EJB 3 Entity persist and merge bug?

[jlowcock]

I have a simple entity that uses a generated primary key. If I simply persist the entity every thing works in terms of the database however the generated primary key value is not set in the class instance I have persisted. If I persist and then merge the result the generated value is then set in my class instance however there are two row created in the database one for the first scenario and then one for the second scenario. This implies to me that the persist operation is creating an internally cached version of the class which is then merged/copied when I call the merge operation.

Is there an operation I need to call after persist, or an additional annotation, or what, in order to have the generated value appear in the class instance without having to call merge.

Is the behaviour of the persist/merge combination a bug in that it creates two rows in the database?

Here is the code for my entity.

@Entity (name = "P002Ledger")
@Table (name = "P002_LEDGER")
public class Ledger
implements Serializable
{
static final
private long serialVersionUID = -147023002293214496L;

static final
private Reporter _reporter = Reporter.getReporter(Ledger.class);

private long m_code;

private String m_name;

public Ledger ()
{

}

public Ledger (long code)
{
m_code = code;
}

public Ledger (String name)
{
m_name = name;
}

@Id
@SequenceGenerator(name="p002_ledger_code_seq", allocationSize=25)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="p002_ledger_code_seq")
@Column (name="ledger_code",nullable=false)
public long getCode()
{
return m_code;
}

protected void setCode(long code)
{
m_code = code;
}

@PostPersist
protected void askCode()
{
_reporter.trace("code = "+getCode());
}

@Column (name="ledger_name",nullable=false)
public String getName()
{
return m_name;
}

public void setName(String name)
{
m_name = name;
}
}



This is the code I have used to generate the persist/merge scenario. The service methodsare simple wrappers around em.persist and em.merge.

Ledger ledger = new Ledger("Gen Barry");
service.insertLedger(ledger);
assertTrue(ledger.getCode() == 0);
ledger = service.updateLedger(ledger);
assertTrue(ledger.getCode() != 0);

[juergen.zimmermann]

1) The database generates the new id (sequence number)
2) The generated id is propagated to the JBoss appserver and therefore inside the server-side object
3) Do you send the server-side object with the generated id back to the ejb3 client? If not, on the client-side you'll the the original object having the initial value instead of a generated id.

[jlowcock]

Thank you for the reply this is obviously one of my duh moments. I of course had forgotten the pass-by-value semantics and have not passed the server side object back to the client.