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ManyToMany mapping created when no mapping is specified [message #1032651]

Wed, 03 April 2013 05:00

Eclipse User

Hi,
In my Entity, when I don't specify the mapping for a collection attribute, by default ManyToMapping is created. Won't an exception be thrown in this case that the mapping is missing? Or is the default behavior to create ManyToMany mapping for collection attribute?

Eg:

public class Parent{
private List<Child> childList;

public List<Child> getChildList(){
return childList;
}

public void setChildList(List<Child> childList){
this.childList = childList;
}
}

The rational for not specifying the mapping is that, I would like to create OneToManyMapping programmatically in the session customizer pointing mappedBy to an entity whose reverse mapping is not known at static weaving time.

Re: ManyToMany mapping created when no mapping is specified [message #1034430 is a reply to message #1032651]

Fri, 05 April 2013 08:22

Eclipse User

One more thing: Parent is a MappedSuperclass.

Re: ManyToMany mapping created when no mapping is specified [message #1034693 is a reply to message #1034430]

Fri, 05 April 2013 15:35

Eclipse User

The JPA specification requires field/properties to use default mappings when one isn't specified. You can either mark the field/property with @Transient, or just replace the default mapping with the OneToManyMapping in the customizer.

Re: ManyToMany mapping created when no mapping is specified [message #1037892 is a reply to message #1034693]

Wed, 10 April 2013 02:13

Eclipse User

Hi Chris,
What do you mean by replace the default mapping with OneToManyMapping in the session customizer, remove the mapping and add?

classDescriptor.getMappings().remove(classDescriptor.getMappingForAttributeName("childList"));
classDescriptor.addMapping(newOneToManyMapping);

Also, I tried marking the attribute with @Transient and creating OneToManyMapping (as given below).

@Transient
private List<Child> childList;

And in the customizer,
OneToManyMapping oneToManyMapping = new OneToManyMapping();
oneToManyMapping.setAttributeName("childList");
oneToManyMapping.useTransparentList();
oneToManyMapping.privateOwnedRelationship();
oneToManyMapping.setCascadeAll(TRUE);
oneToManyMapping.setReferenceClass(Parent.class);
oneToManyMapping.addTargetForeignKeyFieldName("PARENT_ID", "ID");
classDescriptor.addMapping(oneToManyMapping);

When I persist the parent along with childList, the childList is not persisted. Also when I query the parent and then invoke getChildList(), no sql stmt is fired. Looks like the mapping is incorrect. Could you please explain what is missing here? (Note that it works when I don't mark the attribute @Transient and replace the ManyToManyMapping with OneToManyMapping).

[Updated on: Wed, 10 April 2013 14:01] by Moderator

Re: ManyToMany mapping created when no mapping is specified [message #1042450 is a reply to message #1037892]

Tue, 16 April 2013 09:04

Eclipse User

I would recommend using the add/remove, did you try this?

Making it @Transient can affect weaving, as the object is weaved before customizers are run, so the attribute will not get weaved. You could disable "eclipselink.weaving.internal", or disable weaving entirely. Not marking it @Transient, but adding/removing in the customizer is the better solution.

Re: ManyToMany mapping created when no mapping is specified [message #1042459 is a reply to message #1042450]

Tue, 16 April 2013 09:14

Eclipse User

Hi James,
Removing @Transient and remove existing mapping and add new mapping in the customizer works. Just wondering why it didn't work when the attribute is marked with @Transient (also tried by disabling eclipselink.weaving.internal). Just before the parent entity is persisted, if I get the server session and see the mapping for the child attribute, it is present (and with valid reference class). Is there a way to debug what/where the problem is?

Thanks,
Saravanan.

[Updated on: Tue, 16 April 2013 09:45] by Moderator

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