s fixed state and how it works to pin objects in the heap. Rewrote the code for weak delegates so you can use them with any class that exposes an event (the class doesn’t have to support weak delegates itself). Added discussion on the new ConditionalWeakTable class, GC Collection modes, Full GC notifications, garbage collection modes and latency modes. I also include a new sample showing how your application can receive notifications whenever Generation 0 or 2 collections occur. Chapter 22-CLR Hosting and AppDomains Added discussion of side-by-side support allowing multiple CLRs to be loaded in a single process. Added section on the performance of using MarshalByRefObject-derived types. Substantially rewrote the section on cross-AppDomain communication. Added section on AppDomain Monitoring and first chance exception notifications. Updated the section on the AppDomainManager class. Chapter 23-Assembly Loading and Reflection Added section on how to deploy a single file with dependent assemblies embedded inside it. Added section comparing reflection invoke vs bind/invoke vs bind/create delegate/invoke vs C#’s dynamic type. Chapter 24-Runtime Serialization This is a whole new chapter that was not in the 2nd Edition. Part V – Threading Chapter 25-Threading Basics Whole new chapter motivating why Windows supports threads, thread overhead, CPU trends, NUMA Architectures, the relationship between CLR threads and Windows threads, the Thread class, reasons to use threads, thread scheduling and priorities, foreground thread vs background threads. Chapter 26-Performing Compute-Bound Asynchronous Operations Whole new chapter explaining the CLR’s thread pool. This chapter covers all the new .NET 4.0 constructs including cooperative cancelation, Tasks, the aralle class, parallel language integrated query, timers, how the thread pool manages its threads, cache lines and false sharing. Chapter 27-Performing I/O-Bound Asynchronous Operations Whole new chapter explaining how Windows performs synchronous and asynchronous I/O operations. Then, I go into the CLR’s Asynchronous Programming Model, my AsyncEnumerator class, the APM and exceptions, Applications and their threading models, implementing a service asynchronously, the APM and Compute-bound operations, APM considerations, I/O request priorities, converting the APM to a Task, the event-based Asynchronous Pattern, programming model soup. Chapter 28-Primitive Thread Synchronization Constructs Whole new chapter discusses class libraries and thread safety, primitive user-mode, kernel-mode constructs, and data alignment. Chapter 29-Hybrid Thread Synchronization Constructs Whole new chapter discussion various hybrid constructs such as ManualResetEventSlim, SemaphoreSlim, CountdownEvent, Barrier, ReaderWriterLock(Slim), OneManyResourceLock, Monitor, 3 ways to solve the double-check locking technique, .NET 4.0’s Lazy and LazyInitializer classes, the condition variable pattern, .NET 4.0’s concurrent collection classes, the ReaderWriterGate and SyncGate classes.

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  • Computer Science or Computer Engineering for Data Science and Machine Learning

    - by ATMathew
    I'm a 25 year old data consultant who is considering returning to school to get a second bachelors degree in computer science or engineering. My interest is data science and machine learning. I use programming as a means to an end, and use languages like Python, R, C, Java, and Hadoop to find meaning in large data sets. Would a computer science or computer engineering degree be better for this? I realize that a statistics degree may be even more beneficial, but I'll be at a school which dosn't have a stats department or a computational math department.

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  • how should I network my turn based game?

    - by ddriver1
    I'm writing a very basic turn based strategy game which allows a player to select units and attack enemy units on their turn. The game is written in Java using the slick2d library and I plan to use kyronet for the networking api. I want the game to be networked, but I do not know how I should go about it. My current idea is to connect two users together, and the first one to join the game becomes the game host, while the other becomes the client. However after reading http://gafferongames.com/networking-for-game-programmers/what-every-programmer-needs-to-know-about-game-networking/ it seems my game would be suited to a peer to peer lockstep model. Would that make programming the networking side much easier? Any suggestions on how I should structure my networking would be greatly appreciated

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  • Prevent service from starting

    - by Evan Plaice
    So, I do Arduino development on my system to program arduinos using the FTDI USB programming interface (if you have no idea what this means don't worry). The issue arises because the FTDI interface uses tty to communicate and it conflicts with one of the default ubuntu services. The default service in question is called brltty (which enables braille accessibility for people with impaired vision). Considering that I don't have any particular use for this service and it's annoying to stop it manually (using 'service brltty stop') after I restart my system... Where would I configure this (or any) service to prevent it from loading on startup? Note: I also have this issue with qemu-kvm conflicting with virtualbox.

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  • Can and should UDF be used as a hard drive format?

    - by dlamblin
    Several time recently I've seen UDF suggested as the solution to a cross platform format for a drive used on Linux, Mac OS X and Windows XP and above. I've searched here and not found the same suggestion (most are suggesting ntfs-3g which seems to cost money and isn't preinstalled on a Mac). So my question is: how is this done right, and has anyone done this? Have you then filled up the drive and deleted some files to make space finding that everything works like a real r/w format even though it seems to have been primarily a write once format?

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  • 2012 Oracle Fusion Innovation Awards - Part 2

    - by Michelle Kimihira
    Author: Moazzam Chaudry Continuing from Friday's blog on 2012 Oracle Fusion Innovation Awards, this blog (Part 2) will provide more details around the customers. It was a tremendous honor to be in single room of winners. We only wish we could have had more time to share stories from all the winners.  We received great insight from all the innovative solutions that our customers deploy and would like to share them broadly, so that others can benefit from best practices. There was a customer panel session joined by Ingersoll Rand, Nike and Motability and here is what was discussed: Barry Bonar, Enterprise Architect from Ingersoll Rand shared details around their solution, comprised of Oracle Exalogic, Oracle WebLogic Server and Oracle SOA Suite. This combined solutoin enabled their business transformation to increase decision-making, speed and efficiency, resulting in 40% reduced IT spend, 41X Faster response time and huge cost savings. Ashok Balakrishnan, Architect from Nike shared how they leveraged Oracle Coherence to analyze their digital "footprint" of activities. This helps them compete, collaborate and compare athletic data over time. Lastly, Ashley Doodly, Head of IT from Motability shared details around their solution compromised of Oracle SOA Suite, Service Bus, ADF, Coherence, BO and E-Business Suite. This solution helped Motability achieve 100% ROI within the first few months, performance in seconds vs. 10's of minutes and tremendous improvement in throughput that increased up to 50%.  This year's winners by category are: Oracle Exalogic Customer Results using Fusion Middleware Netshoes ATG on Exalogic: 6X Reduced H/W foot print, 6.2X increased throughput and 3 weeks time to market Claro Part of America Movil, running mission critical Java Application on Exalogic with 35X Faster Java response time, 5X Throughput Underwriters Laboratories Exalogic as an Apps Consolidation platform to power tremendous growth Ingersoll Rand EBS on Exalogic: Up to 40% Reduction in overall IT budget, 3x reduced foot print Oracle Cloud Application Foundation Customer Results using Fusion Middleware  Mazda Motor Corporation Tuxedo ART Batch runtime environment to migrate their batch apps on new open environment and reduce main frame cost. HOTELBEDS Technology Open Source to WebLogic transformation Globalia Corporation Introduced Oracle Coherence to fully reengineer DTH system and provide multiple business and technical benefits Nike Nike+, digital sports platform, has 8M users and is expecting an 5X increase in users, many of who will carry multiple devices that frequently sync data with the Digital Sport platform Comcast Corporation The solution is expected to increase availability, continuity, performance, and simplify and make the code at the application layer more flexible. Oracle SOA and Oracle BPM Customer Results using Fusion Middleware NTT Docomo Network traffic solution based on Oracle event processing and coherence - massive in scale: 12M users (50M in future) - 800,000 events/sec. Schneider National, Inc. SOA/B2B/ADF/Data Integration to orchestrate key order processes across Siebel, OTM & EBS.  Platform runs 60M trans/day and  50 million composite SOA instances per day across 10G and 11G Amadeus Oracle BPM solution: Business Rules and processes vary across local (80), regional (~10) and corporate approval process. Up to 10 levels of approval. Plans to deploy across 20+ markets Navitar SOA solution integrates a fully non-Oracle legacy application/ERP environment using Oracle’s SOA Suite and Oracle AIA Foundation Pack. Motability Uses SOA Suite to synchronize data across the systems and to manage the vehicle remarketing process Oracle WebCenter Customer Results using Fusion Middleware  News Limited Single platform running websites for 50% of Australia's newspapers University of Louisville “Facebook for Medicine”: Oracle Webcenter platform and Oracle BIEE to analyze patient test data and uncover potential health issues. Expecting annualized ROI of 277% China Mobile Jiangsu Company portal (25k users) to drive collaboration & productivity Life Technologies Portal for remotely monitoring & repairing biotech instruments LA Dept. of Water & Power Oracle WebCenter Portal to power ladwp.com on desktop and mobile for 1.6million users Oracle Identity Management Customer Results using Fusion Middleware Education Testing Service Identity Management platform for provisioning & SSO of 6 million GRE, GMAT, TOEFL customers Avea Oracle Identity Manager allowing call center personnel to quickly change Identity Profile to handle varying call loads based on a user self service interface. Decreased Admin Cost by 30% Oracle Data Integration Customer Results using Fusion Middleware Raymond James Near real-time integration for improved systems (throughput & performance) and enhanced operational flexibility in a 24 X 7 environment Wm Morrison Supermarkets Electronic Point of Sale integration handling over 80 million transactions a day in near real time (15 min intervals) Oracle Application Development Framework and Oracle Fusion Development Customer Results using Fusion Middleware Qualcomm Incorporated Solution providing  immediate business value enabling a self-service model necessary for growing the new customer base, an increase in customer satisfaction, reduced “time-to-deliver” Micros Systems, Inc. ADF, SOA Suite, WebCenter  enables services that include managing distribution of hotel rooms availability and rates to channels such as Hotel Web-site, Expedia, etc. Marfin Egnatia Bank A new web 2.0 UI provides a much richer experience through the ADF solution with the end result being one of boosting end-user productivity    Business Analytics (Oracle BI, Oracle EPM, Oracle Exalytics) Customer Results using Fusion Middleware INC Research Self-service customer portal delivering 5–10% of the overall revenue - expected to grow fast with the BI solution Experian Reduction in Time to Complete the Financial Close Process Hologic Inc Solution, saving months of decision-making uncertainty! We look forward to seeing many more innovative nominations. The nominatation process for 2013 begins in April 2013.    Additional Information: Blog: Oracle WebCenter Award Winners Blog: Oracle Identity Management Winners Blog: Oracle Exalogic Winners Blog: SOA, BPM and Data Integration will be will feature award winners in its respective areas this week Subscribe to our regular Fusion Middleware Newsletter Follow us on Twitter and Facebook

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  • Text editor with coloring to highlight "non-parameters" in conf files?

    - by Zabba
    Some .conf files have a lot of comments and parameters in them like so: # WINS Server - Tells the NMBD components of Samba to be a WINS Client # Note: Samba can be either a WINS Server, or a WINS Client, but NOT both ; wins server = w.x.y.z # This will prevent nmbd to search for NetBIOS names through DNS. dns proxy = no ..... It gets difficult to look for only the parameters among the plethora of comments, so, is there some text editor that can highlight the comments in dark grey so that the real parameters stand out?

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  • LightFish, Adam Bien's lightweight telemetry application

    - by alexismp
    Adam Bien (Java Champion, JavaEE expert, book author, etc...), has been a GlassFish enthusiast for a while and he proves it again with his new open source project - LightFish, a lightweight monitoring and visualization application for GlassFish. Adam has a short intro and screencast about this standalone WAR application. The tool uses the new JavaEE 6 self-described JDBC connection and the GlassFish-bundled Derby database to provide drag-and-drop install. At runtime, once monitoring is enabled, calls to the RESTful admin API for GlassFish are emitted from a JavaFX dashboard plotting in real-time telemetry data on charts and graphs, including data for "Paranormal Activity". Check it out!

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  • Liskov Substitution Principle and the Oft Forgot Third Wheel

    - by Stacy Vicknair
    Liskov Substitution Principle (LSP) is a principle of object oriented programming that many might be familiar with from the SOLID principles mnemonic from Uncle Bob Martin. The principle highlights the relationship between a type and its subtypes, and, according to Wikipedia, is defined by Barbara Liskov and Jeanette Wing as the following principle:   Let be a property provable about objects of type . Then should be provable for objects of type where is a subtype of .   Rectangles gonna rectangulate The iconic example of this principle is illustrated with the relationship between a rectangle and a square. Let’s say we have a class named Rectangle that had a property to set width and a property to set its height. 1: Public Class Rectangle 2: Overridable Property Width As Integer 3: Overridable Property Height As Integer 4: End Class   We all at some point here that inheritance mocks an “IS A” relationship, and by gosh we all know square IS A rectangle. So let’s make a square class that inherits from rectangle. However, squares do maintain the same length on every side, so let’s override and add that behavior. 1: Public Class Square 2: Inherits Rectangle 3:  4: Private _sideLength As Integer 5:  6: Public Overrides Property Width As Integer 7: Get 8: Return _sideLength 9: End Get 10: Set(value As Integer) 11: _sideLength = value 12: End Set 13: End Property 14:  15: Public Overrides Property Height As Integer 16: Get 17: Return _sideLength 18: End Get 19: Set(value As Integer) 20: _sideLength = value 21: End Set 22: End Property 23: End Class   Now, say we had the following test: 1: Public Sub SetHeight_DoesNotAffectWidth(rectangle As Rectangle) 2: 'arrange 3: Dim expectedWidth = 4 4: rectangle.Width = 4 5:  6: 'act 7: rectangle.Height = 7 8:  9: 'assert 10: Assert.AreEqual(expectedWidth, rectangle.Width) 11: End Sub   If we pass in a rectangle, this test passes just fine. What if we pass in a square?   This is where we see the violation of Liskov’s Principle! A square might "IS A” to a rectangle, but we have differing expectations on how a rectangle should function than how a square should! Great expectations Here’s where we pat ourselves on the back and take a victory lap around the office and tell everyone about how we understand LSP like a boss. And all is good… until we start trying to apply it to our work. If I can’t even change functionality on a simple setter without breaking the expectations on a parent class, what can I do with subtyping? Did Liskov just tell me to never touch subtyping again? The short answer: NO, SHE DIDN’T. When I first learned LSP, and from those I’ve talked with as well, I overlooked a very important but not appropriately stressed quality of the principle: our expectations. Our inclination is to want a logical catch-all, where we can easily apply this principle and wipe our hands, drop the mic and exit stage left. That’s not the case because in every different programming scenario, our expectations of the parent class or type will be different. We have to set reasonable expectations on the behaviors that we expect out of the parent, then make sure that those expectations are met by the child. Any expectations not explicitly expected of the parent aren’t expected of the child either, and don’t register as a violation of LSP that prevents implementation. You can see the flexibility mentioned in the Wikipedia article itself: A typical example that violates LSP is a Square class that derives from a Rectangle class, assuming getter and setter methods exist for both width and height. The Square class always assumes that the width is equal with the height. If a Square object is used in a context where a Rectangle is expected, unexpected behavior may occur because the dimensions of a Square cannot (or rather should not) be modified independently. This problem cannot be easily fixed: if we can modify the setter methods in the Square class so that they preserve the Square invariant (i.e., keep the dimensions equal), then these methods will weaken (violate) the postconditions for the Rectangle setters, which state that dimensions can be modified independently. Violations of LSP, like this one, may or may not be a problem in practice, depending on the postconditions or invariants that are actually expected by the code that uses classes violating LSP. Mutability is a key issue here. If Square and Rectangle had only getter methods (i.e., they were immutable objects), then no violation of LSP could occur. What this means is that the above situation with a rectangle and a square can be acceptable if we do not have the expectation for width to leave height unaffected, or vice-versa, in our application. Conclusion – the oft forgot third wheel Liskov Substitution Principle is meant to act as a guidance and warn us against unexpected behaviors. Objects can be stateful and as a result we can end up with unexpected situations if we don’t code carefully. Specifically when subclassing, make sure that the subclass meets the expectations held to its parent. Don’t let LSP think you cannot deviate from the behaviors of the parent, but understand that LSP is meant to highlight the importance of not only the parent and the child class, but also of the expectations WE set for the parent class and the necessity of meeting those expectations in order to help prevent sticky situations.   Code examples, in both VB and C# Technorati Tags: LSV,Liskov Substitution Principle,Uncle Bob,Robert Martin,Barbara Liskov,Liskov

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  • Advanced donut caching: using dynamically loaded controls

    - by DigiMortal
    Yesterday I solved one caching problem with local community portal. I enabled output cache on SharePoint Server 2007 to make site faster. Although caching works fine I needed to do some additional work because there are some controls that show different content to different users. In this example I will show you how to use “donut caching” with user controls – powerful way to drive some content around cache. About donut caching Donut caching means that although you are caching your content you have some holes in it so you can still affect the output that goes to user. By example you can cache front page on your site and still show welcome message that contains correct user name. To get better idea about donut caching I suggest you to read ScottGu posting Tip/Trick: Implement "Donut Caching" with the ASP.NET 2.0 Output Cache Substitution Feature. Basically donut caching uses ASP.NET substitution control. In output this control is replaced by string you return from static method bound to substitution control. Again, take a look at ScottGu blog posting I referred above. Problem If you look at Scott’s example it is pretty plain and easy by its output. All it does is it writes out current user name as string. Here are examples of my login area for anonymous and authenticated users:    It is clear that outputting mark-up for these views as string is pretty lame to implement in code at string level. Every little change in design will end up with new version of controls library because some parts of design “live” there. Solution: using user controls I worked out easy solution to my problem. I used cache substitution and user controls together. I have three user controls: LogInControl – this is the proxy control that checks which “real” control to load. AnonymousLogInControl – template and logic for anonymous users login area. AuthenticatedLogInControl – template and logic for authenticated users login area. This is the control we render for each user separately because it contains user name and user profile fill percent. Anonymous control is not very interesting because it is only about keeping mark-up in separate file. Interesting parts are LogInControl and AuthenticatedLogInControl. Creating proxy control The first thing was to create control that has substitution area where “real” control is loaded. This proxy control should also be available to decide which control to load. The definition of control is very primitive. <%@ Control EnableViewState="false" Inherits="MyPortal.Profiles.LogInControl" %> <asp:Substitution runat="server" MethodName="ShowLogInBox" /> But code is a little bit tricky. Based on current user instance we decide which login control to load. Then we create page instance and load our control through it. When control is loaded we will call DataBind() method. In this method we evaluate all fields in loaded control (it was best choice as Load and other events will not be fired). Take a look at the code. public static string ShowLogInBox(HttpContext context) {     var user = SPContext.Current.Web.CurrentUser;     string controlName;       if (user != null)         controlName = "AuthenticatedLogInControl.ascx";     else         controlName = "AnonymousLogInControl.ascx";       var path = "~/_controltemplates/" + controlName;     var output = new StringBuilder(10000);       using(var page = new Page())     using(var ctl = page.LoadControl(path))     using(var writer = new StringWriter(output))     using(var htmlWriter = new HtmlTextWriter(writer))     {         ctl.DataBind();         ctl.RenderControl(htmlWriter);     }     return output.ToString(); } When control is bound to data we ask to render it its contents to StringBuilder. Now we have the output of control as string and we can return it from our method. Of course, notice how correct I am with resources disposing. :) The method that returns contents for substitution control is static method that has no connection with control instance because hen page is read from cache there are no instances of controls available. Conclusion As you saw it was not very hard to use donut caching with user controls. Instead of writing mark-up of controls to static method that is bound to substitution control we can still use our user controls.

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  • WebForms vs MVC (again)

    There's a new video up on www.asp.net which aims to help developers pick between ASP.NET WebForms and ASP.NET MVC. The video boils down to 5 benefits per technology which Microsoft thinks you should consider. Let's go over the points, shall we? First, ASP.NET WebForms: 1 - Familiar control and event base programming model The claim here is that the ASP.NET model is comfortable for WinForm programmers (thankfully this unbiased analysis left out who it's more familiar for). This is largely...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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  • Is it okay to be generalist?

    - by Londoner
    I work at a ~50 employee company (UK), where all the technical people do a bit of everything. Specialising in anything for very long (6 months) is discouraged. For example, last week, I built a new Debian webserver, refactored some Perl, sat on a sales phone call, did a tape backup, reviewed code, built and deployed an RPM, gave opinions about x, y, z... With such a work scheme, I have gained a general knowledge how many things work, and pretty specific knowledge. I maybe program for 5 hours a week, despite officially being a developer. Does anyone else work like this, (or is this company unique)? Is it a problem to have skills developed in this way? (i.e. know a bit about everything in a certain domain, rather than know everything about say, one programming language?) Is it okay to be a generalist?

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  • StreamInsight/SSIS Integration White Paper

    - by Roman Schindlauer
    This has been tweeted all over the place, but we still want to give it proper attention here in our blog: SSIS (SQL Server Integration Service) is widely used by today’s customers to transform data from different sources and load into a SQL Server data warehouse or other targets. StreamInsight can process large amount of real-time as well as historical data, making it easy to do temporal and incremental processing.  We have put together a white paper to discuss how to bring StreamInsight and SSIS together and leverage both platforms to get crucial insights faster and easier. From the paper’s abstract: The purpose of this paper is to provide guidance for enriching data integration scenarios by integrating StreamInsight with SQL Server Integration Services. Specifically, we looked at the technical challenges and solutions for such integration, by using a case study based on a customer scenarios in the telecommunications sector. Please take a look at this paper and send us your feedback! Using SQL Server Integration Services and StreamInsight Together Regards, Ping Wang

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  • Game Engine which can provide 360 degree projection for PC

    - by Never Quit
    I'm searching Game engine which can provide 360 degree real-time projection. I've already achieved this by using VBS2 Game Engine. (Ref.: http://products.bisimulations.com/products/vbs2/vbs2-multi-channel). But I'm not satisfied with its graphics. So I'm looking for some other Game Engine which can do the same and provide me more better graphics and user experience. Like Frostbite2 or Unreal Engine 3. Like this image I want full 360 degree view. Is there any Game Engine which can provide 360 degree projection for PC? Thanks in advance...

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  • Python's Django or Delphi's IntraWeb?

    - by Azad Salahli
    Well, forgive me if it is an off-topic question. I have no knowledge about web programming, so I apologize in advance, if it is a stupid question. I will start to build a web based application. To be more specific, I will make a webpage which will have components like buttons, textboxes and etc. It will use a database to store information. My question is, which one is better to learn for that purpose? Python's Django or Delphi's IntraWeb? I know both Delphi and Python(although I know Delphi better).

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  • Professional WCF 4.0: Windows Communication Foundation with .NET 4.0

    - by cibrax
    The book in which I been working on since last year finally went to the light this week. It has been the result of hard work between me and three other Connected Systems MVP, my friend Fabio Cozzolino, Kurt Claeys and Johann Grabner. If you are interested in learning the new features in WCF 4.0, but also WCF in general and how to apply in real world scenarios, this book is for you. I dedicated three chapters of this book to one of my favorites topics, Security, from the basics to more complicated scenarios with Claim-Based security and Federated authentication using WCF services with Windows Identity Foundation. You can find more information about the book and the table of contents in the Wrox web site here.

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  • Best PHP-based web development 'stack' of 2011

    - by Jens Roland
    I have been building PHP-based web sites for many years, and lately it seems I'm discovering another interesting new tool or method once every few weeks. This begs the question - what is the current state of the art in PHP development stacks for the seasoned coder? I'm specifically interested in the following: High-performance web server Database MVC framework Build tool Revision control Continuous Integration Automated testing Non-persistent caching I'd like to optimize my stack for scalability and rapid development. I'm not looking for personal preference here, I'm looking for real, quantifiable reasons to pick this-over-that.

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  • How to hire a web-programmer : for non-programmer

    - by 0Complex
    I am a non-programmer that has used the services of : freelancer, odesk, etc I've tried asking for what i need but, I can't find anyone who can show me any type of example similar to what I request in the specs for the web-programming. They have front ends and back ends, but they don't fulfill true "live" website requirements. "live" as to be ready to support traffic, keys in hand, can be updated constantly by me, ... How do I figure how to evaluate a programmer ? How do I bid the appropriate price for the services ?

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  • GDC 2012: From Console to Chrome

    GDC 2012: From Console to Chrome (Pre-recorded GDC content) Cutting-edge HTML5 brings high performance console-style 3d games to the browser, but developing a modern HTML5 game engine can be a challenge. Adapting to HTML5 and Javascript can be bewildering to game programmers coming from C / C++. This talk is an overview of the tools, techniques, and topics you need to be familiar with to adapt to programming high performance 3D games for the web. Topics will include cutting edge HTML5 APIs, writing high performance Javascript, and profiling / debugging tools. Speaker: Lilli Thompson From: GoogleDevelopers Views: 3845 80 ratings Time: 01:02:14 More in Science & Technology

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  • Professional WCF 4.0: Windows Communication Foundation with .NET 4.0

    The book in which I been working on since last year finally went to the light this week. It has been the result of hard work between me and three other Connected Systems MVP, my friend Fabio Cozzolino, Kurt Claeys and Johann Grabner. If you are interested in learning the new features in WCF 4.0, but also WCF in general and how to apply in real world scenarios, this book is for you. I dedicated three chapters of this book to one of my favorites topics, Security, from the basics to more complicated...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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  • Loading dynamic content and rewrite URL on Hashchange event with Jquery Mobile

    - by user3611500
    I'm building a mobile version for my website using Jquery Mobile API. The framework provides automate AJAX navigation processing. But as far as i know it require "real" pages for loading purpose. What i want to do is override the automate navigation process of it and process the hashchange on my own. But i can't not rewrite the url using window.hashChange, which is running well on my non-mobile website version : $(function () { $(window).off().hashchange(function () { if (location.hash.length > 1) { PageSelect(); } }); $(window).hashchange(); }); I just only want to take advantage on jquery mobile interfaces, i don't want anything with its automate ajax navigation stuff ! I tried to disable it using ajaxEnabled() but got no luck.

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  • Are technical books easy to read on the Kindle (or other small screens) [closed]

    - by Peter Recore
    Possible Duplicate: eBook editions of programming books I am considering getting a kindle or other e reader. (Kindle is my top choice for the eink vs lcd factor) I have been able to try reading fiction on a Kindle, and it seemed pretty nice, even with the small screen. However, most books I buy are actually technical books, which tend to have figures, code samples, and other odd things. How well do the various ereaders handle books like this? In particular, does the kindle render code samples or figures in an easy to read way?

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