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• How do I persist a Java property of type Object using Hibernate?

  - by afielden

  I have a Java class with a property like this private Object myObj; When I try to save the class using Hibernate annotations, I get the rather confusing error message "property mapping has wrong number of columns". What is the correct approach to persisting a class containing a generic property such as this?

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• Conditional on WebClient

  - by CarryFlag

  Given: thin client (JS) model services client use services. services use model. Model consists of (for sample): Rect Circle ... Ellipse services: class CanvasProviger { public Canvas getCanvas() { return new Canvas(); } } model: class Canvas ... { private List < Figure > figures = new List < Figure >; ... } class Circle extends Figure { private int x, y, r; } class Rect extends Figure { private x, y, w, h; } client: ... var figure = MyJSRPCImpl.getCanvas().nextFigure(); if(figure == JSLocalModel.Rect) { drawRect(figure); } else if(figure == JSLocalModel.Circle) { drawCircle(figure); } ... How else can do way conditional? In rich client I used pattern Visitor. // my bad english, I know =(

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• Why do we need a private constructor?

  - by isthatacode

  if a class has a private constructor then it cant be instantiated. so, if i dont want my class to be instantiated and still use it, then i can make it static. what is the use of a private constructor ? Also its used in singleton class, except that, is there any othe use ? (Note : The reason i am excuding the singleton case above is because I dont understand why do we need a singleton at all ? when there is a static class availble. You may not answer for my this confusion in the question. )

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• Is base method able to use derived base data members?

  - by iTayb

  Lets assume we have the following code: abstract class Base1 { protected int num; } class Der1:Base1 { protected Color color; protected string name; } class Der2:Base1 { protected DateTime dthen; } and so on. An array of base1 type exists and includes many objects created out of classes that are derived from base1. Is it possible to define the toString() method in the base class only? something like: public override string toString() { if (this is Der1) return "num = " + this.num + "color = " + this.color.toString() + " name = " this.name; if (this is Der2) return "num = " + this.num + "dthen = " + this.dthen.toString(); // and so on ... } Thank you very much :) P.S. This is not an homework question. I've just wondered about.

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• How can I use the HTML5 <button> tag in Drupal 6

  - by Frankie Yale

  I have the following HTML which I'd like to use in my Drupal 6 theme. It needs to replace the search-box code. <fieldset class="search"> <input type="text" class="box font-myriad" /> <button class="btn" title="Submit Search">Search</button> </fieldset> I'm trying stuff like $vars['form']['button']['#attributes'] = array('class' => 'btn'); in template.php, but no luck so far. Couldn't find much help on drupal.org.

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• Finding object count where a field is unique in Django

  - by Johnd

  I have a model that is something like this: class Input(models.Model): details = models.CharField(max_length=1000) user = models.ForeignKey(User) class Case(Input): title = models.CharField(max_length=200) views = models.IntegerField() class Argument(Input): case = models.ForeignKey(Case) side = models.BooleanField() A user can submit many arguments, per case. I want to be able to say how many users have submitted side=true arguments. I mean if 1 user had 10 arguments and another user had 2 arguments (both side=true) I'd want the count to be 2, not 12.

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• Trying to change img src if another element is visible with jQuery

  - by R.J.

  I have a div ("panel" class) on my page that toggles open/closed on the click of a paragraph element ("flip" class), which has an image inside of it. Here's the HTML: <div class="panel">Contact info</div> <p class="flip"><img src="images/contactExpand.png" />Expand</p> And the jQuery: $(".flip").click(function(){ $(".panel").slideToggle("slow"); }); Everything works fine so far, but I want the image src to change to "contactCollapse.png" when the panel div is visible. This doesn't seem to do anything (image just stays the same): if ($(".panel").is(":visible") == true) { $(".flip img").attr("src","../images/contactCollapse.png") } else { $(".flip img").attr("src","../images/contactExpand.png") } Am I missing something? Thanks for any help!

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• Inferring type from method generics

  - by ng

  I am from a Java background and I am looking from the equivalent in c# for the following. public interface Reader { <T> T read(Class<? extends T> type); } Such that I can do the following, constraining the parameter and inferring the return type. Cat cat = reader.read(Cat.class); Dog dog = reader.read(Dog.class); I was hoping something like this would work in c# but I am not sure it will. public interface Reader { T Read<T>(); } And and do this. public class TypeReader : Reader { public T Read<T>() { Type type = T.GetType(); ... } } Is something like this even possible in c#?

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• Hibernate reverse engineering

  - by EugeneP

  I have a structure where the main table is USER, other tables include CATEGORY (contains user_id). What I got after the standard reverse engineering procedure was: the class User contained a collection of categories, the class Category didn't contain the foreign key (user_id) but it did contain the User object. Why did it not contain the foreign key as a class property? And how do I join these two tables in HQL without that glue? HQL - please explain this part.

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• Problems with capturing an event in child object in Actionscript

  - by Raigomaru

  I have two classes. The first one (the starting class): package { import flash.display.Sprite; import flash.events.KeyboardEvent; import tetris.*; public class TetrisGame extends Sprite { private var _gameWell:Well; public function TetrisGame() { _gameWell = new Well(); addChild(_gameWell); } } } The second: package tetris { import flash.display.Sprite; import flash.events.KeyboardEvent; public class Well extends Sprite { public function Well() { super(); addEventListener(KeyboardEvent.KEY_DOWN, onKeyboard); } private function onKeyboard():void { //some code is here } } } But when I press any buttons on my keyboard, the child class Well doesn't have any reaction. What's the problem?

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• Quick question regarding MVC framework for a java game

  - by Jason

  I have a question regarding the use of the MVC framework for a blackjack game im writing in java. As I understand, my model would be a class that stores the state of the game, and more specifically, each players hand. Within the model class, I would have an array of listeners, which would be notified each time the game state changes (ie a player has drawn a new card). These listeners would be my viewer, which is the class that handles the display of the game. This class would implement the ActionListener interface, and each time the model changes, it would call/"notify" my viewer's actionPerformed method. My question is as follows: I intend to have two JPanels, each devoted to displaying the respective player's hand. As a player draws a new card, a new ImageIcon would be added to the panel. My question is how would the viewer class know what card has been added to the player's hand? I suppose I could store the player's hand before a notify event, and then upon the notification event, compare the new state with the old, to find out what has changed. I'm a complete novice here, so I could be completely wrong, but it seems a bit tedious to do this. Is there a more efficient/common way of detecting what has changed in the model between the before and after state? Another solution would be to redraw the entire panel each time the notification occurs? Would this be a better idea?

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• Null reference but it's not?

  - by Clint Davis

  This is related to my previous question but it is a different problem. I have two classes: Server and Database. Public Class Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Private _databases As List(Of Database) Public Property Databases() As List(Of Database) Get Return _databases End Get Set(ByVal value As List(Of Database)) _databases = value End Set End Property Public Sub LoadTables() Dim db As New Database(Me) db.Name = "test" Databases.Add(db) End Sub End Class Public Class Database Private _server As Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Public Property Server() As Server Get Return _server End Get Set(ByVal value As Server) _server = value End Set End Property Public Sub New(ByVal ser As Server) Server = ser End Sub End Class Fairly simple. I use like this: Dim s As New Server s.Name = "Test" s.LoadTables() The problem is in the LoadTables in the Server class. When it hits Databases.Add(db) it gives me a NullReference error (Object reference not set). I don't understand how it is getting that, all the objects are set. Any ideas? Thanks.

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• Error : The Type Initializer of Daemon.Global threw an exception in c#

  - by srk

  I am using the below class file, where some variables are declared to use in the entire application. Now I used that variable BlockLogOut in another class file to make the value true. I just put this below line and getting error in it.. TypeInitializationException Global.BlockLogOut = True; The weird thing is, it was working fine for many months and i am getting this error now on the above line. Of course i was modifying some other stuffs in the application, but surely not this class file. What would have been the problem? namespace Daemon { class Global { public static bool BlockLogOut = false; } }

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• How do I write a Guice Provider that doesn't explicitly create objects?

  - by ripper234

  Say I have a ClassWithManyDependencies. I want to write a Guice Provider for this class, in order to create a fresh instance of the class several times in my program (another class will depend on this Provider and use it at several points to create new instances). One way to achieve this is by having the Provider depend on all the dependencies of ClassWithManyDependencies. This is quite ugly. Is there a better way to achieve this? Note - I certainly don't want the Provider to depend on the injector. Another option I considered is having ClassWithManyDependencies and ClassWithManyDependenciesProvider extend the same base class, but it's butt ugly.

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• Is inheritance bad nowadays?

  - by mafutrct

  Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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• Integration testing - can it be done right?

  - by Max

  I used TDD as a development style on some projects in the past two years, but I always get stuck on the same point: how can I test the integration of the various parts of my program? What I am currently doing is writing a testcase per class (this is my rule of thumb: a "unit" is a class, and each class has one or more testcases). I try to resolve dependencies by using mocks and stubs and this works really well as each class can be tested independently. After some coding, all important classes are tested. I then "wire" them together using an IoC container. And here I am stuck: How to test if the wiring was successfull and the objects interact the way I want? An example: Think of a web application. There is a controller class which takes an array of ids, uses a repository to fetch the records based on these ids and then iterates over the records and writes them as a string to an outfile. To make it simple, there would be three classes: Controller, Repository, OutfileWriter. Each of them is tested in isolation. What I would do in order to test the "real" application: making the http request (either manually or automated) with some ids from the database and then look in the filesystem if the file was written. Of course this process could be automated, but still: doesn´t that duplicate the test-logic? Is this what is called an "integration test"? In a book i recently read about Unit Testing it seemed to me that integration testing was more of an anti-pattern?

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• How to check if TypeIdenitifier(T) is an Object?

  - by John

  I'm creating a generic list class that has a member of type Array(Array of ). The problem is the class descruction,because the class is supposed to be used for types from byte to types inheriting TObject. Specifically: destructor Destroy; var elem:T; begin /*if(T is Tobject) then //Check if T inherits TObject {Compiler error!} for elem in FData do TObject(elem).Free;*/ // do not know how to do it SetLength(FItems,0); //FItems : Array of T inherited Destroy; end; How do I check if T is TObject so I can free every member if the typeidenitifier is a class,for example?

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• setter injection guice + wicket

  - by chris-gr

  Hi, I have a Wicket Web Page where I create a new Object of class A: A a = new A(User u); In A I would like to have setter injection, however this is actually not done. I have heard that one must provide an empty constructor but how is it possible to have also a non - empty constructor with setter injection?

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• Calling a getter multiple times or calling once and assigning to a variable?

  - by GK

  say suppose I have class as : public class Age { private int age; public int getAge() { return this.age; } } In my Main class I am calling the getAge() method many times. So I wanted to know is it advisable to call so many times or call once and assign it to some variable and use that variable. Which is best and why?

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• Determining where a function is defined in C#?

  - by templatetypedef

  Hey all - I am a complete novice at C# (I've never used it before) and recently needed to look over some code written in it. I spent the longest time trying to track down a nonexistent method in a class that didn't seem to be defined anywhere in the class that was using it. I later found out it was an "extension method," which I gather is a method grafted onto another class by some source. I completely understand the rationale behind this language feature and actually think it's quite nice. However, as someone without much experience in the language, it makes it harder to look up unfamiliar methods, since the method in question could be defined anywhere. My question is this: given an unfamiliar method call in C#, what's the best way for me to look up more info on it, given that it could be an extension method defined in an entirely separate class? Thanks!

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• Tracking changed (unsaved) objects

  - by Eric

  I have a class which is serialized to and from an XML file when the user decided to open or save. I'm trying to add the typical functionality where when they try to close the form with un-saved changes the form warns them and gives them the option of saving before closing. I've added a HasUnsavedChanges property to my class, which my form checks before closing. However, it's a little annoying that my properties have changed from something like this .. public string Name { get; set; } to this... private string _Name; public string Name { get { return _Name; } set { this._Name = value; this.HasUnsavedChanges = true; } } Is there a better way to track changes to an instance of a class? For example is there some standard way I can "hash" an instance of a class into a value that I can use to compare the most recent version with the saved version without mucking up every property in the class?

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• A strange error in java generic.

  - by ???

  This is ok: Class<? extends String> stringClass = "a".getClass(); But this gets error: <T> void f(T obj) { Class<? extends T> objClass = obj.getClass(); } I know I can cast it like: <T> void f(T obj) { @SuppressWarnings("unchecked") Class<? extends T> objClass = (Class<? extends T>) obj.getClass(); } But why the previous error? Will the next release of Java 7 will support such usage?

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• PHP: constant as variable in function

  - by m4recek

  I'm trying to use constant as a function paramter, is it possible to check type of this constant. Example of what I want: class ApiError { const INVALID_REQUEST = 200; } class Response { public function status(ApiError $status) { //function code here } } USE: $response = new Response(); $response->status(ApiError::INVALID_REQUEST); This shoud check that given $status is constant of class ApiError. Is something like this possible?

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• Avoiding sub-type selection in view code

  - by John Donoghue

  Hi, I have some code where the model contains some classes like (vb.net pseudocode, but could be any OO language): Enum AttributeType Boolean Date String End Enum MustInherit Class Attibute Must Override Function Type As AttributeType End Class Class BooleanAttribute: Attribute Function Type As AttributeType Return AttributeType.Boolean End Function End Class And the view contains some code like: Select Case AttributeType Case Boolean //Display checkbox control Case Date //Display date picker control Case String //Display textbox control End Select I don't really like the code in the view, for the hopefully obvious reasons (what happens when I get a new attribute type etc). My question is, how should I replace it? I could easily add a method to the concrete classes, but that pollutes the model with UI stuff so that's a horrible idea. I could move the select into a factory, but that seems to be just hiding the problem. Can anybody advise a better approach?

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• Problem using a costum server control in a aspx

  - by gre3ns0ul

  Hi guys, i am having a issue. I already developed one class (my custom gridview) and i want use it on a .aspx That class is defined in app_code and compiled to the dll of the project. namespace MyCostumControls{  public class DropDownPagingGridView : GridView{ ... I already registered the control on the aspx page using <%@ Register Namespace="MyCostumControls" TagPrefix="ctrl" % and i can use in the page and works ok.. But i'm watching one problem. That class contains methods defined by me, than when i try to call them in code-behind sayd to me than they're not defined. In designed i don't see the reference to MyCostumControls, and when i try declare one field using protected global::MyCostumControls.MyCostumControls ddl_gv_errors, i cannot access to MyCostumControls namespace, Is because he's compiled to the project dll? I can access to all namespaces than are not contained in app_code. Solutions? Apreciate. Thanks

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