mongodb upsert from java: how to get _id of existing object?

Question

I'm using the mongo-jackson-wrapper with java and MongoDB. I find an object by querying a field of mine (not the _id field), and then I need to know the _id field value, whether the net result was an update or an insert. However, I get an exception:

com.mongodb.MongoException: No objects to return
    at net.vz.mongodb.jackson.WriteResult.getSavedId(WriteResult.java:97)

The exception comes from the wrapper, not the MongoDB driver itself.

WriteResult<EntityDocument, String> wr 
   = coll.update(DBQuery.is("corefEntityId", corefEntityId), up, true,  false);

What (if anything) is the right way to do this?

Answer 1

You need to use findAndModify and set returnNew to true

You can view the JavaDoc

This code should do the trick but I haven't tested it.

coll.findAndModify(DBQuery.is("corefEntityId", corefEntityId), null, null, false, up, true, false);