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POJPA exception: Object: ... is not a known entity type
 

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    <p>I'm new to JPA and I'm having problems with the autogeneration of primary key values.</p> <p>I have the following entity:</p> <pre><code>package jpatest.entities; import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; @Entity public class MyEntity implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; public Long getId() { return id; } public void setId(Long id) { this.id = id; } private String someProperty; public String getSomeProperty() { return someProperty; } public void setSomeProperty(String someProperty) { this.someProperty = someProperty; } public MyEntity() { } public MyEntity(String someProperty) { this.someProperty = someProperty; } @Override public String toString() { return "jpatest.entities.MyEntity[id=" + id + "]"; } } </code></pre> <p>and the following main method in other class:</p> <pre><code>public static void main(String[] args) { EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPATestPU"); EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); MyEntity e = new MyEntity("some value"); em.persist(e); /* (exception thrown here) */ em.getTransaction().commit(); em.close(); emf.close(); } </code></pre> <p>This is my persistence 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="JPATestPU" transaction-type="RESOURCE_LOCAL"&gt; &lt;provider&gt;oracle.toplink.essentials.PersistenceProvider&lt;/provider&gt; &lt;class&gt;jpatest.entities.MyEntity&lt;/class&gt; &lt;properties&gt; &lt;property name="toplink.jdbc.user" value="..."/&gt; &lt;property name="toplink.jdbc.password" value="..."/&gt; &lt;property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/jpatest"/&gt; &lt;property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/&gt; &lt;property name="toplink.ddl-generation" value="create-tables"/&gt; &lt;/properties&gt; &lt;/persistence-unit&gt; &lt;/persistence&gt; </code></pre> <p>When I execute the program I get the following exception in the line marked with the proper comment:</p> <pre><code>Exception in thread "main" java.lang.IllegalArgumentException: Object: jpatest.entities.MyEntity[id=null] is not a known entity type. at oracle.toplink.essentials.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:3212) at oracle.toplink.essentials.internal.ejb.cmp3.base.EntityManagerImpl.persist(EntityManagerImpl.java:205) at jpatest.Main.main(Main.java:...) </code></pre> <p><strong>What am I missing?</strong></p>
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