How to use Morphia's update(...) method with a QueryDSL query?

[Andreas Oberhoff]

Hello,

in Morphia, using update(...) methods goes like this:

Morphia morphia = new Morphia();
Datastore datastore = morphia.createDatastore("MorphiaSampleDb");
Hotel hotel = new Hotel("Fairmont", 3, new Address("1 Rideau Street", "Ottawa", "K1N8S7", "Canada"));
datastore.save(hotel);

Query<Hotel> updateQuery = datastore.createQuery(Hotel.class).field("_id").equal(hotel.getId());
UpdateOperations<Hotel> datastore.createUpdateOperations(Hotel.class).set("name", "Fairmont Chateau Laurier");
datastore.update(updateQuery, ops);

Problem here is the updateQuery object which is not a type safe QueryDSL query.

Is there an option converting a QueryDSL query to a Morphia query or any other trick of solving this problem? Maybe its a missing feature...

Best regards,

Andreas

[timowest]

Hi Andreas.

This is currently not supported. But contributions are welcome.

Timo

[Andreas]

I wrote a quick and dirty workaround for this:

QHotel qHotel = QHotel.hotel;
MorphiaQuery<Hotel> query = new MorphiaQuery<Hotel>(morphia, datastore, qHotel);
query.where(qHotel.id.eq(hotel.getId());
 
Query<Hotel> q = createMorphiaQuery(Hotel.class, query, datastore);
UpdateOperations<Hotel> ops = datastore.createUpdateOperations(Hotel.class).set(field(qHotel.name), "New Name");

datastore.update(q, ops);

The helper methods:

private <T> Query<T> createMorphiaQuery(Class<T> kind, MorphiaQuery<T> query, Datastore datastore)
     throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException,
     InvocationTargetException {
 Query<T> q = datastore.createQuery(kind);
 DBObject o = (DBObject) JSON.parse(query.toString());
 Method m = q.getClass().getMethod("setQueryObject", DBObject.class);
 m.invoke(q, o);
 return q;
}

private String field(StringPath path) {
 String field = path.toString();
 return field.substring(field.indexOf(".") + 1);
}

Now updating with Morphia and QueryDSL in a type safe manner is no problem anymore.

Best regards,
Andreas

[timowest]

Hi Andreas.

Thanks for the code samples.

Timo

[Gaspard Petit]

Hello,

I initially implemented my solution based on Andreas answer.  Although the createMorphiaQuery hack scares me, it works fine.  The Update however was slightly more tricky - it worked in most simple cases but failed on others.  For example, if your object contains a map and you do q.someMap.get("aKey").something, you will end up with a field value of "someMap.get(aKey).something" instead of "someMap.aKey.something".

You can easily get a stronger QueryDSL Path -> Mongo Path using the MorphiaSerializer that is part of QueryDSL.  It works like this:

MorphiaSerializer serializer = new MorphiaSerializer(morphia);

String field = serializer.visit(path, null);

Gaspard

[Gaspard Petit]

Update to the thread - Timo has updated the AbstractMongoDbQuery in QueryDSL so we can now extract the DBObject (see https://github.com/querydsl/querydsl/pull/1851/commits/a9d96c7ee17bb1df8e3ee6bfda699b3fba92d806).

In the code posted by Andreas, instead of 

Query<T> q = datastore.createQuery(kind);
DBObject o = (DBObject) JSON.parse(query.toString());

One can now write

Query<T> q = datastore.createQuery(kind);

DBObject o = query.asDBObject();

Thus saving unnecessary serialization-deserialization.