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• c# - what approach can I use to extend a group of classes that include implemented methods? (see des

  - by Greg

  Hi, I want to create an extendible package I am writing that has Topology, Node & Relationship classes. The idea is these base classes would have the various methods in them necessary to base graph traversal methods etc. I would then like to be able to reuse this by extending the package. For example the base requirements might see Relationship with a parentNode & childNode. Topology would have a List of Nodes and List of Relationships. Topology would have methods like FindChildren(int depth). Then the usage would be to extend these such that additional attributes for Node and Relationships could be added etc. QUESTION - What would be the best approach to package & expose the base level classes/methods? (it's kind of like a custom collection but with multiple facets). Would the following concepts come into play: Interfaces - would this be a good idea to have ITopology, INode etc, or is this not required as the user would extend these classes anyway? Abstract Classes - would the base classes be abstract classes Custom Generic Collection - would some approach using this concept assist (but how would this work if there are the 3 different classes) thanks

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• Search engine recommendation for 100 sites of about 4000 pages

  - by fwkb

  I am looking for a search engine that can regularly (daily-ish) scan about 100 pages for changes and index an associated site if changes since the last scan are found. It should be able to handle about 100 sites, each averaging 4000 pages of about 5k average size, each on a different server (but only the one centralized search engine). Each of these sites will have a search form that gets submitted to this search engine. The results that are returned must be specific to the site that submitted them. I create the templates for the external sites, so I can give the search form a hidden field that specifies which site the form is submitted from. What would you recommend I look into? I would love to use a Python-based system for this, if feasible. I am currently using something called iSearch2. It doesn't seem very stable at this scale, the description of the product states it is not really intended to do multiple sites, is in PHP (which is less comfortable to me than Python), and has a few other shortcomings for my specific situation.

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• How do I do distributed UML development (à la FOSS)?

  - by James A. Rosen

  I have a UML project (built in IBM's Rational System Architect/Modeler, so stored in their XML format) that has grown quite large. Additionally, it now contains several pieces that other groups would like to re-use. I come from a software development (especially FOSS) background, and am trying to understand how to use that as an analogy here. The problem I am grappling with is similar to the Fragile Base Class problem. Let me start with how it works in an object-oriented (say, Java or Ruby) FOSS ecosystem: Group 1 publishes some "core" package, say "net/smtp version 1.0" Group 2 includes Group 1's net/smtp 1.0 package in the vendor library of their software project At some point, Group 1 creates a new 2.0 branch of net/smtp that breaks backwards compatibility (say, it removes an old class or method, or moves a class from one package to another). They tell users of the 1.0 version that it will be deprecated in one year. Group 2, when they have the time, updates to net/smtp 2.0. When they drop in the new package, their compiler (or test suite, for Ruby) tells them about the incompatibility. They do have to make some manual changes, but all of the changes are in the code, in plain text, a medium with which they are quite familiar. Plus, they can often use their IDE's (or text editor's) "global-search-and-replace" function once they figure out what the fixes are. When we try to apply this model to UML in RSA, we run into some problems. RSA supports some fairly powerful refactorings, but they seem to only work if you have write access to all of the pieces. If I rename a class in one package, RSA can rename the references, but only at the same time. It's very difficult to look at the underlying source (the XML) and figure out what's broken. To fix such a problem in the RSA editor itself means tons of clicking on things -- there is no good equivalent of "global-search-and-replace," at least not after an incomplete refactor. They real sticking point seems to be that RSA assumes that you want to do all your editing using their GUI, but that makes certain operations prohibitively difficult. Does anyone have examples of open-source UML projects that have overcome this problem? What strategies do they use for communicating changes?

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• Is this BlockingQueue susceptible to deadlock?

  - by unforgiven3

  I've been using this code as a queue that blocks on Dequeue() until an element is enqueued. I've used this code for a few years now in several projects, all with no issues... until now. I'm seeing a deadlock in some code I'm writing now, and in investigating the problem, my 'eye of suspicion' has settled on this BlockingQueue<T>. I can't prove it, so I figured I'd ask some people smarter than me to review it for potential issues. Can you guys see anything that might cause a deadlock in this code? public class BlockingQueue<T> { private readonly Queue<T> _queue; private readonly ManualResetEvent _event; /// <summary> /// Constructor /// </summary> public BlockingQueue() { _queue = new Queue<T>(); _event = new ManualResetEvent(false); } /// <summary> /// Read-only property to get the size of the queue /// </summary> public int Size { get { int count; lock (_queue) { count = _queue.Count; } return count; } } /// <summary> /// Enqueues element on the queue /// </summary> /// <param name="element">Element to enqueue</param> public void Enqueue(T element) { lock (_queue) { _queue.Enqueue(element); _event.Set(); } } /// <summary> /// Dequeues an element from the queue /// </summary> /// <returns>Dequeued element</returns> public T Dequeue() { T element; while (true) { if (Size == 0) { _event.Reset(); _event.WaitOne(); } lock (_queue) { if (_queue.Count == 0) continue; element = _queue.Dequeue(); break; } } return element; } /// <summary> /// Clears the queue /// </summary> public void Clear() { lock (_queue) { _queue.Clear(); } } }

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• div content margin pushing container

  - by jef2904

  Hi, Im running into an issue that's really baffleing me. I have a container that I want to apply a background to an postion it in the top right of the browser screen. The div inside has a top margin of 4em and this is pushing the container div here is the CSS #container { background: transparent url("../images/house-bg.png") top right no-repeat scroll; } #wrapper { background: #FFF; width: 960px; height: 600px; margin: 4em auto 0; border: 10px solid #C3CF21; -moz-border-radius: 20px; -webkit-border-radius: 20px; border-radius: 20px; -moz-box-shadow: 0 0 25px #444; -webkit-box-shadow: 0 0 25px #444; box-shadow: 0 0 25px #444; } and heres the HTML <div id="container"> <div id="wrapper"> <div id="header"> </div> <div id="main"> </div> </div> <div id="footer"> &copy; Copyright <?php echo date("Y");?> Company, Inc. </div> </div> I want the margin of the wrapper to be inside the container div instead of outside. I've tried multiple display properties and position properties to no avail. The only thing that fixes it is inserting an "&nbsp;" before the start of the #wrapper but theres got to be a CSS fix to this. Thanks in Advanced, Jorge

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• Working with friends. Poor career choice?

  - by a_person

  Hi all, Hope you can help me solve somewhat of a moral dilemma. Some time ago, after just a few years of living in U.S. and having to take any job I could get my hands on a friend of mine submitted recommended me for an open position at the company that he was working for. I could have not been happier. I do not have a degree of any sort, however, by being passionate about CS and with constant drive for self education I've became a somewhat of a strong generalist. Every place I worked for recognized me for that quality and used me on various projects where set of technology in hand had no overlap with set of knowledge of the team members. Rapidly I've advanced to Sr. Programmer position and the trend of me following a friend from one place to another have started and continued on for a few years. My friend's goal always been to become an IT Director, mine is to become the best programmer I can be. To my knowledge I've accommodated his goals as much as I could by taking a back seat, and letting him take the lead. Fast forward to today. He's a manager, and I am on his team. I am unhappy and I in considerable amount of suffering. I am not being utilized to my potential, it's almost exact opposite, I am being micromanaged to an unhealthy extent, my decisions, and suggestions are constantly met with negative connotation. Last week I had to hear about how my friend is a better programmer than I am. My ego was ecstatic about this one /s. In addition to that working in the field of BI have exhausted itself for most parts. The only pleasure of my work is being derived from making everything as dynamic and parameter driven as possible. This is the only area where a friend of mine does not feel competent enough to actually micromanage. Because of my situation I feel a fair amount of guilt and ever growing resentment. I need your advice, maybe you've dealt with this expression of ego before, needs of self vs the needs of your friend. Is working with a friend a poor choice? Thank you for reading in.

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• Trying to make a plugin system in C++/Qt

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• Is memory allocation in linux non-blocking?

  - by Mark

  I am curious to know if the allocating memory using a default new operator is a non-blocking operation. e.g. struct Node { int a,b; }; ... Node foo = new Node(); If multiple threads tried to create a new Node and if one of them was suspended by the OS in the middle of allocation, would it block other threads from making progress? The reason why I ask is because I had a concurrent data structure that created new nodes. I then modified the algorithm to recycle the nodes. The throughput performance of the two algorithms was virtually identical on a 24 core machine. However, I then created an interference program that ran on all the system cores in order to create as much OS pre-emption as possible. The throughput performance of the algorithm that created new nodes decreased by a factor of 5 relative the the algorithm that recycled nodes. I'm curious to know why this would occur. Thanks. *Edit : pointing me to the code for the c++ memory allocator for linux would be helpful as well. I tried looking before posting this question, but had trouble finding it.

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• ZeroMQ REQ/REP on ipc:// and concurrency

  - by Metiu

  I implemented a JSON-RPC server using a REQ/REP 0MQ ipc:// socket and I'm experiencing strange behavior which I suspect is due to the fact that the ipc:// underlying unix socket is not a real socket, but rather a single pipe. From the documentation, one has to enforce strict zmq_send()/zmq_recv() alternation, otherwise the out-of-order zmq_send() will return an error. However, I expected the enforcement to be per-client, not per-socket. Of course with a Unix socket there is just one pipeline from multiple clients to the server, so the server won't know who it is talking with. Two clients could zmq_send() simultaneously and the server would see this as an alternation violation. The sequence could be: ClientA: zmq_send() ClientB: zmq_send() : will it block until the other send/receive completes? will it return -1? (I suspect it will with ipc:// due to inherent low-level problems, but with TCP it could distinguish the two clients) ClientA: zmq_recv() ClientB: zmq_recv() so what about tcp:// sockets? Will it work concurrently? Should I use some other locking mechanism to work around this?

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• How to properly implement the Strategy pattern in a web MVC framework?

  - by jboxer

  In my Django app, I have a model (lets call it Foo) with a field called "type". I'd like to use Foo.type to indicate what type the specific instance of Foo is (possible choices are "Number", "Date", "Single Line of Text", "Multiple Lines of Text", and a few others). There are two things I'd like the "type" field to end up affecting; the way a value is converted from its normal type to text (for example, in "Date", it may be str(the_date.isoformat())), and the way a value is converted from text to the specified type (in "Date", it may be datetime.date.fromtimestamp(the_text)). To me, this seems like the Strategy pattern (I may be completely wrong, and feel free to correct me if I am). My question is, what's the proper way to code this in a web MVC framework? In a client-side app, I'd create a Type class with abstract methods "serialize()" and "unserialize()", override those methods in subclasses of Type (such as NumberType and DateType), and dynamically set the "type" field of a newly-instantiated Foo to the appropriate Type subclass at runtime. In a web framework, it's not quite as straightforward for me. Right now, the way that makes the most sense is to define Foo.type as a Small Integer field and define a limited set of choices (0 = "Number", 1 = "Date", 2 = "Single Line of Text", etc.) in the code. Then, when a Foo object is instantiated, use a Factory method to look at the value of the instance's "type" field and plug in the correct Type subclass (as described in the paragraph above). Foo would also have serialize() and unserialize() methods, which would delegate directly to the plugged-in Type subclass. How does this design sound? I've never run into this issue before, so I'd really like to know if other people have, and how they've solved it.

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• Programming an IPTV application- Client/Server

  - by Sumit Ghosh

  I am part of a team which has been given a task to deploy an IPTV solution for a company. The system has been architect-ed like this. There is Video capture card , which receives satellite signals from a satellite receiver. This video capture card is part of a windows 7 machine. The signals need to be trans coded here and passed to a streaming server which will be received by end users. The end users will be desktop users having a C#.NET application installed to view the channels. I am confused at the choice of server software as I have multiple choices - Windows Media Server, VideoLan (VLC project), or Flash Media Server, it also supports MPEG-2 HD. My main aim to be able to stream MPEG-2 channels with HD quality and encrypt the channels at the server end so that the streams can be protected. I know reversing is possible but it wont be easy as for every naive user with wireshark snooping my streams. If any of you here has ever done such an implementation please do suggest me the best technologies I should go for. Iam open to C#,C++ and other similar languages. Any help shall be deeply appreciated. edit: End Users shall be part of Internet and not necessarily a lan, reason for this question is internet doesn't support multicast like Lan, so I need some suggestions.

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• Positioning decorated series of div tags on screen using offset, DOM JQUERY RELATED

  - by Calibre2010

  Hi, I am using JQuery to position a series of div tags which basically use a class inside of the tag which decorates the divs as bars. So the div is a green box based on its css specifications to the glass. I have a list of STARTING postions, a list of left coordiantes- for the starting points I wish to position my DIV say 556, 560, 600 these automatically are generated as left positions in a list I have a list of ENDING postions, a list of left coordiantes- for the ending points I wish to position my DIV say 570, 590, 610 these automatically are generated as left positions in a list now for each start and end position, the bar(green box) i want to be drawn with its appropriate width as follows. so say f is the offset or position of the start and ff the offset or position of the end : Below draws the green box based on only one start and end position LEFT. if (f.left != 0) { $("#test").html($("<div>d</div>")).css({ position: 'absolute', left: (f.left) + "px", top: (f.top + 35) + "px", width: (ff.left - f.left) + 25 + "px" }).addClass("option1"); } I am looking to loop through the list of positons in the list and draw multiple green boxs based on the positions on the screen. The above code draws just one green box from the last offset position.

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• Sharing same vector control between different places

  - by Alexander K

  Hi everyone, I'm trying to implement the following: I have an Items Manager, that has an Item class inside. Item class can store two possible visual representations of it - BitmapImage(bitmap) and UserControl(vector). Then later, in the game, I need to share the same image or vector control between all possible places it takes place. For example, consider 10 trees on the map, and all point to the same vector control. Or in some cases this can be bitmap image source. So, the problem is that BitmapImage source can be easily shared in the application by multiple UIElements. However, when I try to share vector control, it fails, and says Child Element is already a Child element of another control. I want to know how to organize this in the best way. For example replace UserControl with other type of control, or storage, however I need to be sure it supports Storyboard animations inside. The code looks like this: if (bi.item.BitmapSource != null) { Image previewImage = new Image(); previewImage.Source = bi.item.BitmapSource; itemPane.ItemPreviewCanvas.Children.Add(previewImage); } else if (bi.item.VectorSource != null) { UserControl previewControl = bi.item.VectorSource; itemPane.ItemPreviewCanvas.Children.Add(previewControl); } Thanks in advance

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• Where do objects merge/join data in a 3-tier model?

  - by BerggreenDK

  Its probarbly a simple 3-tier problem. I just want to make sure we use the best practice for this and I am not that familiary with the structures yet. We have the 3 tiers: GUI: ASP.NET for Presentation-layer (first platform) BAL: Business-layer will be handling the logic on a webserver in C#, so we both can use it for webforms/MVC + webservices DAL: LINQ to SQL in the Data-layer, returning BusinessObjects not LINQ. DB: The SQL will be Microsoft SQL-server/Express (havent decided yet). Lets think of setup where we have a database of [Persons]. They can all have multiple [Address]es and we have a complete list of all [PostalCode] and corresponding citynames etc. The deal is that we have joined a lot of details from other tables. {Relations}/[tables] [Person]:1 --- N:{PersonAddress}:M --- 1:[Address] [Address]:N --- 1:[PostalCode] Now we want to build the DAL for Person. How should the PersonBO look and when does the joins occure? Is it a business-layer problem to fetch all citynames and possible addressses pr. Person? or should the DAL complete all this before returning the PersonBO to the BAL ? Class PersonBO { public int ID {get;set;} public string Name {get;set;} public List<AddressBO> {get;set;} // Question #1 } // Q1: do we retrieve the objects before returning the PersonBO and should it be an Array instead? or is this totally wrong for n-tier/3-tier?? Class AddressBO { public int ID {get;set;} public string StreetName {get;set;} public int PostalCode {get;set;} // Question #2 } // Q2: do we make the lookup or just leave the PostalCode for later lookup? Can anyone explain in what order to pull which objects? Constructive criticism is very welcome. :o)

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• SSRS code variable resetting on new page

  - by edmicman

  In SSRS 2008 I am trying to maintain a SUM of SUMs on a group using custom Code. The reason is that I have a table of data, grouped and returning SUMs of the data. I have a filter on the group to remove lines where group sums are zero. Everything works except I'm running into problems with the group totals - it should be summing the visible group totals but is instead summing the entire dataset. There's tons of articles about how to work around this, usually using custom code. I've made custom functions and variables to maintain a counter: Public Dim GroupMedTotal as Integer Public Dim GrandMedTotal as Integer Public Function CalcMedTotal(ThisValue as Integer) as Integer GroupMedTotal = GroupMedTotal + ThisValue GrandMedTotal = GrandMedTotal + ThisValue Return ThisValue End Function Public Function ReturnMedSubtotal() as Integer Dim ThisValue as Integer = GroupMedTotal GroupMedTotal = 0 Return ThisValue End Function Basically CalcMedTotal is fed a SUM of a group, and maintains a running total of that sum. Then in the group total line I output ReturnMedSubtotal which is supposed to give me the accumulated total and reset it for the next group. This actually works great, EXCEPT - it is resetting the GroupMedTotal value on each page break. I don't have page breaks explicitly set, it's just the natural break in the SSRS viewer. And if I export the results to Excel everything works and looks correctly. If I output Code.GroupMedTotal on each group row, I see it count correctly, and then if a group spans multiple pages on the next page GroupMedTotal is reset and begins counting from zero again. Any help in what's going on or how to work around this? Thanks!

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• SQLBrowser will not start

  - by Oliver

  SQL Server 2005 x64 on Windows Server 2003 x64, with multiple instances (default + 2 named). Engineers moved server to a different domain. Since then, cannot get SQLBrowser to start. Still able to query the default instance, and can access named instances by port (TCP:hostname,port#). When on server, can use SSMS to connect to the instances, all is well from that perspective. No errors in the SQL Server logs. As SQLBrowser is starting, an entry in EventViewer.Application says that one of the named instances has an invalid configuration, but I haven't been able to figure out what is invalid. Startup continues, and next message says "The SQLBrowser service was unable to establish SQL instance and connectivity discovery." Next, it enables instance and connectivity discovery support; next, another message about that same named instance having an invalid configuration; then an event says that SQLBrowser has started; last, an event shows the SQLBrowser service has shutdown. I got SQLBrowser to get past the issue with the first named instance by temporarily renaming a registry entry, and now the second named instance can be accessed by name rather than port. Still, cannot access the first named instance by name. Advice?

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• Better way to implement custom views in a listview with simpleadapter?

  - by jonaz

  I have a value called tags which is a comma separated list of words. I want to put this into nicely designed "tag-buttons". The below works. However the line ((LinearLayout) view).removeAllViews(); seems like an ugly fix for not adding the tags multiple times every time adapter.notifyDataSetChanged(); is called after i load more rows with a setOnScrollListener() Any suggestion to "best practice" here, or at least a more good looking solution? adapter = new SimpleAdapter(activity,data, R.layout.list_transactions, new String[] {"comment", "amount","date","tags","category"}, new int[] { R.id.comment, R.id.amount,R.id.date,R.id.tags_container,R.id.category } ); SimpleAdapter.ViewBinder binder = new SimpleAdapter.ViewBinder() { @Override public boolean setViewValue(View view, Object object, String value) { //Log.d(TAG,"view.toString()= "+ view.toString()); if (view.getId() == R.id.tags_container) { String[] tags = value.split(","); ((LinearLayout) view).removeAllViews(); for (String tag : tags) { View v = createTagView(activity.getLayoutInflater(),tag); ((LinearLayout) view).addView(v); } return true; } return false; } };

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• How to Treat Race Condition of Session in Web Application?

  - by Morgan Cheng

  I was in a ASP.NET application has heavy traffic of AJAX requests. Once a user login our web application, a session is created to store information of this user's state. Currently, our solution to keep session data consistent is quite simple and brutal: each request needs to acquire a exclusive lock before being processed. This works fine for tradition web application. But, when the web application turns to support AJAX, it turns to not efficient. It is quite possible that multiple AJAX requests are sent to server at the same time without reloading the web page. If all AJAX requests are serialized by the exclusive lock, the response is not so quick. Anyway, many AJAX requests that doesn't access same session variables are blocked as well. If we don't have a exclusive lock for each requests, then we need to treat all race condition carefully to avoid dead lock. I'm afraid that would make the code complex and buggy. So, is there any best practice to keep session data consistent and keep code simple and clean?

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• Database structure for ecommerce site

  - by imanc

  Hey Guys, I have been tasked with designing an ecommerce solution. The aspect that is causing me the most problems is the database. Currently the site consists of 10+ country based shops each with their own database (all residing on the same mysql instance). For the new site I'd rather all these shop databases be merged into one database so that all tables (products, orders, customers etc.) have a shop_id field. From a programming perspective this seems to make the most sense as we won't have to manage data across multiple databases. Currently the entire site generates about 120k orders a year, but is experiencing fairly heavy growth and we need to design a solution that will scale. In 5 years there may be more than a million orders per year and a database that contains 5 years order history (archiving maybe a solution here). The question is - do we use a single database, or do we keep the database-per-shop structure? I am currently trying to find supporting evidence for either avenue. The company I am designing the solution for prefer the per-shop database structure because they believe it will allow the sites to scale. But my argument is that the shop's database probably won't get that busy over the next few years that they exceed the capacity of a mysql database and a "no expenses spared" hardware set-up. I am wondering if anyone has any advice either way? Does anyone have experience with websites / ecommerce sites that have tables containing millions of records? I know there is probably not a clear answer here, but at what stage do we have too many records or too large table files to have a fast loading site? Also, if anyone has any advice on sources of information - books, websites, etc. where I can do further research, it would be highly appreciated! Cheers, imanc

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• Is a Multi-DAL Approach the way to go here?

  - by Krisc

  Working on the data access / model layer in this little MVC2 project and trying to think things out to future projects. I have a database with some basic tables and I have classes in the model layer that represent them. I obviously need something to connect the two. The easiest is to provide some sort of 'provider' that can run operations on the database and return objects. But this is for a website that would potentially be used "a lot" (I know, very general) so I want to cache results from the data layer and keep the cache updated as new data is generated. This question deals with how best to approach this problem of dual DALS. One that returns cached data when possible and goes to the data layer when there is a cache miss. But more importantly, how to integrate the core provider (thing that goes into database) with the caching layer so that it too can rely on cached objects rather than creating new ones. Right now I have the following interfaces: IDataProvider is used to reach the database. It doesn't concern itself with the meaning of the objects it produces, but simply the way to produce them. interface IDataProvider{ // Select, Update, Create, et cetera access IEnumerable<Entry> GetEntries(); Entry GetEntryById(int id); } IDataManager is a layer that sits on top of the IDataProvider layer and manages the cache interface IDataManager : IDataProvider{ void ClearCache(); } Note that in practice the IDataManager implementation will have useful helper functions to add objects to their related cache stores. (In the future I may define other functions on the interface) I guess what I am looking for is the best way to approach a loop back from the IDataProvider implementations so that they can access the cache. Or a different approach entirely may be in order? I am not very interested in 3rd party products at the moment as I am interested in the design of these things much more than this specific implementation. Edit: I realize the title may be a bit misleading. I apologize for that... not sure what to call this question.

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• ADO Exception in HQL query

  - by Yoav

  I have 2 classes: Project and DataStructure. Class Project contains member List<DataStructure. My goal is to load a Project and all its DataStructures in one call. public class Project { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual ISet<DataStructure> DataStructures { get { } set { } } } public class DataStructure { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual string Description { get { } set { } } public virtual Project Project { get { } set { } } public virtual IList<DataField> Fields { get { } set { } } } Note that DataStructure also contains a list of class DataField but I don’t want to load these right now. Mapping in Fluent NHibernate: public class ProjectMap : ClassMap<Project> { public ProjectMap() { Table("PROJECTS"); Id(x => x.Pk, "PK"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); HasMany<DataStructure>(x => x.DataStructures).KeyColumn("FK_PROJECT"); } } public class DataStructureMap : ClassMap<DataStructure> { public DataStructureMap() { Table("DATA_STRUCTURES"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); Map(x => x.Description, "DESCRIPTION"); References<Project>(x => x.Project, "FK_PROJECT"); HasMany<DataField>(x => x.Fields).KeyColumn("FK_DATA_STRUCTURE"); } } This is my query: using (ISession session = SessionFactory.OpenSession()) { IQuery query = session.CreateQuery("from Project pr left join pr.DataStructure"); project = query.List<Project>(); } query.List() returns this exception: NHibernate.Exceptions.GenericADOException: Could not execute query[SQL: SQL not available] ---> System.ArgumentException: The value "System.Object[]" is not of type "Project" and cannot be used in this generic collection.

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• Going "behind Hibernate's back" to update foreign key values without an associated entity

  - by Alex Cruise

  Updated: I wound up "solving" the problem by doing the opposite! I now have the entity reference field set as read-only (insertable=false updatable=false), and the foreign key field read-write. This means I need to take special care when saving new entities, but on querying, the entity properties get resolved for me. I have a bidirectional one-to-many association in my domain model, where I'm using JPA annotations and Hibernate as the persistence provider. It's pretty much your bog-standard parent/child configuration, with one difference being that I want to expose the parent's foreign key as a separate property of the child alongside the reference to a parent instance, like so: @Entity public class Child { @Id @GeneratedValue Long id; @Column(name="parent_id", insertable=false, updatable=false) private Long parentId; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name="parent_id") private Parent parent; private long timestamp; } @Entity public class Parent { @Id @GeneratedValue Long id; @OrderBy("timestamp") @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY) private List<Child> children; } This works just fine most of the time, but there are many (legacy) cases when I'd like to put an invalid value in the parent_id column without having to create a bogus Parent first. Unfortunately, Hibernate won't save values assigned to the parentId field due to insertable=false, updatable=false, which it requires when the same column is mapped to multiple properties. Is there any nice way to "go behind Hibernate's back" and sneak values into that field without having to drop down to JDBC or implement an interceptor? Thanks!

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• Dependent Dropdowns with single class element

  - by AJ

  I am trying to create multiple dependent dropdowns (selects) with a unique way. I want to restrict the use of selectors and want to achieve this by using a single class selectors on all SELECTs; by figuring out the SELECT that was changed by its index. Hence, the SELECT[i] that changed will change the SELECT[i+1] only (and not the previous ones like SELECT[i-1]). For html like this: <select class="someclass"> <option value="volvo">Volvo</option> <option value="saab">Saab</option> <option value="mercedes">Mercedes</option> <option value="audi">Audi</option> </select> <select class="someclass"> </select> <select class="someclass"> </select> where the SELECTs other than the first one will get something via AJAX. I see that the following Javascript gives me correct value of the correct SELECT and the value of i also corresponds to the correct SELECT. $(function() { $(".someclass").each(function(i) { $(this).change(function(x) { alert($(this).val() + i); }); }); }); Please note that I really want the minimum selector approach. I just cannot wrap my head around on how to approach this. Should I use Arrays? Like store all the SELECTS in an Array first and then select those? I believe that since the above code already passes the index i, there should be a way without Arrays also. Thanks a bunch. AJ

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• Enum exeeding the 65535 bytes limit of static initializer... what's best to do?

  - by Daniel Bleisteiner

  I've started a rather large Enum of so called Descriptors that I've wanted to use as a reference list in my model. But now I've come across a compiler/VM limit the first time and so I'm looking for the best solution to handle this. Here is my error : The code for the static initializer is exceeding the 65535 bytes limit It is clear where this comes from - my Enum simply has far to much elements. But I need those elements - there is no way to reduce that set. Initialy I've planed to use a single Enum because I want to make sure that all elements within the Enum are unique. It is used in a Hibernate persistence context where the reference to the Enum is stored as String value in the database. So this must be unique! The content of my Enum can be devided into several groups of elements belonging together. But splitting the Enum would remove the unique safety I get during compile time. Or can this be achieved with multiple Enums in some way? My only current idea is to define some Interface called Descriptor and code several Enums implementing it. This way I hope to be able to use the Hibernate Enum mapping as if it were a single Enum. But I'm not even sure if this will work. And I loose unique safety. Any ideas how to handle that case?

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• Using shared_ptr to implement RCU (read-copy-update)?

  - by yongsun

  I'm very interested in the user-space RCU (read-copy-update), and trying to simulate one via tr1::shared_ptr, here is the code, while I'm really a newbie in concurrent programming, would some experts help me to review? The basic idea is, reader calls get_reading_copy() to gain the pointer of current protected data (let's say it's generation one, or G1). writer calls get_updating_copy() to gain a copy of the G1 (let's say it's G2), and only one writer is allowed to enter the critical section. After the updating is done, writer calls update() to do a swap, and make the m_data_ptr pointing to data G2. The ongoing readers and the writer now hold the shared_ptr of G1, and either a reader or a writer will eventually deallocate the G1 data. Any new readers would get the pointer to G2, and a new writer would get the copy of G2 (let's say G3). It's possible the G1 is not released yet, so multiple generations of data my co-exists. template <typename T> class rcu_protected { public: typedef T type; typedef std::tr1::shared_ptr<type> rcu_pointer; rcu_protected() : m_data_ptr (new type()) {} rcu_pointer get_reading_copy () { spin_until_eq (m_is_swapping, 0); return m_data_ptr; } rcu_pointer get_updating_copy () { spin_until_eq (m_is_swapping, 0); while (!CAS (m_is_writing, 0, 1)) {/* do sleep for back-off when exceeding maximum retry times */} rcu_pointer new_data_ptr(new type(*m_data_ptr)); // as spin_until_eq does not have memory barrier protection, // we need to place a read barrier to protect the loading of // new_data_ptr not to be re-ordered before its construction _ReadBarrier(); return new_data_ptr; } void update (rcu_pointer new_data_ptr) { while (!CAS (m_is_swapping, 0, 1)) {} m_data_ptr.swap (new_data_ptr); // as spin_until_eq does not have memory barrier protection, // we need to place a write barrier to protect the assignments of // m_is_writing/m_is_swapping be re-ordered bofore the swapping _WriteBarrier(); m_is_writing = 0; m_is_swapping = 0; } private: volatile long m_is_writing; volatile long m_is_swapping; rcu_pointer m_data_ptr; };

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