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POEntityManager injection -> NullPointerException
 

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    <p>My project is running on Glassfish 3.0.1 I'm trying to use @PersistenceContext annotation to inject EntityManager. Here is my code:</p> <pre><code>@Stateless public class UserBean implements UserBeanRemote { @PersistenceContext(unitName = "RHDManagementPlatformPU") private EntityManager em; public UserBean() { if (this.em == null) { System.err.println("NULL"); } } ... } </code></pre> <p>In console I get error message "NULL". I already saw 5-6 topics which are similar to mine. But the only thing I understood is maybe the problem is in my persistence.xml. Here is it:</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="RHDManagementPlatformPU" transaction-type="JTA"&gt; &lt;provider&gt;oracle.toplink.essentials.PersistenceProvider&lt;/provider&gt; &lt;jta-data-source&gt;dev_magi_entities&lt;/jta-data-source&gt; &lt;exclude-unlisted-classes&gt;false&lt;/exclude-unlisted-classes&gt; &lt;properties&gt; &lt;property name="toplink.ddl-generation" value="create-tables"/&gt; &lt;/properties&gt; &lt;/persistence-unit&gt; &lt;/persistence&gt; </code></pre> <p>I'tried to find on the internet how to configure this file, but did not find where the issue could be. Maybe someone have any idea or tutorial, manual links which can help me to better understand how this beast works =)</p>
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