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• How do I obtain a new stateful session bean in a servlet thread?

  - by FarmBoy

  I'm experimenting with EJB3 I would like to inject a stateful session bean into a servlet, so that each user that hits the servlet would obtain a new bean. Obviously, I can't let the bean be an instance variable for the servlet, as that will be shared. And apparantly injecting local variables isn't allowed. I can use the new operator to create a bean, but that doesn't seem the right approach. Is there a right way to do this? It seems like what I'm trying to do is fairly straightforward, after all, we would want each new customer to find an empty shopping cart.

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• Jinja2 returns "None" string for Google App Engine models

  - by Brian M. Hunt

  Google App Engine models, likeso: from google.appengine.ext.db import Model class M(): name = db.StringProperty() Then in a Jinja2 template called from a Django view with an in instance of M passed in as m: The name of this M is {{ m.name }}. When m is initialized without name being set, the following is printed: The name of this M is None. The preferable and expected output (and the output when using Django templates) would be/is: The name of this M is . Do you know why this is happening, and how to get the preferred & expected output?

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• PBKDF2-HMAC-SHA1

  - by Jason

  To generate a valid pairwise master key for a WPA2 network a router uses the PBKDF2-HMAC-SHA1 algorithm. I understand that the sha1 function is performed 4096 times to derive the PMK, however I have two questions about the process. Excuse the pseudo code. 1) How is the input to the first instance of the SHA1 function formatted? SHA1("network_name"+"network_name_length"+"network_password") Is it formatted in that order, is it the hex value of the network name, length and password or straight ASCII? Then from what I gather the 160 bit digest received is fed straight into another round of hashing without any additional salting. Like this: SHA1("160bit digest from last round of hashing") Rise and repeat. 2) Once this occurs 4096 times 256 bits of the output is used as the pairwise master key. What I don't understand is that if SHA1 produces 160bit output, how does the algorithm arrive at the 256bits required for a key? Thanks for the help.

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• Languages and development methodologies

  - by Carlos

  Having never worked with Ruby on Rails, I looked it up on Wikipedia. It says It is intended to be used with an Agile development methodology that is used by web developers for rapid development. This got me asking how a given language/framework can be more appropriate for given development methodologies. Are there certain languages that are more friendly for pair programming, for instance? Are there language features that make certain methodologies are more appropriate? Are there features that make certain methodologies impossible? My initial reaction is to dismiss the connection (the design process is a business process, which is more dependent on business needs that language features). But I'm an only programmer within the firm, and I'm a partner, so I get to decide the business needs. What do you think? Also, if the SO community finds that certain languages point towards certain methodologies, what methodology is most common for c#, which is what I use most of the time?

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• Where to delete model image?

  - by WesDec

  I have a Model with an image field and I want to be able to change the image using a ModelForm. When changing the image, the old image should be deleted and replaced by the new image. I have tried to do this in the clean method of the ModelForm like this: def clean(self): cleaned_data = super(ModelForm, self).clean() old_profile_image = self.instance.image if old_profile_image: old_profile_image.delete(save=False) return cleaned_data This works fine unless the file indicated by the user is not correct (for example if its not an image), which result in the image being deleted without any new images being saved. I would like to know where is the best place to delete the old image? By this I mean where can I be sure that the new image is correct before deleting the old one?

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• Null Reference Exception on MVVM pattern

  - by Mohit Deshpande

  System.NullReferenceException Object reference not set to an instance of an object. at Microsoft.Windows.Design.DocumentModel.Trees.MarkupDocumentTreeManager.<FindMarkupNodePath>d__0.MoveNext() at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source) at MS.Internal.Services.DocumentInformationServiceImpl.get_Root() at MS.Internal.Designer.VSDesigner.Load() at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedView.Load() at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedDesignerFactory.Load(IsolatedView view) at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view) at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view) at MS.Internal.Host.Isolation.IsolatedDesigner.Load() at MS.Internal.Designer.DesignerPane.LoadDesignerView() I keep getting this exception and then intellisense stops working in a XAML text editor. Any ideas why?

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• Should Java IOException have been an unchecked RuntimeException?

  - by Derek Mahar

  Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling this exception to a separate system error handler.

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• Loop through all subclasses in an Android view?

  - by Slapout

  I’m working on a game for Android. To help implement it, my idea is to create a subclass of a view. I would then insert several instances of this class as children of the main view. Each instance would handle detecting when it was pressed (via OnTouchListener). The problem I’m having now is how do I loop through all these sub-views so I can read their statuses and process them? (I.e. when they all reach a certain state something should happen). Or is there a better way to have several objects on the screen that respond to touch and whose status I can check?

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• Cannot Debug Visual Basic 6 ActiveX Component On 64-bit OS

  - by Humanier

  Hi, The situation might sound a bit weird but I have to play with what I have. There's a Win2003 64-bit server OS and a legacy application written using Visual Studio 6. The app consists of two parts: ActiveX components written in VB6 and C++ code which uses them. I need to debug the components' code. I installed Visual Studio 6 on the server and I'm able to step into the component's code. Then I got following situation: 1) C++ code works until it needs to instantiate component A. 2) At this step we switch to VB6 and start debugging Component's A. 3) In the very beginning component A creates an instance of a class C exposed by component B. At this step VB6 debugger shows error message with title "OLEDB32.DLL" and following text: "Failed to load resource DLL C:\Program Files (x86)\Common Files\System\Ole DB\OLEDB32R.DLL" Additional information: The last step in initialization of the class C is opening an ADO connection to SQL server using OLEDB provider. I'd appreciate any ideas on how resolve this problem. Thanks in advance.

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• Multiple MCs, Single Listener, AsBroadcaster

  - by Brett

  I'm currently working trying to have multiple MCs inside a container MC which when they mini MCs are clicked will broadcast a message so that I can act upon them. This would be simple in AS 3 as it would be mc.addEventListener(MouseEvent.CLICK, obj); however, this is AS 2 and so I am semi-forced to use the broadcastMessage('myMessage'); and mc.addListener(obj); event handler. The main problem is that the broadcaster isn't broadcasting any messages. The second problem is that there are 5 MCs and when I click one of them, I get 5 trace messages about the click. I can't seem to keep the MC clicks unique even though they are all given separate instance names vie the properties panel. Any help would be appreciated. A link to my code is here (pastie.org #481511). Can you see anything wrong?

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• LINQ query checks for null

  - by user300992

  I have a userList, some users don't have a name (null). If I run the first LINQ query, I got an error saying "object reference not set to an instance of an object" error. var temp = (from a in userList where ((a.name == "john") && (a.name != null)) select a).ToList(); However, if I switch the order by putting the checking for null in front, then it works without throwing any error: var temp = (from a in userList where ((a.name != null) && (a.name == "john")) select a).ToList(); Why is that? If that's pure C# code (not LINQ), I think both would be the same. I don't have SQL profiler, I am just curious what will be the difference when they are being translated on SQL level.

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• A quick design question about C++ container classes in shared memory

  - by recipriversexclusion

  I am writing a simple wrapper around boost::interprocess's vector container to implement a ring buffer in shared memory (shm) for IPC. Assume that buf is an instance of RingBuffer created in shm. Now, in its ctor, buf itself allocates a private boost::interprocess::vector data member to store values, e.g. m_data. My question is: I think m_data should also be created in shared memory. But it this a necessity? What happens if buf that was created in shm itself, allocates standard memory, i.e. using new. Does this get allocated on the calling process's heap? I don't think buf is allocated there so how come a data member that is private to an object not on a process's heap gets allocated there. I'm confused.

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• Objective-C: How to create a method that will return a UInt8 array from an int

  - by Adam

  I need to create an Objective-C method that converts an int into a byte array. In this instance, I can't use NSArray as a return type, it must be an UInt8 array. I've written a simple method to do this, but it has errors during compile and tells me that I have incompatible return types. Here is the code snippet. Any ideas? - (UInt8[])ConvertToBytes:(int) i { UInt8 *retVal[4]; retVal[0] = i >> 24; retVal[1] = i >> 16; retVal[2] = i >> 8; retVal[3] = i >> 0; return retVal; }

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• xml intellisense with Eclipse Europa?

  - by Maddy.Shik

  Please suggest some free tools or some in build feature in Eclipse for intellisense of xml. I am using Eclipse Europa which is for EE java developers. <?xml version ="1.0" encoding = "UTF-8"?> <tests xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://jtestcase.sourceforge.net/dtd/jtestcase2.xsd"> </tests> Xml code above is part of xml file i am working upon. I am expecting eclipse to suggest me tags based upon xsd specified above. I am using ctrl+space for suggestion of new tag. Please suggest if i am using wrong key for intellisense or am i missing some tool or plugin. Thanks

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• How to change line thickness in iText?

  - by drasto

  I'm drawing images to pdf using Java framework iText. I need to draw lines of specified width. There is a method setLineWidth(float width) in class PdfContentByte that should change it. However no matter what value I pass as its parameter the lines drawn are always extra thin. There is following line in javadoc of setLineWidth: The line width specifies the thickness of the line used to stroke a path and is measured in user space units. I don't know what is "space unit". Everything else in iText seems to be measured in point(around 1/72 inch). I cant find any reference to what are those "space units" and how to change them. code: to.setLineWidth(thickness); to.moveTo(x, y); to.lineTo(x + 100, y + 100); Variable to contains instance of PdfContentByte.

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• Help me with a solution for what could be solutioned by virtual static fields... in FPC

  - by Gregory Smith

  Hi I'm doing an event manager in Freepascal Each event is an object type TEvent (=object), each kind of event must derive from this class. Events are differentiated by an integer identificator, assigned dynamically. The problem is that i want to retrieve the event id of an instance, and i can't do it well. All instances of a class(object) have a unique id = so it should be static field. All classes have a diferent id = so it should be virtual. Event ids are assignated in run time, and can change = so it can't be a simple method In sum, I can't put all this together. I'm looking for an elegant solution, i don't want to write a hardcoded table, actualizing it in every constructor... etc, i'd prefer something taking advantage of the polymorphism Can anyone help me with another technical or design solution? I remark I don't want to use class instead of object construct.(property doesn't work on objects? :(

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• Java Logger with Servlets

  - by Sunny

  Hi Guys, I am using a wrapper class A which initializes the java.util.logger static class A { public static Logger logger; public static void init(){ logger = Logger.getLogger("test"); } Now, everywhere in my program I call A.init() and then logger.log("Message+uniqid"). But recently I moved to HTTP servlets and I am having problems. Basically, If a app is already running and the logger is logging... and someone else runs the app again, the logger from the previous instance stops and starts logging for the second one. Can anyone have a solution to how I should go about fixing this static variable issue? I can pass the logger into all constructor classes but thats really tedious. Any better solution would be appreciated..

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• boost pool_alloc

  - by mr grumpy

  Why is the boost::fast_pool_allocator built on top of a singleton pool, and not a separate pool per allocator instance? Or to put it another way, why only provide that, and not the option of having a pool per allocator? Would having that be a bad idea? I have a class that internally uses about 10 different boost::unordered_map types. If I'd used the std::allocator then all the memory would go back to the system when it called delete, whereas now I have to call release_memory on many different allocator types at some point. Would I be stupid to roll my own allocator that uses pool instead of singleton_pool? thanks

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• Entity framework and many to many queries unusable?

  - by John Landheer

  I'm trying EF out and I do a lot of filtering based on many to many relationships. For instance I have persons, locations and a personlocation table to link the two. I also have a role and personrole table. EDIT: Tables: Person (personid, name) Personlocation (personid, locationid) Location (locationid, description) Personrole (personid, roleid) Role (roleid, description) EF will give me persons, roles and location entities. EDIT: Since EF will NOT generate the personlocation and personrole entity types, they cannot be used in the query. How do I create a query to give me all the persons of a given location with a given role? In SQL the query would be select p.* from persons as p join personlocations as pl on p.personid=pl.personid join locations as l on pl.locationid=l.locationid join personroles as pr on p.personid=pr.personid join roles as r on pr.roleid=r.roleid where r.description='Student' and l.description='Amsterdam' I've looked, but I can't seem to find a simple solution.

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• Navigate touch-tone menus via modem

  - by Kongress

  I have a system that I need to programmatically interface with that requires a set of numbers to be dialed after the phone line is picked up, like a standard automated phone answering system. For instance, dial the number 123-456-7890, wait for the line to be answered, wait 15 seconds for the voice prompt, dial 1234#, hang up. The question is, can I and how do I do that through a modem? I know how to dial a number through a modem, it's simply ATDT[phone number], but that will attempt to initiate a data connection which will not allow touch-tone number entry. Would a voice modem provide the necessary capability? If so, could anyone provide example commands to accomplish this?

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• Access violation of member of pointer object

  - by Martin Lauridsen

  So I am coding this client/server program. This code is from the client side. The client has an instance of an object mpqs_sieve *instance_; The reason I make it as a pointer is, that mpqs_sieve only has a constructor that takes 3 arguments, and I want to instantiate it at a later point in time. The client first gets some data from the server, and uses this to instantiate instance_. After this, it will request some more data, and upon receiving this (these are three coeffecients for a quadratic polynomial), it should set these in the instance_ object. However upon calling a member function of instance_, I get an access violation on one of the members of instance_ within that function call. I posted my code here: on pastebin, and I get the error on line 100. The call comes from line 71, and before that line 21. Any ideas to solve this? Thanks!

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• Borland Starteam incorrect files status

  - by Kate

  I have some project saved in starteam. As there are a lot of obsolete files I can't check in or check out all project, only changed files. Now I copy project from one computer to another for other developer. I expect starteam treats copied project as new item for check in and check out, but it don't. Forexample: I modified file on fist computer. I update list of files on second computer and see this file in "check in" list, as I modified it on second computer. It is inncorrect. I think there is some configuration file or something like, that saves computer (or user) settings. So when project is copied, settings is copied too. Do anybody know how to change this configuration to set copied project as new instance of starteam???

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• opengl invert framebuffer pixels

  - by ToxIk

  I was wondering was the best way to invert the color pixels in the frame buffer is. I know it's possible to do with glReadPixels() and glDrawPixels() but the performance hit of those calls is pretty big. Basically, what I'm trying to do is have an inverted color cross-hair which is always visible no matter what's behind it. For instance, I'd have an arbitrary alpha mask bitmap or texture, have it render without depth test after the scene is drawn, and all the frame buffer pixels under the masked (full alpha) pixels of the texture would be inverted. I've been trying to do this with a texture, but I'm getting some strange results, also all the blending options I still find confusing.

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• Change NSNumber value by allocating new NSNumber?

  - by Peter Hajas

  I understand that NSNumber is immutable, but I still have the need to change it in my app. I use it because it's an object, and therefore usable with @property (if I could, I would use float or CGFloat in a heartbeat, but sadly, I can't). Is there any way to just overwrite the old NSNumber instance? I'm trying this: NSNumber *zero = [[NSNumber alloc] initWithFloat:0.0]; myNSNumber = zero but this doesn't change the value. This is a simplified version of my code, as I'm changing the root view controller's parameter (I know, not MVC-friendly). Still, the changing of the value should be the same assignment, right? Should I release myNSNumber first? What should I set the @property at for myNSNumber? Thanks!

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• Does a Collection<T> wrap an IList<T> or enumerate over the IList<T>?

  - by Brian Triplett

  If I am exposing a internal member via a Collection property via: public Collection<T> Entries { get { return new Collection<T>(this.fieldImplimentingIList<T>); } } When this property is called what happens? For example what happens when the following lines of code are called: T test = instanceOfAbove.Entries[i]; instanceOfAbove[i] = valueOfTypeT; It's clear that each time this property is called a new reference type is created but what acctually happens? Does it simply wrap the IList<T> underneath, does it enumerate over the IList<T> and to create a new Collection<T> instance? I'm concerned about performance if this property is used in a for loop.

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