Can't serialize class error when using references

[Johan Haleby]

Hi, 

I've just started to use References in Morphia but immediately I run into an error. I have an entity that references another entity:

public class Entity1 {

    @Reference(value = "entity2", lazy = true)

     private Entity2 entity2;

     ...

}

Entity2 looks like this:

public class Entity2 {

    @Id

     private Entity2Id Id;

     ...

}

Entity2Id looks like this:

public class Entity2Id {

    private String x;

    private String y;     

} 

The error message I get when persisting an instance of Entity1 is:

java.lang.IllegalArgumentException: can't serialize class com.mycompany.Entity2Id

at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:234)

at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:140)

at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:224)

at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:140)

at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:86)

at com.mongodb.DefaultDBEncoder.writeObject(DefaultDBEncoder.java:27)

at com.mongodb.OutMessage.putObject(OutMessage.java:142)

at com.mongodb.DBApiLayer$MyCollection.update(DBApiLayer.java:346)

at com.mongodb.DBCollection.update(DBCollection.java:165)

at com.mongodb.DBCollection.save(DBCollection.java:736)

at com.google.code.morphia.DatastoreImpl.save(DatastoreImpl.java:767)

at com.google.code.morphia.DatastoreImpl.save(DatastoreImpl.java:830)

at com.google.code.morphia.DatastoreImpl.save(DatastoreImpl.java:824)

at com.google.code.morphia.dao.BasicDAO.save(BasicDAO.java:109)

I'm using the snapshot version of Morphia. Can't you use Morphia with references that has compund ids like this or am I doing something wrong?

Regards,

/Johan

[Johan Haleby]

I think this is a bug i Morphia. In the Mapper class there's a method called keyToRef that returns:

new DBRef(null, key.getKind(), key.getId());

When the Id of the key is not a type that Mongo recognizes it will fail with the exception I described in the previous message. If I change it to:

return new DBRef(null, key.getKind(), toDBObject(key.getId()));

for non-Mongo objects it works.

Regards,

/Johan

[Johan Haleby]

There seems to be a related problem because if you apply my code change then a ClassCastException is thrown when the ReferenceMapper#readSingle(..) method is called because of this line:

DBRef dbRef = (DBRef) mf.getDbObjectValue(dbObject);

The object I get back is not a DBRef but a BasicDBObject.

/Johan

[Maaz]

what you should be doing is 

public class Entity2Id implements Serializable

That's what i am seeing from exception

Thanks

[Johan Haleby]

Thanks for your tip, perhaps it could be that simple. Right now I've reverted my code since my work-around was too complex. I'll see if your suggestion works next time I try out references.

Regards,

/Johan