JPA query many to one association

Question

I want to build the following pseudo query

Select a From APDU a where a.group.id= :id

group is a field in APDU class of the type APDUGroup.class.

I just want to get a list of APDUs based on APDUGroup's id.

How do i do that using a standard JPA query?

UPDATE

Yes, I have tried the above query and tried other variations for hours before posting in S/O. Here is the generated SQL for the query above:

SELECT t1.ID, t1.status, t1.type, t1.modified, t1.response, t1.expectedSize, t1.created, t1.description, t1.sequence, t1.name, t1.command, t1.recurring, t1.auth, t1.createdBy, t1.APDUGroup, t1.modifiedBy FROM APDUGroup t0, APDU t1 WHERE ((t0.ID = ?) AND (t0.ID = t1.APDUGroup))

The query looks okay but nothing get selected from my table. There are at least 100 APDUs with APDUGroup = 1 in my test database.

I'm using eclipselink as the JPA provider.

Answer 1

Given the following Entities:

@Entity
public class APDU implements Serializable {
    @Id
    @GeneratedValue
    private Long id;

    @ManyToOne
    private APDUGroup group;

    //...

}

@Entity
public class APDUGroup implements Serializable {
    @Id
    @GeneratedValue
    private Long id;

    //...
}

The following query will return a list of APDUs for a given APDUGroup id:

select a from APDU a where a.group.id = :id

Oh, wait, that's your query :)