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POPersistency unit fails to make the relation many to many
 

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    <p>Ok this is a weird problem because I had it working before. So I have 2 classes: game and developer. They have a many to many relationship. The persistency unit makes automatically the table game_developer. Thus there are 3 tables: game developer and game_developer. When I enter Information inside the database. The table game and developer will get there values as normal but the table game_developer will remain empty. So the relationship isn't recognized. Also when I run the webapp everything inside the tables should be dropped. The developer drops fine but the game remains to exist.</p> <p>Any push in the right direction is appreciated.</p> <p>Thank you in advance,</p> <p>David</p> <p>Initialization:</p> <pre><code>try { gameOrganizer = (GameOrganizer) getServletContext().getAttribute("database"); Game game = new Game("Counter Strike: source"); Game game2 = new Game("Battlefield: bad company 3"); Game game3 = new Game("Killing floor"); Developer devel = new Developer("valve"); Developer devel2 = new Developer("EA Games"); Developer devel2b = new Developer("DICE"); Developer devel3 = new Developer("Ubisoft"); //The GameOrganizer is the controller between the model en the view. //The view being the website. //So gameOrganizer.addGame(game) will persist the object to the database. gameOrganizer.addGame(game); gameOrganizer.addGame(game2); gameOrganizer.addGame(game3); gameOrganizer.addDeveloper(devel); gameOrganizer.addDeveloper(devel2); gameOrganizer.addDeveloper(devel2b); gameOrganizer.addDeveloper(devel3); game.addDeveloper(devel); devel.getGames().add(game); game2.addDeveloper(devel2); devel2.getGames().add(game2); game2.addDeveloper(devel2b); devel2b.getGames().add(game2); game3.addDeveloper(devel3); devel3.getGames().add(game3); } catch (DatabaseException ex) { Logger.getLogger(GameController.class.getName()).log(Level.SEVERE, null, ex); } catch (DomainException ex) { Logger.getLogger(GameController.class.getName()).log(Level.SEVERE, null, ex); } </code></pre> <p>The game class:</p> <pre><code>@Entity public class Game implements Serializable{ private String gameNaam; private double prijs; @ManyToMany(mappedBy = "games") private Collection&lt;Developer&gt; developers = new ArrayList&lt;Developer&gt;(); @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; public Game(){}; . . //methods . . } </code></pre> <p>The Developer class</p> <pre><code>@Entity public class Developer implements Serializable { private String naam; private String info; @ManyToMany private Collection&lt;Game&gt; games = new ArrayList&lt;Game&gt;(); @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; public Developer() { } . . //methods . . } </code></pre> <p>The persistency Unit:</p> <pre><code> &lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"&gt; &lt;persistence-unit name="GameDatabaseSitePU" transaction-type="RESOURCE_LOCAL"&gt; &lt;provider&gt;oracle.toplink.essentials.PersistenceProvider&lt;/provider&gt; &lt;class&gt;domainmodel.Developer&lt;/class&gt; &lt;class&gt;domainmodel.Game&lt;/class&gt; &lt;exclude-unlisted-classes&gt;false&lt;/exclude-unlisted-classes&gt; &lt;properties&gt; &lt;property name="toplink.jdbc.user" value="app"/&gt; &lt;property name="toplink.jdbc.password" value="app"/&gt; &lt;property name="toplink.jdbc.url" value="jdbc:derby://localhost:1527/GameDatabase;create=true"/&gt; &lt;property name="toplink.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/&gt; &lt;property name="toplink.ddl-generation" value="drop-and-create-tables"/&gt; &lt;/properties&gt; &lt;/persistence-unit&gt; &lt;/persistence&gt; </code></pre>
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