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• Can the Diamond Problem be really solved?

  - by Mecki

  A typical problem in OO programming is the diamond problem. I have parent class A with two sub-classes B and C. A has an abstract method, B and C implement it. Now I have a sub-class D, that inherits of B and C. The diamond problem is now, what implementation shall D use, the one of B or the one of C? People claim Java knows no diamond problem. I can only have multiple inheritance with interfaces and since they have no implementation, I have no diamond problem. Is this really true? I don't think so. See below: [removed vehicle example] Is a diamond problem always the cause of bad class design and something neither programmer nor compiler needs to solve, because it shouldn't exist in the first place? Update: Maybe my example was poorly chosen. See this image Of course you can make Person virtual in C++ and thus you will only have one instance of person in memory, but the real problem persists IMHO. How would you implement getDepartment() for GradTeachingFellow? Consider, he might be student in one department and teach in another one. So you can either return one department or the other one; there is no perfect solution to the problem and the fact that no implementation might be inherited (e.g. Student and Teacher could both be interfaces) doesn't seem to solve the problem to me.

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• Using SoapExtensionAttributes on client side with async web methods

  - by Maxim Polishchuk

  Hey, I have a simple question. I implemented custom soap extension and registered it into client application configuration file. It works fine. (I would like to implement progress bar functionality like http://msdn.microsoft.com/en-us/library/aa480520.aspx) But I don't like some thing - custom soap extension is invoked by every call of my web service. In order to fix this situation (call WS just by required methods) I implemented custom SoapExtensionAttribute like below: [AttributeUsage(AttributeTargets.Method)] public class CustomSoapExtensionAttribute : SoapExtensionAttribute { public override int Priority { get; set; } public CustomSoapExtensionAttribute() : this (1) { } public CustomSoapExtensionAttribute(int priority) { Priority = priority; } public override Type ExtensionType { get { return typeof(CustomSoapExtension); } } } I added this attribute to required methods of web service proxy classes (and removed registration into client configuration file). My soap extension doesn't invoke when required web methods are calling. Can someone help me to solve this problem or select any other solution? Anotherone, I don't know it is important or not - my required methods are async web methods. Best regards, Maxim

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• Namespace Problem

  - by Tarik

  Hello, Normally we all do use using System.Linq; and using System.Data.Linq; for example on the code-behind and expect we can reach the members of these namespaces from Source Code like <%= Something.First()%> but when I wrote it, asp.net said it couldn't find First() in the context and I had to add <%@ Import Namespace="System.Linq" which looked very weird to me but it worked out. Since they are targeting at the same class why they both need separate namespace importing. Code-behind : using System; using System.Data.Linq; using System.Linq; using System.Text namespace Something { class Items : System.Web.UI { //... } } but also I need to add the same Linq namespace on the Html Source part <%@Import Namespace="System.Linq"%> Do I know something wrong or this is some kind of bug in asp.net. I thought when the page is compiling, asp.net combines these two classes and converts html source code into cs class and indicates the control in Control c= new Control(); hierarchy. Thanks in advance.

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• TDD test data loading methods

  - by Dave Hanson

  I am a TDD newb and I would like to figure out how to test the following code. I am trying to write my tests first, but I am having trouble for creating a test that touches my DataAccessor. I can't figure out how to fake it. I've done the extend the shipment class and override the Load() method; to continue testing the object. I feel as though I end up unit testing my Mock objects/stubs and not my real objects. I thought in TDD the unit tests were supposed to hit ALL of the methods on the object; however I can never seem to test that Load() code only the overriden Mock Load My tests were write an object that contains a list of orders based off of shipment number. I have an object that loads itself from the database. public class Shipment { //member variables protected List<string> _listOfOrders = new List<string>(); protected string _id = "" //public properties public List<string> ListOrders { get{ return _listOfOrders; } } public Shipment(string id) { _id = id; Load(); } //PROBLEM METHOD // whenever I write code that needs this Shipment object, this method tries // to hit the DB and fubars my tests // the only way to get around is to have all my tests run on a fake Shipment object. protected void Load() { _listOfOrders = DataAccessor.GetOrders(_id); } } I create my fake shipment class to test the rest of the classes methods .I can't ever test the Real load method without having an actual DB connection public class FakeShipment : Shipment { protected new void Load() { _listOfOrders = new List<string>(); } } Any thoughts? Please advise. Dave

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• Help to understand the issue with protected method

  - by zeroed

  I'm reading Sybex Complete Java 2 Certification Study Guide April 2005 (ISBN0782144195). This book is for java developers who wants to pass java certification. After a chapter about access modifiers (along with other modifiers) I found the following question (#17): True or false: If class Y extends class X, the two classes are in different packages, and class X has a protected method called abby(), then any instance of Y may call the abby() method of any other instance of Y. This question confused me a little. As far as I know you can call protected method on any variable of the same class (or subclasses). You cannot call it on variables, that higher in the hierarchy than you (e.g. interfaces that you implement). For example, you cannot clone any object just because you inherit it. But the questions says nothing about variable type, only about instance type. I was confused a little and answered "true". The answer in the book is False. An object that inherits a protected method from a superclass in a different package may call that method on itself but not on other instances of the same class. There is nothing here about variable type, only about instance type. This is very strange, I do not understand it. Can anybody explain what is going on here?

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• Help me create a Firefox extension (Javascript XPCOM Component)

  - by Johnny Grass

  I've been looking at different tutorials and I know I'm close but I'm getting lost in implementation details because some of them are a little bit dated and a few things have changed since Firefox 3. I have already written the javascript for the firefox extension, now I need to make it into an XPCOM component. This is the functionality that I need: My Javascript file is simple, I have two functions startServer() and stopServer. I need to run startServer() when the browser starts and stopServer() when firefox quits. Edit: I've updated my code with a working solution (thanks to Neil). The following is in MyExtension/components/myextension.js. Components.utils.import("resource://gre/modules/XPCOMUtils.jsm"); const CI = Components.interfaces, CC = Components.classes, CR = Components.results; // class declaration function MyExtension() {} MyExtension.prototype = { classDescription: "My Firefox Extension", classID: Components.ID("{xxxx-xxxx-xxx-xxxxx}"), contractID: "@example.com/MyExtension;1", QueryInterface: XPCOMUtils.generateQI([CI.nsIObserver]), // add to category manager _xpcom_categories: [{ category: "profile-after-change" }], // start socket server startServer: function () { /* socket initialization code */ }, // stop socket server stopServer: function () { /* stop server */ }, observe: function(aSubject, aTopic, aData) { var obs = CC["@mozilla.org/observer-service;1"].getService(CI.nsIObserverService); switch (aTopic) { case "quit-application": this.stopServer(); obs.removeObserver(this, "quit-application"); break; case "profile-after-change": this.startServer(); obs.addObserver(this, "quit-application", false); break; default: throw Components.Exception("Unknown topic: " + aTopic); } } }; var components = [MyExtension]; function NSGetModule(compMgr, fileSpec) { return XPCOMUtils.generateModule(components); }

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• Oracle T4CPreparedStatement memory leaks?

  - by Jay

  A little background on the application that I am gonna talk about in the next few lines: XYZ is a data masking workbench eclipse RCP application: You give it a source table column, and a target table column, it would apply a trasformation (encryption/shuffling/etc) and copy the row data from source table to target table. Now, when I mask n tables at a time, n threads are launched by this app. Here is the issue: I have run into a production issue on first roll out of the above said app. Unfortunately, I don't have any logs to get to the root. However, I tried to run this app in test region and do a stress test. When I collected .hprof files and ran 'em through an analyzer (yourKit), I noticed that objects of oracle.jdbc.driver.T4CPreparedStatement was retaining heap. The analysis also tells me that one of my classes is holding a reference to this preparedstatement object and thereby, n threads have n such objects. T4CPreparedStatement seemed to have character arrays: lastBoundChars and bindChars each of size char[300000]. So, I researched a bit (google!), obtained ojdbc6.jar and tried decompiling T4CPreparedStatement. I see that T4CPreparedStatement extends OraclePreparedStatement, which dynamically manages array size of lastBoundChars and bindChars. So, my questions here are: Have you ever run into an issue like this? Do you know the significance of lastBoundChars / bindChars? I am new to profiling, so do you think I am not doing it correct? (I also ran the hprofs through MAT - and this was the main identified issue - so, I don't really think I could be wrong?) I have found something similar on the web here: http://forums.oracle.com/forums/thread.jspa?messageID=2860681 Appreciate your suggestions / advice.

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• JVM/CLR Source-compatible Language Options

  - by Nathan Voxland

  I have an open source Java database migration tool (http://www.liquibase.org) which I am considering porting to .Net. The majority of the tool (at least from a complexity side) is around logic like "if you are adding a primary key and the database is Oracle use this SQL. If database is MySQL use this SQL. If the primary key is named and the database is Postgres use this SQL". I could fork the Java codebase and covert it (manually and/or automatically), but as updates and bug fixes to the above logic come in I do not want to have to apply it to both versions. What I would like to do is move all that logic into a form that can be compiled and used by both Java and .Net versions naively. The code I am looking to convert does not contain any advanced library usage (JDBC, System.out, etc) that would vary significantly from Java to .Net, so I don't think that will be an issue (at worst it can be designed around). So what I am looking for is: A language in which I can code common parts of my app in and compile it into classes usable by the "standard" languages on the target platform Does not add any runtime requirements to the system Nothing so strange that it scares away potential contributors I know Python and Ruby both have implementations on for the JVM and CLR. How well do they fit my requirements? Has anyone been successful (or unsuccesful) using this technique for cross-platform applications? Are there any gotcha's I need to worry about?

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• Groovlet + Tomcat: "unable to resolve class" when importing libraries

  - by Rob Hruska

  I'm having some trouble running a groovy servlet (groovlet) in tomcat that imports a library class. When I don't import anything the groovlet works correctly, but if I do import something that I expect to be on the classpath (I can import the same class successfully in a regular servlet), I see the following error: groovy.util.ScriptException: Could not parse scriptName: /MyGroovlet.groovy java.lang.RuntimeException: groovy.util.ScriptException: Could not parse scriptName: /MyGroovlet.groovy at groovy.servlet.GroovyServlet$1.call(GroovyServlet.java:123) ... Caused by: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, /MyGroovlet.groovy: 1: unable to resolve class com.mycompany.mypackage.MyLibraryClass @ line 1, column 1. The jar containing MyLibraryClass is in shared/lib, which is loaded by tomcat by the following in catalina.properties: shared.loader=...,${catalina.base}/shared/lib/*.jar,... My groovlets are mapped as described in the user guide in my application's web.xml: <servlet> <servlet-name>GroovyServlet</servlet-name> <servlet-class>groovy.servlet.GroovyServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>GroovyServlet</servlet-name> <url-pattern>*.groovy</url-pattern> </servlet-mapping> And here's the code for the groovlet, MyGroovlet.groovy: import com.mycompany.mypackage.MyLibraryClass MyLibraryClass.someStaticMethod() My groovlet is deployed to WEB-INF/groovy/MyGroovlet.groovy, per the GroovyServlet API. When I visit http://localhost:8080/myapplication/MyGroovlet.groovy, the error described previously is written to my application logs. Is there some way that I need to explicitly declare the runtime classpath for GroovyServlet? I've tried moving the library jar to several places, including WEB-INF/lib and moving the actual MyLibraryClass.class file to WEB-INF/classes, but with no luck.

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• General N-Tier Architecture Question

  - by whatispunk

  In an N-Tier app you're supposed to have a business logic layer and a data access layer. Is it bad to simply have two assemblies: BusinessLogicLayer.dll and DataAccessLayer.dll to handle all this logic? How do you actually represent these layers. It seems silly, the way I've seen it, to have a BusinessLogic class library containing classes like: CustomerBusinessLogic.cs, OrderBusinessLogic.cs, etc. each calling their appropriately named cousin in the DataAccessLayer class library, i.e. CustomerDataAccess.cs, OrderDataAccess.cs. I want to create a web app using MVP and it doesn't seem so cut and dry as this. There are lots of opinions about where the business logic is supposed to be put in MVP and I'm not sure I've found a really great answer yet. I want this project to be easily testable, and I am trying to adhere to TDD methodologies as best I can. I intend to use MSTest and Rhino Mocks for testing. I was thinking of something like the following for my architecture: I'd use LINQ-To-SQL to talk to the database. WCF services to define data contract interfaces for the business logic layer. Then use MVP with ASP.NET Forms for the UI/BLL. Now, this isn't the start of this project, most of the LINQ stuff is already done, so its stuck. The WCF service would replace the existing DataAccessLayer assembly and the UI/BLL would replace the BusinessLogicLayer assembly etc. This sort of makes sense in my head, but its getting really late. Anyone that's traveled down this path have any guidance? Good links? Warnings? Thanks!

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• Kohana 3 jQuery/AJAX request not working

  - by dscher

  I am trying to post some data to a controller in Kohana 3 using the jQuery AJAX method. I seem to have an issue with the data not getting to where I want it to be. I want the data to go to the /application/classes/controller/stock.php file where the file will process the data. I can't seem to figure this one out. Hopefully someone can help. My jQuery ajax call is: $.ajax({ type: 'POST', url: 'add_stock', data: { 'links': 'link_array' } }); 'add_stock' is the name of the action within the controller. I didn't know what else to try. I've also tried '.' and './' hoping that would be right but it's not. In Firebug, although it says the request was 200 OK, I see that the "RESPONSE" is "Failed to load source for: http://localhost/ddm/v2/stocks/add_stock" and my script in my controller which grabs the data isn't working. Here is that code in case it helps: $links = $_POST['links']; $link_obj = Jelly::factory('link') ->set('stock', $stock->id) ->set('links', $links); $link_obj->save(); I think that the problem is that I'm giving the ajax call the ROUTE and not the actual page it needs to deliver the POST data to. I just can't figure it out here. Any help?

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• jackson failing to map empty array with No content to map to Object due to end of input

  - by ijabz

  I send a query to an api and map the json results to my classes using Jackson. When I get some results it works fine, but when there are no results it fails with java.io.EOFException: No content to map to Object due to end of input at org.codehaus.jackson.map.ObjectMapper._initForReading(ObjectMapper.java:2766) at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2709) at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1854) at com.jthink.discogs.query.DiscogsServerQuery.mapQuery(DiscogsServerQuery.java:382) at com.jthink.discogs.query.SearchQuery.mapQuery(SearchQuery.java:37)* But the thing is the api isn't returning nothing at all, so I dont see why it is failing. Here is the query: http://api.discogs.com/database/search?page=1&type=release&release_title=nude+and+rude+the+best+of+iggy+pop this is what I get back { "pagination": { "per_page": 50, "pages": 1, "page": 1, "urls": {}, "items": 0 }, "results": [] } and here is the top level object Im trying to map to public class Search { private Pagination pagination; private Result[] results; public Pagination getPagination() { return pagination; } public void setPagination(Pagination pagination) { this.pagination = pagination; } public Result[] getResults() { return results; } public void setResults(Result[] results) { this.results = results; } } Im guessing the problem is something to do with the results array being returned being blank, but cant see what Im doing wrong EDIT: The comment below was correct, although I usually receive { "pagination": { "per_page": 50, "pages": 1, "page": 1, "urls": {}, "items": 0 }, "results": [] } and in these cases there is no problem but sometimes I seem to just get an empty String. Now Im wondering if the problem is how I read from the inputstream if (responseCode == HttpURLConnection.HTTP_OK) InputStreamReader in= new InputStreamReader(uc.getInputStream()); BufferedReader br= new BufferedReader(in); while(br.ready()) { String next = br.readLine(); sb.append(next); } return sb.toString(); } although I dont read until I get the response code, is it possible that the first time I call br.ready() that I call it before it is ready, and therefore I don't read the input EDIT 2: Changing above code to simply String line; while ((line = br.readLine()) != null) { sb.append(line); } resolved the issue.

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• Is there an easy way to get the Scala REPL to reload a class or package?

  - by Rex Kerr

  I almost always have a Scala REPL session or two open, which makes it very easy to give Java or Scala classes a quick test. But if I change a class and recompile it, the REPL continues with the old one loaded. Is there a way to get it to reload the class, rather than having to restart the REPL? Just to give a concrete example, suppose we have the file Test.scala: object Test { def hello = "Hello World" } We compile it and start the REPL: ~/pkg/scala-2.8.0.Beta1-prerelease$ bin/scala Welcome to Scala version 2.8.0.Beta1-prerelease (Java HotSpot(TM) Server VM, Java 1.6.0_16). Type in expressions to have them evaluated. Type :help for more information. scala> Test.hello res0: java.lang.String = Hello World Then we change the source file to object Test { def hello = "Hello World" def goodbye = "Goodbye, Cruel World" } but we can't use it: scala> Test.goodbye <console>:5: error: value goodbye is not a member of object Test Test.goodbye ^ scala> import Test; <console>:1: error: '.' expected but ';' found. import Test;

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• Lazarus - why I can't assign event to run-time component?

  - by Garret Raziel

  Hello, I have this Lazarus program: unit Unit2; {$mode objfpc}{$H+} interface uses Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs, StdCtrls, ComCtrls; type { TForm2 } TForm2 = class(TForm) procedure OnTlacitkoClick(Sender: TObject); procedure FormClose(Sender: TObject; var CloseAction: TCloseAction); procedure FormCreate(Sender: TObject); tlac:TButton; private { private declarations } public { public declarations } end; var Form2: TForm2; implementation { TForm2 } procedure TForm2.OnTlacitkoClick(Sender: TObject); begin showmessage('helloworld'); end; procedure TForm2.FormCreate(Sender: TObject); var i,j:integer; begin tlac:=TButton.Create(Form2); tlac.OnClick:=OnTlacitkoClick; tlac.Parent:=Form2; tlac.Left:=100; tlac.Top:=100; end; initialization {$I unit2.lrs} end. but compiler says: unit2.pas(63,32) Error: Wrong number of parameters specified for call to "OnTlacitkoClick" in tlac.OnClick:=OnTlacitkoClick; expression. I have searched and think that this is legal expression in Delphi. I want simply to registrate OnTlacitkoClick as tlac.OnClick event,not to call this procedure. Is there somethink wrong with the code or must I do it different in Lazarus/Freepascal? Thanks.

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• Maintain one to one mapping between objects

  - by Rohan West

  Hi there, i have the following two classes that provide a one to one mapping between each other. How do i handle null values, when i run the second test i get a stackoverflow exception. How can i stop this recursive cycle? Thanks [TestMethod] public void SetY() { var x = new X(); var y = new Y(); x.Y = y; Assert.AreSame(x.Y, y); Assert.AreSame(y.X, x); } [TestMethod] public void SetYToNull() { var x = new X(); var y = new Y(); x.Y = y; y.X = null; Assert.IsNull(x.Y); Assert.IsNull(y.X); } public class X { private Y _y; public Y Y { get { return _y; } set { if(_y != value) { if(_y != null) { _y.X = null; } _y = value; if(_y != null) { _y.X = this; } } } } } public class Y { private X _x; public X X { get { return _x; } set { if (_x != value) { if (_x != null) { _x.Y = null; } _x = value; if (_x != null) { _x.Y = this; } } } } }

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• How to propagate .java file change to .class under eclipse, tomcat & stripes

  - by BigBourin

  Hi, i'm new to java and i got some problems. i'm developping a web application using the framework stripes on tomcat 6.0. I'm working with eclipse EE on windows. i successfully managed to get the stripes example application (called Bugzooky) up and running on my tomcat server. I imported the .war file and stripes libs in Eclipse. Here is the stripes archive containing the examples and libs But now i'm trying to change the example source files to learn how does it work. but whatever the modification made to the source files "WebContent/WEB-INF/src/*.java", nothing change! even after restarting the server. i noticed that the classes are compiled into .class files in the "ImportedClasses" folder, and tomcat always use these files, they are never updated, and if i removed one of them, the application just don't start. it look like my source files don't exists! I also tried to build my webapp from scratch, but when i tried to use the features used in the example files (like SecurityFilter.java): import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import ... It ends up with plenty of: the import javax.servlet.Filter cannot be resolved I checked the Librairies and it look like i'm using exactly the same as the example. It's probably something i didn't understood about java but i googled 100 times yesterday, and i can't find the solution (i probably didn't search the right place because i don't really understand my problem). I hope you'll be able to help me.

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• Custom model validation of dependent properties using Data Annotations

  - by Darin Dimitrov

  Since now I've used the excellent FluentValidation library to validate my model classes. In web applications I use it in conjunction with the jquery.validate plugin to perform client side validation as well. One drawback is that much of the validation logic is repeated on the client side and is no longer centralized at a single place. For this reason I'm looking for an alternative. There are many examples out there showing the usage of data annotations to perform model validation. It looks very promising. One thing I couldn't find out is how to validate a property that depends on another property value. Let's take for example the following model: public class Event { [Required] public DateTime? StartDate { get; set; } [Required] public DateTime? EndDate { get; set; } } I would like to ensure that EndDate is greater than StartDate. I could write a custom validation attribute extending ValidationAttribute in order to perform custom validation logic. Unfortunately I couldn't find a way to obtain the model instance: public class CustomValidationAttribute : ValidationAttribute { public override bool IsValid(object value) { // value represents the property value on which this attribute is applied // but how to obtain the object instance to which this property belongs? return true; } } I found that the CustomValidationAttribute seems to do the job because it has this ValidationContext property that contains the object instance being validated. Unfortunately this attribute has been added only in .NET 4.0. So my question is: can I achieve the same functionality in .NET 3.5 SP1? UPDATE: It seems that FluentValidation already supports clientside validation and metadata in ASP.NET MVC 2. Still it would be good to know though if data annotations could be used to validate dependent properties.

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• How to serialize a protected property in wcf

  - by Denis Rosca

  Hello, i need some help with wcf serializing. I have two classes Person and Address. The Address class looks like this: public class Adresa : IExtensibleDataObject { private Guid _id; [DataMember] protected virtual Guid Id { get { return _id; } set { _id = value; } } private ExtensionDataObject _extensionData; [DataMember] public virtual ExtensionDataObject ExtensionData { get { return _extensionData; } set { _extensionData = value; } } private string _street; [DataMember] public virtual string Street { get { return this._cUTAM; } set { this._cUTAM = value; } } private string _number; [DataMember] public virtual string Number { get { return this._number; } set { this._number = value; } } private string _postalCode; [DataMember] public virtual string PostalCode { get { return this._postalCode; } set { this._postalCode = value; } } // and some other stuff related to the address } The Person class looks like this: public class PersoanaFizica :IExtensibleDataObject { private Guid _id; [DataMember] protected virtual Guid Id { get { return _id; } set { _id = value; } } private ExtensionDataObject _extensionData; [DataMember] public virtual ExtensionDataObject ExtensionData { get { return _extensionData; } set { _extensionData = value; } } private string _firstName; [DataMember] public virtual string FirstName { get { return this._firstName; } set { this._firstName = value; } } private string _lastName; [DataMember] public virtual string LastName { get { return this._lastName; } set { this._lastName = value; } } } The problem is that when the wcf client the data the Id properties are set to a bunch of zeros ( something like 000000-0000-000000-0000000). Any ideas on why this is happening? Thanks, Denis.

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• AutoMapper and flattening nested arrays

  - by Bryan Slatner

  I'm trying to use AutoMapper to flatten multiple levels of arrays. Consider the following source classes: class X { public string A { get; set; } public Y[] B { get; set; } } class Y { public string C { get; set; } public Z[] D { get; set; } } class Z { public string E { get; set; } public string F { get; set; } } And the following destination: class Destination { public string A { get; set; } public string C { get; set; } public string E { get; set; } public string F { get; set; } } What I'd like to be able to do is get a List from one or more X, e.g.: Mapper.Map<IEnumerable<X>, IEnumerable<Destination>>(arrayOfX); I'm unable to figure out what sort of mapping configuration to use to achieve this. MapFrom seems like the way to go for 1:1 compositions, but doesn't seem to be able to handle the array (or other enumerable) unless I use AutoMapper's destination naming convention. Any insights on how to achieve this?

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• Using prepared statements with JDBCTemplate

  - by Bernhard V

  Hi. I'm using the Jdbc template and want to read from the database using prepared statements. I iterate over many lines in a csv file and on every line I execute some sql select queries with it's values. Now I want to speed up my reading from the database but I just can't get the Jdbc template to work with prepared statements. Actually I even don't know how to do it. There is the PreparedStatementCreator and the PreparedStatementCreator. As in this example both of them are created with anonymous inner classes. But inside the PreparedStatementCreator class I don't have access to the values I want to set in the prepared statement. Since I'm iterating through a csv file I can't hard code them as a String because I don't know them. I also can't pass them to the PreparedStatementCreator because there are no arguments for the constructor. I was used to the creation of prepared statements being fairly simple. Something like PreparedStatement updateSales = con.prepareStatement( "UPDATE COFFEES SET SALES = ? WHERE COF_NAME LIKE ? "); updateSales.setInt(1, 75); updateSales.setString(2, "Colombian"); updateSales.executeUpdate(): as in the Java tutorial. Your help would be very appreciated.

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• AS3: Array of objects parsed from XML remains with zero length

  - by Joel Alejandro

  I'm trying to parse an XML file and create an object array from its data. The data is converted to MediaAlbum classes (class of my own). The XML is parsed correctly and the object is loaded, but when I instantiate it, the Albums array is of zero length, even when the data is loaded correctly. I don't really know what the problem could be... any hints? import Nem.Media.*; var mg:MediaGallery = new MediaGallery("test.xml"); trace(mg.Albums.length); MediaGallery class: package Nem.Media { import flash.net.URLRequest; import flash.net.URLLoader; import flash.events.*; public class MediaGallery { private var jsonGalleryData:Object; public var Albums:Array = new Array(); public function MediaGallery(xmlSource:String) { var loader:URLLoader = new URLLoader(); loader.load(new URLRequest(xmlSource)); loader.addEventListener(Event.COMPLETE, loadGalleries); } public function loadGalleries(e:Event):void { var xmlData:XML = new XML(e.target.data); var album; for each (album in xmlData.albums) { Albums.push(new MediaAlbum(album.attribute("name"), album.photos)); } } } } XML test source: <gallery <albums <album name="Fútbol 9" <photos <photo width="600" height="400" filename="foto1.jpg" / <photo width="600" height="400" filename="foto2.jpg" / <photo width="600" height="400" filename="foto3.jpg" / </photos </album <album name="Fútbol 8" <photos <photo width="600" height="400" filename="foto4.jpg" / <photo width="600" height="400" filename="foto5.jpg" / <photo width="600" height="400" filename="foto6.jpg" / </photos </album </albums </gallery

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• Python Locking Implementation (with threading module)

  - by Matty

  This is probably a rudimentary question, but I'm new to threaded programming in Python and am not entirely sure what the correct practice is. Should I be creating a single lock object (either globally or being passed around) and using that everywhere that I need to do locking? Or, should I be creating multiple lock instances in each of the classes where I will be employing them. Take these 2 rudimentary code samples, which direction is best to go? The main difference being that a single lock instance is used in both class A and B in the second, while multiple instances are used in the first. Sample 1 class A(): def __init__(self, theList): self.theList = theList self.lock = threading.Lock() def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList): self.theList = theList self.lock = threading.Lock() self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": aList = [] for x in range(10): B(aList) A(aList).poll() Sample 2 class A(): def __init__(self, theList,lock): self.theList = theList self.lock = lock def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList,lock): self.theList = theList self.lock = lock self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": lock = threading.Lock() aList = [] for x in range(10): B(aList,lock) A(aList,lock).poll()

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• How to use bll, dal and model?

  - by bruno

  Dear all, In my company I must use a Bll, Dal and model layer for creating applications with a database. I've learned at school that every databasetable should be an object in my model. so I create the whole model of my database. Also I've learned that for every table (or model object) there should be a DAO created into the DAL. So I do this to. Now i'm stuck with the BLL classes. I can write a BLLclass for each DAO/ModelObject or I can write a BLLclass that combine some (logic) DAO's... Or i can write just one Bllclass that will manage everything. (this last one I'm sure it aint the best way..) What is the best practice to handle this Bll 'problem'? And a second question. If a bll is in need of tablecontent from an other table where it aint responsible for, whats the best way to get the content? Go ask on the responsible BLL or go directly to the DAO? I'm struggling with these questions the last 2 months, and i don't know what is the best way to handle it.

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• What's a good way of building up a String where you specific start and end locations?

  - by Michael Campbell

  (java 1.5) I have a need to build up a String, in pieces. I'm given a set of (sub)strings, each with a start and end point of where they belong in the final string. Was wondering if there were some canonical way of doing this. This isn't homework, and I can use any licensable OSS, such as jakarta commons-lang StringUtils etc. My company has a solution using a CharBuffer, and I'm content to leave it as is (and add some unit tests, of which there are none (?!)) but the code is fairly hideous and I would like something easier to read. As I said this isn't homework, and I don't need a complete solution, just some pointers to libraries or java classes that might give me some insight. The String.Format didn't seem QUITE right... I would have to honor inputs too long and too short, etc. Substrings would be overlaid in the order they appear (in case of overlap). As an example of input, I might have something like: String:start:end FO:0:3 (string shorter than field) BAR:4:5 (String larger than field) BLEH:5:9 (String overlays previous field) I'd want to end up with FO BBLEH 01234567890

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• use of assertions for type checking in php?

  - by user151841

  I do some checking of arguments in my classes in php using exception-throwing functions. I have functions that do a basic check ( ===, in_array etc ) and throw an exception on false. So I can do assertNumeric($argument, "\$argument is not numeric."); instead of if ( ! is_numeric($argument) ) { throw new Exception("\$argument is not numeric."); } Saves some typing I was reading in the comments of the php manual page on assert() that As noted on Wikipedia - "assertions are primarily a development tool, they are often disabled when a program is released to the public." and "Assertions should be used to document logically impossible situations and discover programming errors— if the 'impossible' occurs, then something fundamental is clearly wrong. This is distinct from error handling: most error conditions are possible, although some may be extremely unlikely to occur in practice. Using assertions as a general-purpose error handling mechanism is usually unwise: assertions do not allow for graceful recovery from errors, and an assertion failure will often halt the program's execution abruptly. Assertions also do not display a user-friendly error message." This means that the advice given by "gk at proliberty dot com" to force assertions to be enabled, even when they have been disabled manually, goes against best practices of only using them as a development tool So, am I 'doing it wrong'? What other/better ways of doing this are there?

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