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JPA 2.0 metamodel and composite ids

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Masterhard

Post subject: JPA 2.0 metamodel and composite ids

Posted: Wed Aug 11, 2010 4:47 pm

Newbie

Joined: Wed Aug 11, 2010 4:31 pm
Posts: 1

I have a class:

Code:

@Entity
@IdClass(BadPojo.PK.class)
public class BadPojo implements Serializable {
    @Id
    int id1;

    @Id
    int id2;

    String value;

    public class PK implements Serializable {
        int id1;
        int id2;

        @Override
        public boolean equals(Object o) {...}

        @Override
        public int hashCode() {...}
    }
}

For this class I can obtain only 'value' attribute with EntityType.getDeclaredSingularAttribute.
I can get id1 attribute only iterating through EntityType.getIdClassAttributes() and comparing attribute names. The other option to get the attribute is using static schema mapping.

If I remove @IdClass annotation and BadPojo.PK class, I can not get id1 and id2 attributes for using in criteria query at all. Attributes are unavailable and static schema mapping field is not assigned.

If I leave only one @Id annotation, I can obtain all three attributes with EntityType.getDeclaredSingularAttribute.

Iterating through EntityType.getIdClassAttributes() does not seem to be good practice. If such hibernate behavior correct or it is a bug?

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Anne Buit

Post subject: Re: JPA 2.0 metamodel and composite ids

Posted: Wed Jul 13, 2011 9:15 am

Newbie

Joined: Wed May 04, 2011 2:24 am
Posts: 10

I am running into the same problem, applying Predicates, Orders and other manipulations on composite ID's is very cumbersome because of this.

A simple piece of code, like this:

Code:

Root<ProjectActivity> root = query.from(ProjectActivity.class);
query.multiselect(root.get("projectId"), root.get("projectActivityId"), root.get("name"));

turns into a big chunck of code:

Code:

Root<ProjectActivity> root = query.from(ProjectActivity.class);
EntityType<ProjectActivity> et = e.getMetamodel().entity(ProjectActivity.class);
Path<?>[] attributes = new Path<?>[3];
for(SingularAttribute<? super ProjectActivity, ?> s : et.getIdClassAttributes()){
   if(s.getName().equals("projectId"))
      attributes[0] = root.get(s);
   if(s.getName().equals("projectActivityId"))
      attributes[1] = root.get(s);
}
attributes[2] = root.get("name");
query.multiselect(attributes);

Any ideas on how to deal with this?

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