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• Treebeard admin in Django

  - by Sharath

  I've setup Treebeard in Django and everything seems to have gone well. I tried to setup the admin system and I can see my models being presented in the admin interface. However, when I try to add new data using the admin interface, I get the following error in my template. The code still works fine, and I did a check in my DB and the data seems to be inserted properly. However, the view doesn't seem to load properly. Any idea about what is causing this?? The exception am getting is.. Caught an exception while rendering: Failed lookup for key [request] in u'[{\'action_index\': 0, \'block\': , , , , , , ]}, {\'block\': , , , ], , , , , \n \', ], , ], , , , ], , , \n \', , , , , , , , , ], , ], \n \']}, {\'cl\': , \'root_path\': None, \'actions_on_bottom\': False, \'title\': u\'Select album to change\', \'has_add_permission\': True, \'media\': , \'is_popup\': False, \'action_form\': , \'actions_on_top\': True, \'app_label\': \'gallery\'}, {\'MEDIA_URL\': \'\'}, {\'LANGUAGES\': ((\'ar\', \'Arabic\'), (\'bn\', \'Bengali\'), (\'bg\', \'Bulgarian\'), (\'ca\', \'Catalan\'), (\'cs\', \'Czech\'), (\'cy\', \'Welsh\'), (\'da\', \'Danish\'), (\'de\', \'German\'), (\'el\', \'Greek\'), (\'en\', \'English\'), (\'es\', \'Spanish\'), (\'et\', \'Estonian\'), (\'es-ar\', \'Argentinean Spanish\'), (\'eu\', \'Basque\'), (\'fa\', \'Persian\'), (\'fi\', \'Finnish\'), (\'fr\', \'French\'), (\'ga\', \'Irish\'), (\'gl\', \'Galician\'), (\'hu\', \'Hungarian\'), (\'he\', \'Hebrew\'), (\'hi\', \'Hindi\'), (\'hr\', \'Croatian\'), (\'is\', \'Icelandic\'), (\'it\', \'Italian\'), (\'ja\', \'Japanese\'), (\'ka\', \'Georgian\'), (\'ko\', \'Korean\'), (\'km\', \'Khmer\'), (\'kn\', \'Kannada\'), (\'lv\', \'Latvian\'), (\'lt\', \'Lithuanian\'), (\'mk\', \'Macedonian\'), (\'nl\', \'Dutch\'), (\'no\', \'Norwegian\'), (\'pl\', \'Polish\'), (\'pt\', \'Portuguese\'), (\'pt-br\', \'Brazilian Portuguese\'), (\'ro\', \'Romanian\'), (\'ru\', \'Russian\'), (\'sk\', \'Slovak\'), (\'sl\', \'Slovenian\'), (\'sr\', \'Serbian\'), (\'sv\', \'Swedish\'), (\'ta\', \'Tamil\'), (\'te\', \'Telugu\'), (\'th\', \'Thai\'), (\'tr\', \'Turkish\'), (\'uk\', \'Ukrainian\'), (\'zh-cn\', \'Simplified Chinese\'), (\'zh-tw\', \'Traditional Chinese\')), \'LANGUAGE_BIDI\': False, \'LANGUAGE_CODE\': \'en-us\'}, {}, {\'perms\': , \'messages\': [], \'user\': }, {}]' This happens after I hit the save button in Django admin. This is my admin.py implementation.. class MP_Album_Admin(TreeAdmin): pass admin.site.register(Album,MP_Album_Admin)

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• Graph limitations - Should I use Decorator?

  - by Nick Wiggill

  I have a functional AdjacencyListGraph class that adheres to a defined interface GraphStructure. In order to layer limitations on this (eg. acyclic, non-null, unique vertex data etc.), I can see two possible routes, each making use of the GraphStructure interface: Create a single class ("ControlledGraph") that has a set of bitflags specifying various possible limitations. Handle all limitations in this class. Update the class if new limitation requirements become apparent. Use the decorator pattern (DI, essentially) to create a separate class implementation for each individual limitation that a client class may wish to use. The benefit here is that we are adhering to the Single Responsibility Principle. I would lean toward the latter, but by Jove!, I hate the decorator Pattern. It is the epitome of clutter, IMO. Truthfully it all depends on how many decorators might be applied in the worst case -- in mine so far, the count is seven (the number of discrete limitations I've recognised at this stage). The other problem with decorator is that I'm going to have to do interface method wrapping in every... single... decorator class. Bah. Which would you go for, if either? Or, if you can suggest some more elegant solution, that would be welcome. EDIT: It occurs to me that using the proposed ControlledGraph class with the strategy pattern may help here... some sort of template method / functors setup, with individual bits applying separate controls in the various graph-canonical interface methods. Or am I losing the plot?

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• EntityFramework repository template- how to write GetByID lamba within a template class?

  - by FerretallicA

  I am trying to write a generic one-size-fits-most repository pattern template class for an Entity Framework-based project I'm currently working on. The (heavily simplified) interface is: internal interface IRepository<T> where T : class { T GetByID(int id); IEnumerable<T> GetAll(); IEnumerable<T> Query(Func<T, bool> filter); } GetByID is proving to be the killer. In the implementation: public class Repository<T> : IRepository<T>,IUnitOfWork<T> where T : class { // etc... public T GetByID(int id) { return this.ObjectSet.Single<T>(t=>t.ID == id); } t=t.ID == id is the particular bit I'm struggling with. Is it even possible to write lamba functions like that within template classes where no class-specific information is going to be available?

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• validation properties by attribute

  - by netmajor

  I create class with two property - name,link(below). I use simple property validation by Required and StringLength attribute. I bind this class object to WPF ListBox(with textBoxs). But when I have textbox empty or write words longer than 8 sign nothing happens :/ What should I do to fires ErrorMessage? Or how to implement validation in other way ? I also try use : if (value is int) { throw new ArgumentException("Wpisales stringa!!"); } But it only fires in debug mode :/ My class with implementation of attribute validation: public class RssInfo : INotifyPropertyChanged { public RssInfo() { } public RssInfo(string _nazwa, string _link) { nazwa = _nazwa; link = _link; } private string nazwa; [Required(ErrorMessage = "To pole jest obowiazkowe nAZWA")] public string Nazwa { get { return nazwa; } set { if (value != nazwa) { nazwa = value; onPropertyChanged("Nazwa"); } if (value is int) { throw new ArgumentException("Wpisales stringa!!"); } } } private string link; [Required(ErrorMessage="To pole jest obowiazkowe link")] [StringLength(8, ErrorMessage = "Link cannot be longer than 8 characters")] public string Link { get { return link; } set { if (value != link) { link = value; onPropertyChanged("Link"); } } } #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; #endregion private void onPropertyChanged(string propertyName) { if (this.PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } }

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• Hibernate: order multiple one-to-many relations

  - by Markos Fragkakis

  I have a search screen, using JSF, JBoss Seam and Hibernate underneath. There are columns for A, B and C, where the relations are as follows: A (1< -- ) B (1< -- ) C A has a List< B and B has a List< C (both relations are one-to-many). The UI table supports ordering by any column (ASC or DESC), so I want the results of the query to be ordered. This is the reason I used Lists in the model. However, I got an exception that Hibernate cannot eagerly fetch multiple bags (it considers both lists to be bags). There is an interesting blog post here, and they identify the following solutions: Use @IndexColumn annotation (there is none in my DB, and what's more, I want the position of results to be determined by the ordering, not by an index column) Fetch lazily (for performance reasons, I need eager fetching) Change List to Set So, I changed the List to Set, which by the way is more correct, model-wise. First, if don't use @OrderBy, the PersistentSet returned by Hibernate wraps a HashSet, which has no ordering. Second, If I do use @OrderBy, the PersistentSet wraps a LinkedHashSet, which is what I would like, but the OrderBy property is hardcoded, so all other ordering I perform through the UI comes after it. I tried again with Sets, and used SortedSet (and its implementation, TreeSet), but I have some issues: I want ordering to take place in the DB, and not in-memory, which is what TreeSet does (either through a Comparator, or through the Comparable interface of the elements). Second, I found that there is the Hibernate annotation @Sort, which has a SortOrder.UNSORTED and you can also set a Comparator. I still haven't managed to make it compile, but I am still not convinced it is what I need. Any advice?

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• iPhone - User Defaults and UIImages

  - by Staros

  Hello, I've been developing an iPhone app for the last few months. Recently I wanted to up performance and cache a few of the images that are used in the UI. The images are downloaded randomly from the web by the user so I can't add specific images to the project. I'm also already using NSUserDefaults to save other info within the app. So now I'm attempting to save a dictionary of UIImages to my NSUserDefaults object and get... -[UIImage encodeWithCoder:]: unrecognized selector sent to instance I then decided to subclass UIImage with a class named UISaveableImage and implement NSCoding. So now I'm at... @implementation UISaveableImage -(void)encodeWithCoder:(NSCoder *)encoder { [encoder encodeObject:super forKey:@"image"]; } -(id)initWithCoder:(NSCoder *)decoder { if (self=[super init]){ super = [decoder decodeObjectForKey:@"image"]; } return self; } @end which isn't any better than where I started. If I was able to convert an UIImage to NSData I would be good, but all I can find are function like UIImagePNGRepresentation which require me to know what type of image this was. Something that UIImage doesn't allow me to do. Thoughts? I feel like I might have wandered down the wrong path...

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• .NET Membership with Repository Pattern

  - by Zac

  My team is in the process of designing a domain model which will hide various different data sources behind a unified repository abstraction. One of the main drivers for this approach is the very high probability that these data sources will undergo significant change in the near future and we don't want to be re-writing business logic when this happens. One data source will be our membership database which was originally implemented using the default ASP.Net Membership Provider. The membership provider is tied to the System.Web.Security namespace but we have a design guideline requiring that our domain model layer is not dependent upon System.Web (or any other implementation/environment dependency) as it will be consumed in different environments - nor do we want our websites directly communicating with databases. I am considering what would be a good approach to reconciling the MembershipProvider approach with our abstracted n-tier architecture. My initial feeling is that we could create a "DomainMembershipProvider" which interacts with the domain model and then implement objects in the model which deal with the repository and handle validation/business logic. The repository would then implement data access using our (as-yet undecided) ORM/data access tool. Are there are any glaring holes in this approach - I haven't worked closely with the MembershipProvider class so may well be missing something. Alternatively, is there an approach that you think will better serve the requirements I described above? Thanks in advance for your thoughts and advice. Regards, Zac

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• Custom SSL handling stopped working on Android 2.2 FroYo

  - by Eric

  For my app, Transdroid, I am connecting to remote servers via HTTP and optionally securely via HTTPS. For these HTTPS connections with the HttpClient I am using a custom SSL socket factory implementation to make sure self-signed certificates are working. Basically, I accept everything and ignore every checking of any certificate. This has been working fine for some time now, but it no longer work for Android 2.2 FroYo. When trying to connect, it will return an exception: java.io.IOException: SSL handshake failure: I/O error during system call, Broken pipe Here is how I initialize the HttpClient: SchemeRegistry registry = new SchemeRegistry(); registry.register(new Scheme("http", new PlainSocketFactory(), 80)); registry.register(new Scheme("https", (trustAll ? new FakeSocketFactory() : SSLSocketFactory.getSocketFactory()), 443)); client = new DefaultHttpClient(new ThreadSafeClientConnManager(httpParams, registry), httpParams); I make use of a FakeSocketFactory and FakeTrustManager, of which the source can be found here: http://code.google.com/p/transdroid/source/browse/#svn/trunk/src/org/transdroid/util Again, I don't understand why it suddenly stopped work, or even what the error 'Broken pipe' means. I have seen messages on Twitter that Seesmic and Twidroid fail with SSL enabled on FroYo as well, but am unsure if it's related. Thanks for any directions/help!

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• Launching a modal UINavigationController

  - by Alexi Groove

  I'd like to launch a modal view controller the way one does with 'ABPeoplePickerNavigationController' and that is without having to creating a navigation controller containing the view controller. Doing something similar yields a blank screen with no title for the navigation bar and there's no associated nib file loaded for the view even though I am invoking the initWithNibName when the 'init' is called. My controller looks like: @interface MyViewController : UINavigationController @implementation MyViewController - (id)init { NSLog(@"MyViewController init invoked"); if (self = [super initWithNibName:@"DetailView" bundle:nil]) { self.title = @"All Things"; } return self; } - (void)viewDidLoad { [super viewDidLoad]; self.title = @"All Things - 2"; } @end When using the AB controller, all you do is: ABPeoplePickerNavigationController *picker = [[ABPeoplePickerNavigationController alloc] init]; picker.peoplePickerDelegate = self; [self presentModalViewController:picker animated:YES]; [picker release]; ABPeoplePickerNavigationController is declared as: @interface ABPeoplePickerNavigationController : UINavigationController The other way to create a modal view as suggested in Apple's 'View Controller Programming Guide for iPhone OS': // Create a regular view controller. MyViewController *modalViewController = [[[MyViewController alloc] initWithNibName:nil bundle:nil] autorelease]; // Create a navigation controller containing the view controller. UINavigationController *secondNavigationController = [[UINavigationController alloc] initWithRootViewController:modalViewController]; // Present the navigation controller as a modal view controller on top of an existing navigation controller [self presentModalViewController:secondNavigationController animated:YES]; I can create it this way fine (as long as I change the MyViewController to inherit from UIViewController instead of UINavigationController). What else should I be doing to MyViewController to launch the same way as ABPeoplePickerNavigationController?

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• Unable to call RESTful web services methods

  - by Alessandro

  Hello, I'm trying to dive into the RESTful web services world and have started with the following template: [ServiceContract] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)] public class Test { // TODO: Implement the collection resource that will contain the SampleItem instances [WebGet(UriTemplate = ""), OperationContract] public List<SampleItem> GetCollection() { // TODO: Replace the current implementation to return a collection of SampleItem instances return new List<SampleItem>() {new SampleItem() {Id = 1, StringValue = "Hello"}}; } [WebInvoke(UriTemplate = "", Method = "POST"), OperationContract] public SampleItem Create(SampleItem instance) { // TODO: Add the new instance of SampleItem to the collection throw new NotImplementedException(); } [WebGet(UriTemplate = "{id}"), OperationContract] public SampleItem Get(string id) { // TODO: Return the instance of SampleItem with the given id throw new NotImplementedException(); } [WebInvoke(UriTemplate = "{id}", Method = "PUT"), OperationContract] public SampleItem Update(string id, SampleItem instance) { return new SampleItem { Id = 99, StringValue = "Done" }; } [WebInvoke(UriTemplate = "{id}", Method = "DELETE"), OperationContract] public void Delete(string id) { // TODO: Remove the instance of SampleItem with the given id from the collection throw new NotImplementedException(); } } I am able to perform the GET operation but I am unable to perform PUT, POST or DELETE requests. Can anyone explain me how to perform these operations and how to create the correct URLs? Best regards Alessandro

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• Twitter4J throws exception in TwitterFactory

  - by Philipp Andre

  Hello Guys, i'm trying to access twitter via oauth. Therefore, i registered my app, downloaded Twitter4j, added the jars in my Eclipse-Project, and then tried to execute the following code: Twitter twitter = new TwitterFactory().getOAuthAuthorizedInstance("[key]","[secretKey]); RequestToken requestToken = twitter.getOAuthRequestToken(); System.out.println(requestToken.getAuthorizationURL()); But it raises the following exception: [Sat May 29 11:19:11 CEST 2010]Using class twitter4j.internal.logging.StdOutLoggerFactory as logging factory. [Sat May 29 11:19:11 CEST 2010]Use twitter4j.internal.http.alternative.HttpClientImpl as HttpClient implementation. Exception in thread "main" java.lang.AssertionError: java.lang.reflect.InvocationTargetException at twitter4j.internal.http.HttpClientFactory.getInstance(HttpClientFactory.java:71) at twitter4j.internal.http.HttpClientWrapper.<init>(HttpClientWrapper.java:59) at twitter4j.http.OAuthAuthorization.init(OAuthAuthorization.java:83) at twitter4j.http.OAuthAuthorization.<init>(OAuthAuthorization.java:74) at twitter4j.TwitterFactory.getOAuthAuthorizedInstance(TwitterFactory.java:112) at MainProgram.main(MainProgram.java:18) Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at twitter4j.internal.http.HttpClientFactory.getInstance(HttpClientFactory.java:65) ... 5 more Caused by: java.lang.NoClassDefFoundError: org/apache/http/impl/client/DefaultHttpClient at twitter4j.internal.http.alternative.HttpClientImpl.<init>(HttpClientImpl.java:63) ... 10 more I currently can't figure out why ... can you please give me some suggestions? Best regards Philipp

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• MFMailComposeViewController hangs my app

  - by Neal L

  Hi, I am trying to add email functionality to my app. I can get the MFMailComposeViewController to display correctly and pre-populate its subject and body, but for some reason when the user clicks on the "Cancel" or "Send" buttons in the nav bar the app just hangs. I inserted a NSLog() statement into the first line of mailComposeController"didFinishWithResult:error and it doesn't even print that line out to the console. Does anybody have an idea what would cause the MFMailComposeViewController to hang like that? Here is my code from the header: #import "ManagedObjectEditor.h" #import <MessageUI/MessageUI.h> @interface MyManagedObjectEditor : ManagedObjectEditor <MFMailComposeViewControllerDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate> { } - (IBAction)emailObject; @end from the implementation file: if ([MFMailComposeViewController canSendMail]) { MFMailComposeViewController *mailComposer = [[MFMailComposeViewController alloc] init]; mailComposer.delegate = self; [mailComposer setSubject:NSLocalizedString(@"An email from me", @"An email from me")]; [mailComposer setMessageBody:emailString isHTML:YES]; [self presentModalViewController:mailComposer animated:YES]; [mailComposer release]; } [error release]; [emailString release]; and here is the code from the callback: #pragma mark - #pragma mark Mail Compose Delegate Methods - (void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error { NSLog(@"in didFinishWithResult:"); switch (result) { case MFMailComposeResultCancelled: NSLog(@"cancelled"); break; case MFMailComposeResultSaved: NSLog(@"saved"); break; case MFMailComposeResultSent: NSLog(@"sent"); break; case MFMailComposeResultFailed: { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Error sending email!",@"Error sending email!") message:[error localizedDescription] delegate:nil cancelButtonTitle:NSLocalizedString(@"Bummer",@"Bummer") otherButtonTitles:nil]; [alert show]; [alert release]; break; } default: break; } [self dismissModalViewControllerAnimated:YES]; } Thanks!

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• Reliable strtotime() result for different languages

  - by Maksee

  There was always a strange bug in Joomla when adding new article with back-end displayed with a language other than English (for me it's Russian). The field "Finish Publishing" started to be current date instead of "Never" equivalent in Russian. For a site in php4 finally found that strtotime function returns different results for arbitrary words. For "Never" it always -1 and joomla relies on this result in the JDate implementation. But in other case it sometimes returns a valid date. For russian translation of Never (???????) it is the case, but also for single "N" it is the case, so if one decided to change the string to some other he or she would face the same issue. So the code below <?php echo "Res:".strtotime("N")."<br>"; echo "Res:".strtotime("Nev")."<br>"; echo "Res:".strtotime("Neve")."<br>"; echo "Res:".strtotime("Never")."<br>"; ?> Outputs: Res:1271120400 Res:-1 Res:-1 Res:-1 So what are the solutions would be in this case? I would like not to write language-specific date.php handler, but to modify date method of JDate class, but what are language-neutral changes would be in order to detect invalid string. Thank you

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• Is android's motion event handling accurate??

  - by Peterdk

  Bug I have a weird bug in my piano app. Sometimes keys (and thus notes) hang. I did a lot of debugging and narrowed it down to what looks like androids inaccuracy of motion event handling: DEBUG/(2091): ACTION_DOWN A4 DEBUG/(2091): KeyDown: A4 DEBUG/(2091): ACTION_MOVE A4 => A4 DEBUG/(2091): ACTION_MOVE ignoring DEBUG/(2091): ACTION_MOVE A4 => A4 DEBUG/(2091): ACTION_MOVE ignoring DEBUG/(2091): ACTION_MOVE A4 => A4 DEBUG/(2091): ACTION_MOVE ignoring DEBUG/(2091): ACTION_UP B4 //HOW CAN THIS BE???? DEBUG/(2091): KeyUp: B4 DEBUG/(2091): Stream is null, can't stop DEBUG/(2091): Hanging Note: A4 X=240-287 EventX=292 Y=117-200 EventY=164 DEBUG/(2091): KeyUp Note: B4 X=288-335 EventX=292 Y=117-200 EventY=164 Clearly it can be seen here that out of nowhere I suddenly have an ACTION_UP for another note. Shouldn't I definitely get a ACTION_MOVE first? As shown in the end of the log, it's definitely not an error in region detection, since the ACTION_UP event is clearly in the B4 region. Logging Implementation details Every onTouchEvent() call is logged, so the log is accurate. The relevant pseudo-code for the ACTION_MOVE logging is: Key oldKey = Key.get(event.getHistoricalX(), event.getHistoricalY()); Key newKey = Key.get(event.getX(), event.getY()); Question Is this normal behaviour for Android (the jumping in coordinates)? Am I missing something?

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• Is there any way to access files in your source tree in Android?

  - by Chris Thompson

  Hi all, This is a bit unorthodox but I'm trying to figure out if there's a way to access files stored in the src tree of my applications apk in Android. I'm trying to use i-Jetty (Jetty implementation for Android) and rather than use it as a separate application and manually download my war file, I'd rather just bake i-jetty in. However, in order to use (easily) standard html/jsp I need to be able to give it a document root, preferably within my application's apk file. I know Android specifically works to prevent you from accessing (freely) the stuff on the actual system so this may not be possible, but I'm thinking it might be possible to access something within the apk. One option to work around this would be to have all of the files stored in the res directory and then copy them to the sdcard on startup but this wouldn't allow me to automatically remove the files on uninstall. To give you an idea of what I've tried, currently, the html files are stored in org.webtext.android Context rootContext = new Context(server_, "/", Context.SESSIONS); rootContext.setResourceBase("org/webtext/webapp"); Returns a 404 error. final URL url = this.getClassLoader().getResource("org/webtext/webapp"); Context html = new WebAppContext(url.toExternalForm(), "/"); Blows up with a NullPointerException because no URL is returned from the getResource call. Any thoughts would be greatly appreciated! Thanks, Chris

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• How do I read the manifest file for a webapp running in apache tomcat?

  - by Nik Reiman

  I have a webapp which contains a manifest file, in which I write the current version of my application during an ant build task. The manifest file is created correctly, but when I try to read it in during runtime, I get some strange side-effects. My code for reading in the manifest is something like this: InputStream manifestStream = Thread.currentThread() .getContextClassLoader() .getResourceAsStream("META-INFFFF/MANIFEST.MF"); try { Manifest manifest = new Manifest(manifestStream); Attributes attributes = manifest.getMainAttributes(); String impVersion = attributes.getValue("Implementation-Version"); mVersionString = impVersion; } catch(IOException ex) { logger.warn("Error while reading version: " + ex.getMessage()); } When I attach eclipse to tomcat, I see that the above code works, but it seems to get a different manifest file than the one I expected, which I can tell because the ant version and build timestamp are both different. Then, I put "META-INFFFF" in there, and the above code still works! This means that I'm reading some other manifest, not mine. I also tried this.getClass().getClassLoader().getResourceAsStream(...) But the result was the same. What's the proper way to read the manifest file from inside of a webapp running in tomcat? Edit: Thanks for the suggestions so far. Also, I should note that I am running tomcat standalone; I launch it from the command line, and then attach to the running instance in Eclipse's debugger. That shouldn't make a difference, should it?

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• "Work stealing" vs. "Work shrugging (tm)"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on a "work shrugging(tm)" as a load-balancing strategy? I am surprised because work-stealing seems to me to have an inherent weakness when implementating efficient fine-grained load-balancing. Vis:- Relying on consumer processors to implement distribution (by actively stealing) begs the question of what these processors do when they find no work? None of the work-stealing references and implementations I have come across so far address this issue satisfactorarily for me. They either:- 1) Manage not to disclose what they do with idle processors! [Cilk] (?anyone know?) 2) Have all idle processors sleep and wake periodically and scatter messages to the four winds to see if any work has arrived [e.g. JAWS] (= way too latent & inefficient for me). 3) Assume that it is acceptable to have processors "spinning" looking for work ( = non-starter for me!) Unless anyone thinks there is a solution for this I will move on to consider a "Work Shrugging(tm)" strategy. Having the task-producing processor distribute excess load seems to me inherently capable of a much more efficient implementation. However a quick google didn't show up anything under the heading of "Work Shrugging" so any pointers to prior-art would be welcome. tx Tags I would have added if I was allowed to [work-stealing]

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• How should I go about implementing a points-to analysis in Maude?

  - by reprogrammer

  I'm going to implement a points-to analysis algorithm. I'd like to implement this analysis mainly based on the algorithm by Whaley and Lam. Whaley and Lam use a BDD based implementation of Datalog to represent and compute the points-to analysis relations. The following lists some of the relations that are used in a typical points-to analysis. Note that D(w, z) :- A(w, x),B(x, y), C(y, z) means D(w, z) is true if A(w, x), B(x, y), and C(y, z) are all true. BDD is the data structure used to represent these relations. Relations input vP0 (variable : V, heap : H) input store (base : V, field : F, source : V) input load (base : V, field : F, dest : V) input assign (dest : V, source : V) output vP (variable : V, heap : H) output hP (base : H, field : F, target : H) Rules vP(v, h) :- vP0(v, h) vP(v1, h) :- assign(v1, v2), vP(v2, h) hP(h1, f,h2) :- store(v1, f, v2), vP(v1, h1), vP(v2, h2) vP(v2, h2) :- load(v1, f, v2), vP(v1, h1), hP(h1, f, h2) I need to understand if Maude is a good environment for implementing points-to analysis. I noticed that Maude uses a BDD library called BuDDy. But, it looks like that Maude uses BDDs for a different purpose, i.e. unification. So, I thought I might be able to use Maude instead of a Datalog engine to compute the relations of my points-to analysis. I assume Maude propagates independent information concurrently. And this concurrency could potentially make my points-to analysis faster than sequential processing of rules. But, I don't know the best way to represent my relations in Maude. Should I implement BDD in Maude myself, or Maude's internal unification based on BDD has the same effect?

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• Memory mapped files and "soft" page faults. Unavoidable?

  - by Robert Oschler

  I have two applications (processes) running under Windows XP that share data via a memory mapped file. Despite all my efforts to eliminate per iteration memory allocations, I still get about 10 soft page faults per data transfer. I've tried every flag there is in CreateFileMapping() and CreateFileView() and it still happens. I'm beginning to wonder if it's just the way memory mapped files work. If anyone there knows the O/S implementation details behind memory mapped files I would appreciate comments on the following theory: If two processes share a memory mapped file and one process writes to it while another reads it, then the O/S marks the pages written to as invalid. When the other process goes to read the memory areas that now belong to invalidated pages, this causes a soft page fault (by design) and the O/S knows to reload the invalidated page. Also, the number of soft page faults is therefore directly proportional to the size of the data write. My experiments seem to bear out the above theory. When I share data I write one contiguous block of data. In other words, the entire shared memory area is overwritten each time. If I make the block bigger the number of soft page faults goes up correspondingly. So, if my theory is true, there is nothing I can do to eliminate the soft page faults short of not using memory mapped files because that is how they work (using soft page faults to maintain page consistency). What is ironic is that I chose to use a memory mapped file instead of a TCP socket connection because I thought it would be more efficient. Note, if the soft page faults are harmless please note that. I've heard that at some point if the number is excessive, the system's performance can be marred. If soft page faults intrinsically are not significantly harmful then if anyone has any guidelines as to what number per second is "excessive" I'd like to hear that. Thanks.

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• python: how to design a container with elements that must reference their container

  - by Luke404

  (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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• TLS with SNI in Java clients

  - by ftrotter

  There is an ongoing discussion on the security and trust working group for NHIN Direct regarding the IP-to-domain mapping problem that is created with traditional SSL. If an HISP (as defined by NHIN Direct) wants to host thousands of NHIN Direct "Health Domains" for providers, then it will an "artificially inflated cost" to have to purchase an IP for each of those domains. Because Apache and OpenSSL have recently released TLS with support for the SNI extension, it is possible to use SNI as a solution to this problem on the server side. However, if we decide that we will allow server implementations of the NHINDirect transport layer to support TLS+SNI, then we must require that all clients support SNI too. OpenSSL based clients should do this by default and one could always us stunnel to implement an TLS+SNI aware client to proxy if your given programming language SSL implementation does not support SNI. It appears that native Java applications using OpenJDK do not yet support SNI, but I cannot get a straight answer out of that project. I know that there are OpenSSL Java libraries available but I have no idea if that would be considered viable. Can you give me a "state of the art" summary of where TLS+SNI support is for Java clients? I need a Java implementers perspective on this.

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• Big-O of PHP functions?

  - by Kendall Hopkins

  After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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• Autodetect Presence of CSV Headers in a File

  - by banzaimonkey

  Short question: How do I automatically detect whether a CSV file has headers in the first row? Details: I've written a small CSV parsing engine that places the data into an object that I can access as (approximately) an in-memory database. The original code was written to parse third-party CSV with a predictable format, but I'd like to be able to use this code more generally. I'm trying to figure out a reliable way to automatically detect the presence of CSV headers, so the script can decide whether to use the first row of the CSV file as keys / column names or start parsing data immediately. Since all I need is a boolean test, I could easily specify an argument after inspecting the CSV file myself, but I'd rather not have to (go go automation). I imagine I'd have to parse the first 3 to ? rows of the CSV file and look for a pattern of some sort to compare against the headers. I'm having nightmares of three particularly bad cases in which: The headers include numeric data for some reason The first few rows (or large portions of the CSV) are null There headers and data look too similar to tell them apart If I can get a "best guess" and have the parser fail with an error or spit out a warning if it can't decide, that's OK. If this is something that's going to be tremendously expensive in terms of time or computation (and take more time than it's supposed to save me) I'll happily scrap the idea and go back to working on "important things". I'm working with PHP, but this strikes me as more of an algorithmic / computational question than something that's implementation-specific. If there's a simple algorithm I can use, great. If you can point me to some relevant theory / discussion, that'd be great, too. If there's a giant library that does natural language processing or 300 different kinds of parsing, I'm not interested.

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• how to implement login and service features as in skype or msn chat in a wpf application

  - by black sensei

  Hello Good people! I'm building an WPF application that connect to web services for its operations.Things that i needed to be working are so far fine.Now i'll like to improve use experience by adding features like username editable combobox, sign me in when skype start and start when computer start. I have a fair idea about each feature but very small knowledge about their implementation. Question 1 username combobox : i use a combobox with isEditable set to true but i think it doesnt have the previous username, would that mean that i have to store every successful login username in a sqlite for example? Question 2 sign me in when skype start : i think about using sqlite after all to store the credentials and store the value (as in true or false) if autologin has to be performed. Question 3 start when computer start : i know it's about having is as service.but the process of using it as a service and removing its service when checkbox is checked or unckecked is a bit confusing to me. Question 4 Please wait(signing in) of skype if i want to do things like please wait at login(login is over webservice) in a WPF application should i use a animated gif in a grid that i can show when hiding the login combobox and passwordbox grid or i should use an animated object(for which i have no knowledge about for now) ? This post in mainly for you experts to either point me to the right resource and tell me what is done as best practice. things like dos and dons.Thanks for reading this and please let me have a clair idea about how to start implementing those features. thanks again

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• Vimeo Desktop App OAuth

  - by Barry

  Hi Guys, I'm currently having massive trouble with Vimeo's Oauth implementation and my desktop app. My program does the following correctly. 1- Requests a Unauthorized Request Token with my key and secret and returns - a Token and a Token secret. 2- Generates a URL for the user to go to using the token which then shows our application's name and allows the user to Authorize us to use his/her account. It then shows a verifier which the user returns and puts into our app. The problem is the third step and actually exchanging the tokens for the access tokens. Basically every time we try and get them we get a "Invalid / expired token - The oauth_token passed was either not valid or has expired" I looked at the documentation and there's supposed to be a callback to a server when deployed like that which gives the user an "authorized token" but as im developing a desktop app we can't do this. So I assume the token retrieved in 1 is valid for this step. (actually it seems it is: http://vimeo.com/forums/topic:22605) So I'm wondering now am I missing something here on my actual vimeo application account now? is it treating it as a web hosted app with callbacks? all the elements are there for this to work and I've used this same component to create a twitter Oauth login in exactly the same way and it was fine. Thanks in advance, Barry

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