ConcurrentModificationException with self-referring entity-class when not
running the enhancer
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Key: OPENJPA-641
URL: https://issues.apache.org/jira/browse/OPENJPA-641
Project: OpenJPA
Issue Type: Bug
Components: build / infrastructure, datacache, jpa
Affects Versions: 1.1.0, 1.0.2
Environment: Happens when not running the enhancer. Note that the
problem also occurs when the Multithreaded property is set.
Reporter: Pål GD
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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