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  • [Java] Safe way of exposing keySet().

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • Can I write a module/filter that gets fired before the web app get's run in Tomcat?

    - by Blankman
    Can I write a module/filter that gets put into the processing pipleline in Tomcat BEFORE the web application even gets run? Something that I could turn on/off for each web application that tomcat is handling. is this possible? So basically it would be a re-usable filter that hooks into the web pipeline that could alter the requests behavior or perform/modify the requests. One example would be to log all ip's, or redirect based on the url, block the request, etc.

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  • declerative_authorization on User problem

    - by Webpain
    I am trying to block all default methods except create and update in my users controller using declerative_authorization. But at the time I add filter_resource_access or filter_access_to into my usersController i always get "Couldn't find User without an ID". Anyone care to explain why this could be happening? class UsersController :new end end def show @user = @current_user end def edit @user = @current_user end def update @user = @current_user # makes our views "cleaner" and more consistent if @user.update_attributes(params[:user]) flash[:notice] = "Account updated!" redirect_to account_url else render :action = :edit end end end

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  • How do I create and read non-global variables that aren't destroyed at end of function?

    - by Paul Reilly
    I am attempting to code some plugins to use with MIDI sequencers but have hit a stumbling block. I can't use global-scope variables to store information because multiple instances of the .dll can exist which share memory. How do I create a class (for re-usability purposes in other plugins) containing 2 dimensional array and other variables the content of which is to be shared between functions? If that is possible, how would I read and write the data from the function in the framework where I do the processing?

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  • Elegant and 'correct' multiton implementation in Objective C?

    - by submachine
    Would you call this implementation of a multiton in objective-c 'elegant'? I have programmatically 'disallowed' use of alloc and allocWithZone: because the decision to allocate or not allocate memory needs to be done based on a key. I know for sure that I need to work with only two instances, so I'm using 'switch-case' instead of a map. #import "Multiton.h" static Multiton *firstInstance = nil; static Multiton *secondInstance = nil; @implementation Multiton + (Multiton *) sharedInstanceForDirection:(char)direction { return [[self allocWithKey:direction] init]; } + (id) allocWithKey:(char)key { return [self allocWithZone:nil andKey:key]; } + (id)allocWithZone:(NSZone *)zone andKey:(char)key { Multiton **sharedInstance; @synchronized(self) { switch (key) { case KEY_1: sharedInstance = &firstInstance; break; case KEY_2: sharedInstance = &secondInstance; break; default: [NSException raise:NSInvalidArgumentException format:@"Invalid key"]; break; } if (*sharedInstance == nil) *sharedInstance = [super allocWithZone:zone]; } return *sharedInstance; } + (id) allocWithZone:(NSZone *)zone { //Do not allow use of alloc and allocWithZone [NSException raise:NSObjectInaccessibleException format:@"Use allocWithZone:andKey: or allocWithKey:"]; return nil; } - (id) copyWithZone:(NSZone *)zone { return self; } - (id) retain { return self; } - (unsigned) retainCount { return NSUIntegerMax; } - (void) release { return; } - (id) autorelease { return self; } - (id) init { [super init]; return self; } PS: I've not tried out if this works as yet, but its compiling cleanly :)

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  • Does rails do a rollback if I use begin...rescue?

    - by codeman73
    I'd like to add a begin...rescue block to one of my controllers create method, in order to log better info and construct the correct error message to return to the client. Does the rescue in any way 'interrupt' the rollback process? I'm assuming rails automatically does a rollback. When does it happen? Has it already happened by the time I get in the rescue clause? I'm using mySQL on Dreamhost and I think they use innoDB.

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  • Java's Swing Threading

    - by nevets1219
    My understanding is that if I start up another thread to perform some actions, I would need to SwingUtilities.invokeAndWait or SwingUtilities.invokeLater to update the GUI while I'm in said thread. Please correct me if I'm wrong. What I'm trying to accomplish is relatively straightforward: when the user clicks submit, I want to (before performing any actions) disable the submit button, perform the action, and at the end of the action re-enable the button. My method to perform the action updates the GUI directly (displays results) when it gets the results back. This action basically queries a server and gets some results back. What I have so far is: boolean isRunning = false; synchronized handleButtonClick() { if ( isRunning == false ) { button.setEnabled( false ); isRunning = true; doAction(); } } doAction() { new Thread() { try { doAction(); // Concern A } catch ( ... ) { displayStackTrace( ... ); // Concern B } finally { SwingUtilities.invokeLater ( /* simple Runnable to enable button */ ); isRunning = false; } } } For both of my concerns above, do I would have to use SwingUtilities.invokeAndWait since they both will update the GUI? All GUI updates revolve around updating JTextPane. Do I need to in my thread check if I'm on EDT and if so I can call my code (regardless of whether it updates the GUI or not) and NOT use SwingUtilities.invokeAndWait?

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  • How is the default constructor of System.Drawing.Graphics removed?

    - by Albert Iordache
    When I try to create an object of Graphics, why doesn't the following work? System.Drawing.Graphics graphicsObj = new System.Drawing.Graphics(); (I am aware that I could create a private System.Windows.Forms.Panel Obj; and then do CreateGraphics() if I wanted it to work) I tried to find a custom constructor for Graphics, but I couldn't find one. Where did Microsoft define it, or how did it block it?

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  • Mapping the System.Exception with FaultException

    - by user357342
    I have used exception sheilding feature of application block, to map System.Exception with class that is marked as DataContract. It works very well. But When I have mapped the System.Exception with FaultException, I got the below error message. "An error has occurred while consuming this service. Please contact your administrator for more information. Error ID: fe2d28b5-8d26-430e-baf4-fe4b39da853c" Please let me know whether I can map the System.Exception with FaultException

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  • Linq to SQL: how get row security between write access??

    - by Francisco
    I would like to allow two threads to write in a table at the same time (I know the problem of updating the same row, but this would be a story apart). I need that in behalf of speed up the operations in my aplication (one thread could write in row X while another could do the same in row X+n instead of waiting the first to finalize). So, can I block rows instead of tables with Linq to SQL? Thanks.

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  • Secure WS client with UsernameToken(SOAP security header)

    - by user79163
    Hi, I'm trying to secure my WS client to be able to call the WS. My code looks like this: SendSmsService smsService = new SendSmsService(); SendSms sendSMS = smsService.getSendSms(); BindingProvider stub = (BindingProvider)sendSMS; //Override endpoint with local copy of wsdl. String URL ="";//here is the wsdl url Map<String,Object> requestContext = stub.getRequestContext(); requestContext.put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, URL); //Set usernametoken URL fileURL = loader.getResource("client-config.xml"); File file = new File(fileURL.getFile()); FileInputStream clientConfig = null; try { clientConfig = new FileInputStream(file); } catch (FileNotFoundException e) { e.printStackTrace(); } XWSSecurityConfiguration config = null; try { config = SecurityConfigurationFactory.newXWSSecurityConfiguration(clientConfig); } catch (Exception e) { e.printStackTrace(); log.warn("Exception: "+e.getMessage()); } requestContext.put(XWSSecurityConfiguration.MESSAGE_SECURITY_CONFIGURATION, config); //Invoke the web service String requestId = null; try { requestId = sendSMS.sendSms(addresses, senderName, charging, message, receiptRequest); } catch (PolicyException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ServiceException e) { // TODO Auto-generated catch block e.printStackTrace(); } and the config file looks like this: <xwss:JAXRPCSecurity xmlns:xwss="http://java.sun.com/xml/ns/xwss/config" optimize="true"> <xwss:Service> <xwss:SecurityConfiguration dumpMessages="true" xmlns:xwss="http://java.sun.com/xml/ns/xwss/config"> <xwss:UsernameToken name="username" password="password> </xwss:SecurityConfiguration> </xwss:Service> <xwss:SecurityEnvironmentHandler> util.SecurityEnvironmentHandler </xwss:SecurityEnvironmentHandler> </xwss:JAXRPCSecurity> The SecurityEnviromentHandler is a dummy class that implements javax.security.auth.callback.CallbackHandler. Authentication must be in compliance with Oasis Web Services Security Username Token Profile 1.0. But I'm constantly getting "Security header not valid" error. Where am I going wrong, can anyone tell me. I used wsimport(JAX_WS 2.1 to generate classes for my client) Note:Only thing I know about this WS is WSDL URL and user&pass for authentication

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  • Appending javascript code piece to end of the body tag

    - by uzay95
    I am looking for a way to insert javascript code block to end of ASP.NET page. Page.ClientScript.RegisterClientScriptBlock(typeof(Page), "showVideo", sScript, true); is appending to body but js codes are always requesting some js files didn't load or some functions are below of the script. How can i append scripts that i generated dynamically to the bottom of body? Thanks for your help.

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  • File upload fails when user is authenticated. Using IIS7 Integrated mode.

    - by Nikkelmann
    These are the user identities my website tells me that it uses: Logged on: NT AUTHORITY\NETWORK SERVICE (Can not write any files at all) and Not logged on: WSW32\IUSR_77 (Can write files to any folder) I have a ASP.NET 4.0 website on a shared hosting IIS7 web server running in Integrated mode with 32-bit applications support enabled and MSSQL 2008. Using classic mode is not an option since I need to secure some static files and I use Routing. In my web.config file I have set the following: <system.webServer> <modules runAllManagedModulesForAllRequests="true" /> </system.webServer> My hosting company says that Impersonation is enabled by default on machine level, so this is not something I can change. I asked their support and they referred me to this article: http://www.codinghub.net/2010/08/differences-between-integrated-mode-and.html Citing this part: Different windows identity in Forms authentication When Forms Authentication is used by an application and anonymous access is allowed, the Integrated mode identity differs from the Classic mode identity in the following ways: * ServerVariables["LOGON_USER"] is filled. * Request.LogognUserIdentity uses the credentials of the [NT AUTHORITY\NETWORK SERVICE] account instead of the [NT AUTHORITY\INTERNET USER] account. This behavior occurs because authentication is performed in a single stage in Integrated mode. Conversely, in Classic mode, authentication occurs first with IIS 7.0 using anonymous access, and then with ASP.NET using Forms authentication. Thus, the result of the authentication is always a single user-- the Forms authentication user. AUTH_USER/LOGON_USER returns this same user because the Forms authentication user credentials are synchronized between IIS 7.0 and ASP.NET. A side effect is that LOGON_USER, HttpRequest.LogonUserIdentity, and impersonation no longer can access the Anonymous user credentials that IIS 7.0 would have authenticated by using Classic mode. How do I set up my website so that it can use the proper identity with the proper permissions? I've looked high and low for any answers regarding this specific problem, but found nil so far... I hope you can help!

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  • Beginner += in Ruby

    - by WANNABE
    Looking at this block, I can follow the whole program until I hit, sum += square. What is he point of this line, what does it say??? sum = 0 [1, 2, 3, 4].each do |value| square = value * value sum += square end puts sum

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  • Do the 'up to date' guarantees provided by final field in Java's memory model extend to indirect ref

    - by mattbh
    The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed?

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  • how to made a "admin-only" for in html page (not view.py),has this method :user.is_superuser ??

    - by zjm1126
    in views.py: @user_passes_test(lambda u: u.is_superuser) def h_view(request): return render_to_response('mytest/news.html',context_instance=RequestContext(request)) but i want to show this page when admin login,and my now page is : <li id="tab_mytest"><a href="{% url mytest_list %}" class="{% block mytest_css_name %}{% endblock %}">{% trans "mytest" %}</a></li> how to change it, has this method :user.is_superuser ?? thanks

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  • How do I center this CSS?

    - by sarthaksss
    Here is the CSS - #slider ul, #slider li, #slider2 ul, #slider2 li{ margin:0; padding:0; list-style:none; } #slider2{margin-top:1em;} #slider li, #slider2 li{ /* define width and height of list item (slide) entire slider area will adjust according to the parameters provided here */ width:500px; height:250px; overflow:hidden; } #prevBtn, #nextBtn, #slider1next, #slider1prev{ display:block; width:30px; height:77px; position:absolute; left:-30px; top:71px; z-index:1000; } #nextBtn, #slider1next{ left:696px; } #prevBtn a, #nextBtn a, #slider1next a, #slider1prev a{ display:block; position:relative; width:30px; height:77px; background:url(../images/btn_prev.gif) no-repeat 0 0; } #nextBtn a, #slider1next a{ background:url(../images/btn_next.gif) no-repeat 0 0; } /* numeric controls */ #slider img{ width:500px; height:300px; } ol#controls{ margin:1em 0; padding:0; height:28px; } ol#controls li{ margin:0 10px 0 0; padding:0; float:left; list-style:none; height:28px; line-height:28px; } ol#controls li a{ float:left; height:28px; line-height:28px; border:1px solid #ccc; background:#b32d45; color:white; padding:0 10px; text-decoration:none; } ol#controls li.current a{ background:#5DC9E1; color:#fff; } ol#controls li a:focus, #prevBtn a:focus, #nextBtn a:focus{outline:none;} I want to center the #slider HTML <div id="slider"> <ul> <li>IMAGE</li> <li>IMAGE2</li> </ul> </div>

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  • Modal Popup Extender panel height width

    - by harold-sota
    I have a ajax asp.net modalpopupextender, I wont when I desplay popup, the popup cover all the browser window. The popup display a panel ane is inside the form not other container. My .aspx code is: < asp:Panel ID="OptionPanel" runat="server" CssClass="mp" Style="display: block; width:100%; height:100%" But don't work!!! Any ideas????

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  • Easy way to keep counting up infinitely

    - by Andrew Alexander
    What's a good way to keep counting up infinitely? I'm trying to write a condition that will keep going until there's no value in a database, so it's going to iterate from 0, up to theoretically infinity (inside a try block, of course). How would I count upwards infinitely? Or should I use something else? I am looking for something similar to i++ in other languages, where it keeps iterating until failure.

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  • Create jquery dropdown like RDP Menu Bar

    - by user51701
    I'm not all that familiar with jquery so I'm not quite sure how to do this. Basically, I want a block of html to stay hidden at the top of the page with a ~3px edge sticking out (something to mouseover), and when you mouse over it, the hidden section slides down. Basically I want it to work like the RDP full screen menu bar works. Any thoughts on what the best way of doing this is?

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  • Best (Java) book for understanding 'under the bonnet' for programming?

    - by Ben
    What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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  • Configure lua prosody for localhost only

    - by Alfred
    I want to use prosody or maybe another xmpp server to test my xmpp bot. I want it to only accept connection from the address/localhost(don't want to configure firewall to block access). I would like to know the easiest way to accomplish this.

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  • Wait between tasks with SingleThreadExecutor

    - by Lord.Quackstar
    I am trying to (simply) make a blocking thread queue, where when a task is submitted the method waits until its finished executing. The hard part though is the wait. Here's my 12:30 AM code that I think is overkill: public void sendMsg(final BotMessage msg) { try { Future task; synchronized(msgQueue) { task = msgQueue.submit(new Runnable() { public void run() { sendRawLine("PRIVMSG " + msg.channel + " :" + msg.message); } }); //Add a seperate wait so next runnable doesn't get executed yet but //above one unblocks msgQueue.submit(new Runnable() { public void run() { try { Thread.sleep(Controller.msgWait); } catch (InterruptedException e) { log.error("Wait to send message interupted", e); } } }); } //Block until done task.get(); } catch (ExecutionException e) { log.error("Couldn't schedule send message to be executed", e); } catch (InterruptedException e) { log.error("Wait to send message interupted", e); } } As you can see, there's alot of extra code there just to make it wait 1.7 seconds between tasks. Is there an easier and cleaner solution out there or is this it?

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