Details
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Bug
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Status: Closed
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Major
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Resolution: Cannot Reproduce
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1.0.2, 1.1.0
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None
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Happens when not running the enhancer. Note that the problem also occurs when the Multithreaded property is set.
Description
Sometimes while fetching an instance of an entity-class with a self-reference (ManyToOne, for creating a hierarchy), I get a ConcurrentModificationException. This only seems to happen when the enhancer hasn't been loaded. Also it seems there has to be multiple levels in the hierarchy for this to occur.
I have created an example which reproduces the Exception.
The code:
@Entity
public class A {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
@ManyToOne
@Column(name = "parent")
private A parent;
public A()
{ name = ""; }public A(String name)
{ this.name = name; }public static void main(String[] args)
{ EntityManagerFactory emf = Persistence .createEntityManagerFactory("system"); EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); // a A a = new A("a"); em.persist(a); // b A b = new A("b"); b.setParent(a); em.persist(b); // c A c = new A("c"); c.setParent(b); em.persist(c); em.getTransaction().commit(); em.close(); // getting c's data int cId = c.getId(); String cName = c.getName(); em = emf.createEntityManager(); em.getTransaction().begin(); //both methods of getting entity results in same error // A newC = em.find(A.class, cId); Query q = em.createQuery("SELECT a FROM A a WHERE a.name=:cName") .setParameter(1, cName); A newC = (A)q.getSingleResult(); em.getTransaction().commit(); em.close(); System.out.println(newC); emf.close(); }//getters and setters
}
persistence.xml:
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
version="1.0">
<persistence-unit name="system" transaction-type="RESOURCE_LOCAL">
<class>no.tecwel.A</class>
<properties>
<!-- this has no effect
<property name="openjpa.Multithreaded" value="true"/> -->
<property name="openjpa.ConnectionURL" value="jdbc:mysql://db.home.local/system "/>
<property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver"/>
<property name="openjpa.ConnectionUserName" value="username"/>
<property name="openjpa.ConnectionPassword" value="password"/>
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(SchemaAction='add,deleteTableContents',ForeignKeys='true')"/>
<property name="openjpa.Log" value="DefaultLevel=TRACE"/>
</properties>
</persistence-unit>
</persistence>
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- Closed
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