Hello.

I'm (still) trying to use the entity listeners to keep an history of the changes made to a certain type of entity.

The code for my test entity is as follows:

--------------------------------------Car-----------------------------------------

package ejb3.tests.entitylistener.persistence;

import ...

@Entity
@Table(name = "CAR")
public class Car {

private static long initialId = 0;

@EmbeddedId
private CarId id;

@Column(name = "HP")
private int horsePower;

//I would generate the in key in @PrePersist, but hibernate
//checks the key before calling it
public Car() {
this.id = new CarId();
}

public CarId getId() {
return this.id;
}

public void setId(CarId id) {
this.id = id;
}

public int getHorsePower() {
return this.horsePower;
}

public void setHorsePower(int horsePower) {
this.horsePower = horsePower;
}

@PrePersist
public void createNewId() {
System.out.println("PrePersist Me: " + this);
if(this.id.getId() == 0) {
synchronized(Car.class) {
this.id.setId(++initialId);
this.id.setVersion(1);
}
}
}

@PostPersist
public void createHistoricRecord() throws NamingException {
System.out.println("PostPersist Me: " + this);
if(this.id.getVersion() == 1) {
synchronized(Car.class) {
InitialContext ic = new InitialContext();
Object o = ic.lookup( "java:/EntityListenerTestOtherEntityManager");
EntityManager em = (EntityManager)o;
Car copy = new Car();
long carIdId = this.id.getId();
int carIdVersion = this.id.getVersion();
copy.id = new CarId(carIdId, carIdVersion - 1);
System.out.println("PostPersist The Copy: " + copy);
em.persist(copy);
em.flush();
}
}
}
}

----------------------------------------CarId-------------------------------------

package ejb3.tests.entitylistener.persistence;

import ...
@Embeddable
public class CarId implements java.io.Serializable {

private static final long serialVersionUID = 1;

private long id;
private int version;

public CarId() {
}

public CarId(long id, int version) {
this.id = id;
this.version = version;
}


@Column(name="ID", nullable=false)
public long getId() {
return this.id;
}

public void setId(long id) {
this.id = id;
}

@Column(name="VERSION", nullable=false)
public int getVersion() {
return this.version;
}

public void setVersion(int version) {
this.version = version;
}


public boolean equals(Object other) {
if ( (this == other ) ) return true;
if ( (other == null ) ) return false;
if ( !(other instanceof CarId) ) return false;
CarId castOther = ( CarId ) other;
return (this.getId()==castOther.getId())
&& (this.getVersion()==castOther.getVersion());
}

public int hashCode() {
int result = 17;
result = 37 * result + (int) this.getId();
result = 37 * result + this.getVersion();
return result;
}
}

----------------------------------------------------------------------------------

If I create a new instance of Car am call EntityManager.persist on that instance, I get an exception, like:

Exception in thread "main" javax.ejb.EJBException: javax.persistence.PersistenceException: org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [ejb3.tests.entitylistener.persistence.Car#ejb3.tests.entitylistener.persistence.CarId@5b0e] ...

The output on the JBoss window is the following:

15:49:50,430 INFO [STDOUT] PrePersist Me: ejb3.tests.entitylistener.persistence.Car@c98b07

15:49:50,852 INFO [STDOUT] PostPersist Me: ejb3.tests.entitylistener.persistence.Car@c98b07

15:49:50,852 INFO [STDOUT] PostPersist The Copy: ejb3.tests.entitylistener.persistence.Car@f2ff9b

15:49:50,852 INFO [STDOUT] PrePersist Me: ejb3.tests.entitylistener.persistence.Car@f2ff9b

15:49:50,852 INFO [STDOUT] PostPersist Me: ejb3.tests.entitylistener.persistence.Car@c98b07

15:49:50,852 INFO [STDOUT] PostPersist The Copy: ejb3.tests.entitylistener.persistence.Car@16b5518

15:49:50,852 INFO [STDOUT] PrePersist Me: ejb3.tests.entitylistener.persistence.Car@16b5518

Please clarify me something: shouldntt the second @PostPersist be applied to the Car copy? I thing it should, but as you can see it's being applyed again to the original Car. Is it a bug or is this the correct behaviour? If it's a bug, is there anyway to circumvent it?

I will now try to create a history records using a native SQL query.

Thanks in advance for any input.

Hugo Oliveira

hugom.oliveira.ext@siemens.com