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• Accessing global variable in multithreaded Tomcat server

  - by jwegan

  I have a singleton object that I construct like thus: private static volatile KeyMapper mapper = null; public static KeyMapper getMapper() { if(mapper == null) { synchronized(Utils.class) { if(mapper == null) { mapper = new LocalMemoryMapper(); } } } return mapper; } The class KeyMapper is basically a synchronized wrapper to HashMap with only two functions, one to add a mapping and one to remove a mapping. When running in Tomcat 6.24 on my 32bit Windows machine everything works fine. However when running on a 64 bit Linux machine (CentOS 5.4 with OpenJDK 1.6.0-b09) I add one mapping and print out the size of the HashMap used by KeyMapper to verify the mapping got added (i.e. verify size = 1). Then I try to retrieve the mapping with another request and I keep getting null and when I checked the size of the HashMap it was 0. I'm confident the mapping isn't accidentally being removed since I've commented out all calls to remove (and I don't use clear or any other mutators, just get and put). The requests are going through Tomcat 6.24 (configured to use 200 threads with a minimum of 4 threads) and I passed -Xnoclassgc to the jvm to ensure the class isn't inadvertently getting garbage collected (jvm is also running in -server mode). I also added a finalize method to KeyMapper to print to stderr if it ever gets garbage collected to verify that it wasn't being garbage collected. I'm at my wits end and I can't figure out why one minute the entry in HashMap is there and the next it isn't :(

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• How can I implement an interface member in protected ?

  - by Nicolas Dorier

  Hi, I've been quite surprise when I saw the metadata of ReadOnlyObservableCollection in VS 2008... public class ReadOnlyObservableCollection<T> : ReadOnlyCollection<T>, INotifyCollectionChanged, INotifyPropertyChanged { // Summary: // Initializes a new instance of the System.Collections.ObjectModel.ReadOnlyObservableCollection<T> // class that serves as a wrapper for the specified System.Collections.ObjectModel.ObservableCollection<T>. // // Parameters: // list: // The collection to wrap. public ReadOnlyObservableCollection(ObservableCollection<T> list); // Summary: // Occurs when an item is added or removed. protected virtual event NotifyCollectionChangedEventHandler CollectionChanged; // // Summary: // Occurs when a property value changes. protected virtual event PropertyChangedEventHandler PropertyChanged; // Summary: // Raises the System.Collections.ObjectModel.ReadOnlyObservableCollection<T>.CollectionChanged // event. // // Parameters: // args: // The event data. protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs args); // // Summary: // Raises the System.Collections.ObjectModel.ReadOnlyObservableCollection<T>.PropertyChanged // event. // // Parameters: // args: // The event data. protected virtual void OnPropertyChanged(PropertyChangedEventArgs args); } As you can see, CollectionChanged, a member of INotifyCollectionChanged is implemented in protected... and I can't do that in my own class. .NET framework should not compile ! Does someone has an explanation of this mystery ?

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• When NOT TO USE 'this' keyword?

  - by LifeH2O

  Sorry for asking it again, there are already 3 questions about this keyword. But all of them tell the purpose of 'this'. My question is when not to use 'this' keyword . OR Is it all right to use this keyword always in situation like the code class RssReader { private XmlTextReader _rssReader; private XmlDocument _rssDoc; private XmlNodeList _xn; protected XmlNodeList Item { get { return _xn; } } public int Count { get { return _count; } } public bool FetchFeed(String url) { this._rssReader = new XmlTextReader(url); this._rssDoc = new XmlDocument(); _rssDoc.Load(_rssReader); _xn = _rssDoc.SelectNodes("/rss/channel/item"); _count = _xn.Count; return true; } } here i have not used 'this' with "_xn" and "_count" also not with "_rssDoc.Load(_rssReader);" is it fine? Should i use "this" with all occurrences of class variables within the class?

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• Passing params in rails... Breakthrough in understanding params, aka, the "aha" moment

  - by Brian McDonough

  I have a simple has_many belongs_to relationship and I want to include the parent object for the view of the belongs_to model and I have had some success, but I want it to work better. class Submission < ActiveRecord::Base belongs_to :user belongs_to :contest end class Contest < ActiveRecord::Base belongs_to :user has_many :submissions, :dependent => :destroy end In the case that works, I pass contest_id to submissions by placing it in the url: <%= link_to 'Submit Contest Entry', new_submission_path(:contest_id => @contest.id), :class => 'btn btn-primary btn-large mleft10' %> So that, combined with a hidden_field: <%= f.hidden_field :contest_id %> And a find_contest method in the controller (called with a before_filter): def find_contest #the next line is giving the error (line 76) @contest = Contest.find(params[:submission][:contest_id]) end Makes it work for submissions/new, but how do I add a find to the controller that just works across more than that one page, like if I want to access in show and index. Right now, I get an error: Started GET "/submissions?contest_id=5" for 127.0.0.1 at 2012-12-01 16:01:45 -0800 Processing by SubmissionsController#index as HTML Parameters: {"contest_id"=>"5"} User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 2 ORDER BY users.created_at DESC LIMIT 1 Completed 500 Internal Server Error in 37ms NoMethodError (undefined method `[]' for nil:NilClass): app/controllers/submissions_controller.rb:76:in `find_contest' [edited] Adding show action for submissions: before_filter :find_contest, :except => [:index, :show, :edit, :update, :destroy] def find_contest @contest = Contest.find(params[:submission][:contest_id]) end def show contest_id = @submission.contest_id @submission = @commentable = Submission.find(params[:id]) @comments = @commentable.comments.order(:created_at).reverse respond_to do |format| format.html # show.html.erb format.json { render :json => @submission } end end

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• Java/JAXB: Accessing property of object in a list

  - by Mark Lewis

  Hello Using JAXB I've created a series of classes which represent my XML schema. Validating against the schema an XML file has thus become a 'tree' of java objects representing the XML. Now I'd like to access, delete and add an object of one the created types in my tree. If I've got classes' methods arranged like this: RootType class has: public List<FQType> getFq() { // and setter return fq; } FQType class has: public RemapType getRemap() { // and setter return remap; } RemapType class has: public String getSource() { // and setter return source; } What's the most concise way to code reading and writing of the 'source' member of a RemapType instance in an FQType instance with, say, fqtypeID=1, in an array of type RootType (in which RootType instances also each have rootID)? Currently I'm using a for loop Iterator in which is an if rootID = mySelectedRootID. In the if I nest a second for loop Iterator over the contained FQType instances and in that a second if fqTypeID = mySelectedFQTypeID. IE for loop iterator/if statement pairs to recognise the object of desire. With all the bells and whistles this way is nearly 15 lines of code to access a data type - can I do this in one line? Thanks

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• How to create an instance of object with RTTI in Delphi 2010?

  - by Paul

  As we all known, when we call a constructor of a class like this: instance := TSomeClass.Create; The Delphi compiler actually do the following things: Call the static NewInstance method to allocate memory and initialize the memory layout. Call the constructor method to perform the initialization of the class Call the AfterConstruction method It's simple and easy to understand. but I'm not very sure how the compiler handle exceptions in the second and the third step. It seems there are no explicit way to create an instance using a RTTI constructor method in D2010. so I wrote a simple function in the Spring Framework for Delphi to reproduce the process of the creation. class function TActivator.CreateInstance(instanceType: TRttiInstanceType; constructorMethod: TRttiMethod; const arguments: array of TValue): TObject; var classType: TClass; begin TArgument.CheckNotNull(instanceType, 'instanceType'); TArgument.CheckNotNull(constructorMethod, 'constructorMethod'); classType := instanceType.MetaclassType; Result := classType.NewInstance; try constructorMethod.Invoke(Result, arguments); except on Exception do begin if Result is TInterfacedObject then begin Dec(TInterfacedObjectHack(Result).FRefCount); end; Result.Free; raise; end; end; try Result.AfterConstruction; except on Exception do begin Result.Free; raise; end; end; end; I feel it maybe not 100% right. so please show me the way. Thanks!

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• C# Fun with Generics - Mutual Dependencies

  - by Kenneth Cochran

  As an experiment I'm trying to write a generic MVP framework. I started with: public interface IPresenter<TView> where TView: IView<IPresenter<... { TView View { get; set;} } public interface IView<TPresenter> where TPresenter:IPresenter<IView<... { TPresenter Presenter { get; set; } } Obviously this can't work because the types of TView and TPresenter can't be resolved. You'd be writing Type<Type<... forever. So my next attempt looked like this: public interface IView<T> where T:IPresenter { ... } public interface IView:IView<IPresenter> { } public interface IPresenter<TView> where TView: IView { ... } public interface IPresenter: IPresenter<IView> { ... } This actually compiles and you can even inherit from these interfaces like so: public class MyView : IView, IView<MyPresenter> { ... } public class MyPresenter : IPresenter, IPresenter<MyView> { ... } The problem is in the class definition you have to define any members declared in the generic type twice. Not ideal but it still compiles. The problem's start creeping up when you actually try to access the members of a Presenter from a View or vice versa. You get an Ambiguous reference when you try to compile. Is there any way to avoid this double implementation of a member when you inherit from both interfaces? Is it even possible to resolve two mutually dependent generic types at compile time?

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• Android ArrayList<Location> passing between activities

  - by squixy

  I have simple class Track, which stores information about route: import java.io.Serializable; import java.util.ArrayList; import java.util.Date; import android.location.Location; public class Track implements Serializable { private static final long serialVersionUID = -5317697499269650204L; private Date date; private String name; private int time; private double distance, speed; private ArrayList<Location> route; public Track(String name, int time, double distance, ArrayList<Location> route) { this.date = new Date(); this.name = name; this.time = time; this.distance = distance; this.speed = distance / (time / 3600.); this.route = route; } public String getDate() { return String.format("Date: %1$td-%1$tb-%1$tY%nTime: %1$tH:%1$tM:%1$tS", date); } public String getName() { return name; } public int getTime() { return time; } public double getDistance() { return distance; } public float getSpeed() { return (float) speed; } public ArrayList<Location> getRoute() { return route; } @Override public String toString() { return String.format("Name: %s%nDate: %2$td-%2$tb-%2$tY%nTime: %2$tH:%2$tM:%2$tS", name, date); } } And I'm passing it from one activity to another: Intent showTrackIntent = new Intent(TabSavedActivity.this, ShowTrackActivity.class); showTrackIntent.putExtra("track", adapter.getItem(position)); startActivity(showTrackIntent); Where (Track object is element on ListView). I get error during passing Track object: java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = classes.Track) What is happening?

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• problems selecting a mutliple select value from database in Rails

  - by Ramy

  From inside of a form_for in rails, I'm inserting multiple select values into the database, like this: <div class="new-partner-form"> <%= form_for [:admin, matching_profile.partner, matching_profile], :html => {:id => "edit_profile", :multipart => true} do |f| %> <%= f.submit "Submit", :class => "hidden" %> <div class="rounded-block quarter-wide radio-group"> <h4>Exclude customers from source:</h4> <%= f.select :source, User.select(:source).group(:source).order(:source).map {|u| [u.source,u.source]}, {:include_blank => false}, {:multiple => true} %> <%= f.error_message_on :source %> </div> I'm then trying to pull the value from the database like this: def does_not_contain_source(matching_profiles) Expression.select(matching_profiles, :source) do |keyword| Rails.logger.info("Keyword is : " + keyword) @customer_source_tokenizer ||= Tokenizer.new(User.select(:source).where("id = ?", self.owner_id).map {|u| u.source}[0]) #User.select("source").where("id = ?", self.owner_id).to_s) @customer_source_tokenizer.divergent?(keyword) end end but getting this: ExpressionErrors: Bad syntax: --- - "" - B - "" this is what the value is in the database but it seems to choke when i access it this way. What's the right way to do this?

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• Unit testing with Mocks. Test behaviour not implementation

  - by Kenny Eliasson

  Hi.. I always had a problem when unit testing classes that calls other classes, for example I have a class that creates a new user from a phone-number then saves it to the database and sends a SMS to the number provided. Like the code provided below. public class UserRegistrationProcess : IUserRegistration { private readonly IRepository _repository; private readonly ISmsService _smsService; public UserRegistrationProcess(IRepository repository, ISmsService smsService) { _repository = repository; _smsService = smsService; } public void Register(string phone) { var user = new User(phone); _repository.Save(user); _smsService.Send(phone, "Welcome", "Message!"); } } It is a really simple class but how would you go about and test it? At the moment im using Mocks but I dont really like it [Test] public void WhenRegistreringANewUser_TheNewUserIsSavedToTheDatabase() { var repository = new Mock<IRepository>(); var smsService = new Mock<ISmsService>(); var userRegistration = new UserRegistrationProcess(repository.Object, smsService.Object); var phone = "0768524440"; userRegistration.Register(phone); repository.Verify(x => x.Save(It.Is<User>(user => user.Phone == phone)), Times.Once()); } [Test] public void WhenRegistreringANewUser_ItWillSendANewSms() { var repository = new Mock<IRepository>(); var smsService = new Mock<ISmsService>(); var userRegistration = new UserRegistrationProcess(repository.Object, smsService.Object); var phone = "0768524440"; userRegistration.Register(phone); smsService.Verify(x => x.Send(phone, It.IsAny<string>(), It.IsAny<string>()), Times.Once()); } It feels like I am testing the wrong thing here? Any thoughts on how to make this better?

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• How can I use a custom configured RememberMeAuthenticationFilter in spring security?

  - by Sebastian

  I want to use a slightly customized rememberme functionality with spring security (3.1.0). I declare the rememberme tag like this: <security:remember-me key="JNJRMBM" user-service-ref="gymUserDetailService" /> As I have my own rememberme service I need to inject that into the RememberMeAuthenticationFilter which I define like this: <bean id="rememberMeFilter" class="org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter"> <property name="rememberMeServices" ref="gymRememberMeService"/> <property name="authenticationManager" ref="authenticationManager" /> </bean> I have spring security integrated in a standard way in my web.xml: <filter-name>springSecurityFilterChain</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> Everything works fine, except that the RememberMeAuthenticationFilter uses the standard RememberMeService, so I think that my defined RememberMeAuthenticationFilter is not being used. How can I make sure that my definition of the filter is being used? Do I need to create a custom filterchain? And if so, how can I see my current "implicit" filterchain and make sure I use the same one except my RememberMeAuthenticationFilter instead of the default one? Thanks for any advice and/or pointers!

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• How can I get an IObservable<T> in Rx from a "non-standard" event?

  - by Dan Tao

  Here's what I mean. Suppose I'm working with an API that exposes events, but these events do not follow the standard EventHandler or EventHandler<TEventArgs> signature. One event might look like this, for instance: Public Event Update(ByVal sender As BaseSubscription, ByVal e As BaseEvent) Now, typically, if I want to get an IObservable<TEventArgs> from an event, I can just do this: Dim updates = Observable.FromEvent(Of UpdateEventArgs)( _ target:=updateSource, _ eventName:="Update" _ ) But this doesn't work, because the Update event is not an EventHandler<UpdateEventArgs> -- in fact, there is no UpdateEventArgs -- it's basically just its own thing. Obviously, I could define my own class deriving from EventArgs (i.e., UpdateEventArgs), write another class to wrap the object providing the Update event, give the wrapper class its own Update event that is an EventHandler<UpdateEventArgs>, and get an IObservable<UpdateEventArgs> from that. But that's an annoying amount of work. Is there some way to create an IObservable<[something]> from a "non-standard" event like this, or am I out of luck?

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• Importing data from third party datasource (open architecture design )

  - by mare

  How would you design an application (classes, interfaces in class library) in .NET when we have a fixed database design on our side and we need to support imports of data from third party data sources, which will most likely be in XML? For instance, let us say we have a Products table in our DB which has columns Id Title Description TaxLevel Price and on the other side we have for instance Products: ProductId ProdTitle Text BasicPrice Quantity. Currently I do it like this: Have the third party XML convert to classes and XSD's and then deserialize its contents into strong typed objects (what we get as a result of this process is classes like ThirdPartyProduct, ThirdPartyClassification, etc.). Then I have methods like this: InsertProduct(ThirdPartyProduct newproduct) I do not use interfaces at the moment but I would like them to. What I would like is implement something like public class Contoso_ProductSynchronization : ProductSynchronization InsertProduct(ContosoProduct p) where ProductSynchronization will be an interface or abstract class. There will most likely be many implementations of ProductSynchronization. I cannot hardcode the types - classes like ContosoProduct, NorthwindProduct might be created from the third party XML's (so preferably I would continue to use deserialization). Hopefully someone will understand what I'm trying to explain here. Just imagine you are the seller and you have numerous providers and each one uses their own proprietary XML format. I don't mind the development, which will of course be needed everytime new format appears, because it will only require 10-20 methods to be implemented, I just want the architecture to be open and support that.

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• Android problem with opening a second activity and fails to launch

  - by Capsud

  Hi there, Bear with me as i'm just learning about Android. What i'm trying to do is to open an Activity when i click on a button. This is my code in my main activity public class MainPage extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button restaurants = (Button) findViewById(R.id.widget88); restaurants.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { Intent myIntent = new Intent(view.getContext(), AZRestaurants.class); startActivityForResult(myIntent, 0); } }); //Button location = (Button) findViewById(R.id.location); //location.setOnClickListener(new View.OnClickListener() { //public void onClick(View view) { // Intent myIntent = new Intent(view.getContext(), Location.class); // startActivity(myIntent); //} // }); } The program launches no problem when i just implement the first button (restuarant). But when i try to implement the button that i have commented out it fails to launch. and yes i have added the activity to the manifest file. Can anyone help me please? Thanks.

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• How to Open Multiple PopUp windows with JQuery on form submission (popUps should be relative to form

  - by Ole Jak

  I have A HTML form like this: <form> <fieldset class="ui-widget-content ui-corner-all"> <select id="Streams" class="multiselect ui-widget-content ui-corner-all" multiple="multiple" name="Streams[]"> <option value="35"> Example Name (35)</option> <option value="44"> Example Name (44)</option> <option value="5698"> Example Name (5698)</option> <option value="777"> Example Name (777)</option> <option value="12"> Example Name (12)</option> </select> <input type="submit" class="ui-state-default ui-corner-all" name="submitForm" id="submitForm" value="Play Stream from selected URL's!"/> </fieldset> </form> in my JS + HTML page I use JQuery. As you can see I allow user to select multiple Items. I want to open on Submit button click as many popup windows as many Items he selected in a list. Each popUp window should open some url like www.example.com/test.php?id=OPTION_SELECTED . And here I mean by PopUp Window a real browser window. So for each of the selected options I ll get a pop up window whith diferent url. Please Help.

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• Style row banding and selection in tr:table using CSS

  - by Alex Larzelere

  I've got a tr:table that I need to style using CSS. All the normal style functions of a table are working, but row banding and row selection aren't coming up. When I view the rendered source, I'm not seeing a difference in the rows for an id or class to grab on to, and the official documentation doesn't have any attributes for declaring a style class for either. Is this possible and if so what do I need to do to get my CSS to grab onto it? <tr:table id="myTable" value="#{tableValues}" rowBandingInterval="1"> <tr:column> ##Stuff## </tr:column> <tr:column> ##Stuff## </tr:column> <tr:column> ##Stuff## </tr:column> </tr:table> Edit Let me try to clairfy what's happening. First, using the declaration above tells jsf to generate a table, and the attribute rowBandingInterval tells it to give each row alternating colors (If it was set to 2, then it would do 2 rows one color, 2 rows another, 2 rows the original, etc.) Once the page gets rendered into standard html, trinidad (and jsf) apply their own classes and IDs to the html. My normal procedure is to look at the rendered html, find the class that it is appling and add CSS rules for it. However in this case, no additional styles are added (nothing in the rendered html denotes one row to be different from another). So the question is, how do I tell trinidad to either give alternating rows and the user selected row different classes/IDs for me to grab on to with CSS?

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• Asp.net mvc retriev images from db and display on Page

  - by Trey Carroll

  //Inherits="System.Web.Mvc.ViewPage<FilmFestWeb.Models.ListVideosViewModel>" <h2>ListVideos</h2> <% foreach(BusinessObjects.Video vid in Model.VideoList){%> <div class="videoBox"> <%= Html.Encode(vid.Name) %> <img src="<% vid.ThumbnailImage; %>" /> </div> <%} %> //ListVideosViewModel public class ListVideosViewModel { public IList<Video> VideoList { get; set; } } //Video public class Video { public long VideoId { get; set; } public long TeamId { get; set; } public string Name { get; set; } public string Tags { get; set; } public string TeamMembers { get; set; } public string TranscriptFileName { get; set; } public string VideoFileName { get; set; } public int TotalNumRatings { get; set; } public int CumulativeTotalScore { get; set; } public string VideoUri { get; set; } public Image ThumbnailImage { get; set; } } I am getting the "red x" that I usually associate with image file not found. I have verified that my database table shows <binary data> after the stored proc that uploads the image executes. Any insight or advice would be greatly appreciated.

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• keyUp event heard?: Overridden NSView method

  - by Old McStopher

  UPDATED: I'm now overriding the NSView keyUp method from a NSView subclass set to first responder like below, but am still not seeing evidence that it is being called. @implementation svsView - (BOOL)acceptsFirstResponder { return YES; } - (void)keyUp:(NSEvent *)event { //--do key up stuff-- NSLog(@"key up'd!"); } @end --ORIGINAL POST-- I'm new to Cocoa and Obj-C and am trying to do a (void)keyUp: from within the implementation of my controller class (which itself is of type NSController). I'm not sure if this is the right place to put it, though. I have a series of like buttons each set to a unique key equivalent (IB button attribute) and each calls my (IBAction)keyInput method which then passes the identity of each key onto another object. This runs just fine, but I also want to track when each key is released. --ORIGINAL [bad] EXAMPLE-- @implementation svsController //init //IBActions - (IBAction)keyInput:(id)sender { //--do key down stuff-- } - (void)keyUp:(NSEvent *)event { //--do key up stuff-- } @end Upon fail, I also tried the keyUp as an IBAction (instead of void), like the user-defined keyInput is, and hooked it up to the appropriate buttons in Interface Builder, but then keyUp was only called when the keys were down and not when released. (Which I kind of figured would happen.) Pardon my noobery, but should I be putting this method in another class or doing something differently? Wherever it is, though, I need it be able to access objects owned by the controller class. Thanks for any insight you may have.

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• Inereritance of clousure objects and overriding of methods

  - by bobikk

  I need to extend a class, which is encapsulated in a closure. This base class is following: var PageController = (function(){ // private static variable var _current_view; return function(request, new_view) { ... // priveleged public function, which has access to the _current_view this.execute = function() { alert("PageController::execute"); } } })();` Inheritance is realised using the following function: function extend(subClass, superClass){ var F = function(){ }; F.prototype = superClass.prototype; subClass.prototype = new F(); subClass.prototype.constructor = subClass; subClass.superclass = superClass.prototype; StartController.cache = ''; if (superClass.prototype.constructor == Object.prototype.constructor) { superClass.prototype.constructor = superClass; } } I subclass the PageController: var StartController = function(request){ // calling the constructor of the super class StartController.superclass.constructor.call(this, request, 'start-view'); } // extending the objects extend(StartController, PageController); // overriding the PageController::execute StartController.prototype.execute = function() { alert('StartController::execute'); } Inheritance is working. I can call every PageController's method from StartController's instance. However, method overriding doesn't work: var startCont = new StartController(); startCont.execute(); alerts "PageController::execute". How should I override this method?

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• SPRING: How do you programmatically instantiate classes based on information passed from Flex UI

  - by babyangel86

  Imagine the UI passes back an XMl node as such: <properties> <type> Source </type> <name> Blooper </name> <delay> <type> Deterministic </type> <parameters> <param> 4 </param> </parameters> <delay> <batch> <type> Erlang </type> <parameters> <param> 4 </param> <param> 6 </param> </parameters> <batch> And behind the scene what it is asking that you instantiate a class as such: new Source("blooper", new Exp(4), new Erlang(4,6); The problem lies in the fact that you don't know what class you will need to processing, and you will be sent a list of these class definitions with instructions on how they can be linked to each other. I've heard that using a BeanFactoryPostProcessor might be helpful, or a property editor/convertor. However I am at a loss as to how best to use them to solve my problem. Any help you can provide will be much appreciated.

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• Exposing a service to external systems - How should I design the contract?

  - by Larsi

  Hi! I know this question is been asked before here but still I'm not sure what to select. My service will be called from many 3 party system in the enterprise. I'm almost sure the information the service will collect (MyBigClassWithAllInfo) will change during the products lifetime. Is it still a good idea to expose objects? This is basically what my two alternatives: [ServiceContract] public interface ICollectStuffService { [OperationContract] SetDataResponseMsg SetData(SetDataRequestMsg dataRequestMsg); } // Alternative 1: Put all data inside a xml file [DataContract] public class SetDataRequestMsg { [DataMember] public string Body { get; set; } [DataMember] public string OtherPropertiesThatMightBeHandy { get; set; } // ?? } // Alternative 2: Expose the objects [DataContract] public class SetDataRequestMsg { [DataMember] public Header Header { get; set; } [DataMember] public MyBigClassWithAllInfo ExposedObject { get; set; } } public class SetDataResponseMsg { [DataMember] public ServiceError Error { get; set; } } The xml file would look like this: <?xml version="1.0" encoding="utf-8"?> <Message>   <Header>     <InfoAboutTheSender>...</InfoAboutTheSender>   </Header>   <StuffToCollectWithAllTheInfo>   <stuff1>...</stuff1> </StuffToCollectWithAllTheInfo> </Message> Any thought on how this service should be implemented? Thanks Larsi

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• Saving an active record, in what order are the associated objects saved?

  - by Bryan

  In rails, when saving an active_record object, its associated objects will be saved as well. But has_one and has_many association have different order in saving objects. I have three simplified models: class Team < ActiveRecord::Base has_many :players has_one :coach end class Player < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end class Coach < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end I expected that when team.save is called, team should be saved before its associated coach and players. I use the following code to test these models: t = Team.new team.coach = Coach.new team.save! team.save! returns true. But in another test: t = Team.new team.players << Player.new team.save! team.save! gives the following error: > ActiveRecord::RecordInvalid: > Validation failed: Players is invalid I figured out that team.save! saves objects in the following order: 1) players, 2) team, and 3) coach. This is why I got the error: When a player is saved, team doesn't yet have a id, so validates_presence_of :team_id fails in player. Can someone explain to me why objects are saved in this order? This seems not logical to me.

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• How do I integrate GUI elements from different classes at runtime?

  - by thefourthdoctor

  I'm trying to "future-proof" an application that I'm writing by splitting out those elements that are likely to change over time. In my application I need to be able to adapt to changes in the output format (e.g. today I output to a CSV file, in the future I may need to output directly to a SQL Server database, or to a web service, etc.). I'm handling this by defining an abstract class ("OutputProvider") that I will subclass for each individual case. The one aspect of this that has me stumped is how to provide a configuration GUI that is specific to each concrete class. I have a settings dialog with a tab for output configuration. On that tab I intend to provide a drop-down to select the provider and a JPanel beneath it to hold the contents of the provider-specific GUI. How do I get the right GUI in that panel at runtime and have it behave correctly with respect to events? Also, a bonus would be if there was a way to do this such that in order to add support for new providers I could simply provide a new jar or class file to be dropped in a specific folder and the application could pick that up at startup. I'm using NetBeans and Swing.

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• What if a large number of objects are passed to my SwingWorker.process() method?

  - by Trejkaz

  I just found an interesting situation. Suppose you have some SwingWorker (I've made this one vaguely reminiscent of my own): public class AddressTreeBuildingWorker extends SwingWorker<Void, NodePair> { private DefaultTreeModel model; public AddressTreeBuildingWorker(DefaultTreeModel model) { } @Override protected Void doInBackground() { // Omitted; performs variable processing to build a tree of address nodes. } @Override protected void process(List<NodePair> chunks) { for (NodePair pair : chunks) { // Actually the real thing inserts in order. model.insertNodeInto(parent, child, parent.getChildCount()); } } private static class NodePair { private final DefaultMutableTreeNode parent; private final DefaultMutableTreeNode child; private NodePair(DefaultMutableTreeNode parent, DefaultMutableTreeNode child) { this.parent = parent; this.child = child; } } } If the work done in the background is significant then things work well - process() is called with relatively small lists of objects and everything is happy. Problem is, if the work done in the background is suddenly insignificant for whatever reason, process() receives a huge list of objects (I have seen 1,000,000, for instance) and by the time you process each object, you have spent 20 seconds on the Event Dispatch Thread, exactly what SwingWorker was designed to avoid. In case it isn't clear, both of these occur on the same SwingWorker class for me - it depends on the input data, and the type of processing the caller wanted. Is there a proper way to handle this? Obviously I can intentionally delay or yield the background processing thread so that a smaller number might arrive each time, but this doesn't feel like the right solution to me.

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• How to extend this design for a generic converter in java?

  - by Jay

  Here is a small currency converter piece of code: public enum CurrencyType { DOLLAR(1), POUND(1.2), RUPEE(.25); private CurrencyType(double factor) { this.factor = factor; } private double factor; public double getFactor() { return factor; } } public class Currency { public Currency(double value, CurrencyType type) { this.value = value; this.type = type; } private CurrencyType type; private double value; public CurrencyType getCurrencyType() { return type; } public double getCurrencyValue() { return value; } public void setCurrenctyValue(double value){ this.value = value; } } public class CurrencyConversion { public static Currency convert(Currency c1, Currency c2) throws Exception { if (c1 != null && c2 != null) { c2.setCurrenctyValue(c1.getCurrencyValue() * c1.getCurrencyType().getFactor() * c2.getCurrencyType().getFactor()); return c2; } else throw new Exception(); } } I would like to improve this code to make it work for different units of conversion, for example: kgs to pounds, miles to kms, etc etc. Something that looks like this: public class ConversionManager<T extends Convertible> { public T convert(T c1, T c2) { //return null; } } Appreciate your ideas and suggestions.

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