Problem finding objets with composite key

[noemi conde]

Hi ranchies !!!
I've got a problem dealing with composite primary keys in hibernate


Here is the code:

@Table(name = "TABLE_A", schema="SCHEM_A")
public class Ejercicio implements java.io.Serializable {


private TableAId id;





@SuppressWarnings("serial")
@Embeddable
public class TableAId implements java.io.Serializable {

@Column(name = "ID_TABLE_A", nullable=false)
private Integer idTableA;

@JoinColumn(name = "ID_COLUM_B")
@ManyToOne
private ColumnB idColumB;

@JoinColumn(table="SCHEMA_B.TABLE_B", name = "ID_TABLE_B")
@ManyToOne
private TABLE_B idTableB;

We have a composite primary key with objects from two different schemas, and we don't know how to do the mapping.

The exception thrown when we try to execute this hql query: "Select A from Table_A" is

com.ibm.db2.jcc.a.SqlException: DB2 SQL error: SQLCODE: -206, SQLSTATE: 42703, SQLERRMC: TABLE_A0_.IDTABLE_A

Do you know what is the problem ???

Any idea is welcome, thanks in advance.

[Karsten Wutzke]

Your mapping is completely wrong. Every entity class that has a composite primary key must have its own ID class, so if you have 2 tables, this will result in 4 classes, 2 entity classes and 2 ID classes.

There are 4 variants of how to declare these:

JPA 1.0 @IdClass
JPA 1.0 @EmbeddedId
JPA 2.0 @IdClass
JPA 2.0 @EmbeddedId

whichever you choose does matter, because JPA implementations (Hibernate, EclipseLink, ...) have a different degree of bugginess with these.

I made a lot of tests and to me the JPA 1.0 @IdClass has the fewest problems. The Hibernate mapping system is very instable and throws many unexpected exceptions, so you might want to try EclipseLink or another JPA provider.

Don't expect ORMs to do what you think. Be prepared.

As for your code, please pick up a good source on how to map composite key classes. I don't have time to correct completely incorrect code.

Karsten

[Karsten Wutzke]

See http://stackoverflow.com/questions/96729/what-are-the-best-books-for-hibernate-jpa

Forget "Java Persistence with Hibernate"! "Pro JPA 2" by Mike Keith is a thousand times better. The former is very bad with composite keys.

Also see http://en.wikibooks.org/wiki/Java_Persistence

Karsten