Query By Example

[gutzeit]

Hi,

Is there a way to execute query by example using Morphia?

Something like:

User exampleUser = new User("em...@ddd.com");

User realUser = ds.createQuery(User.class).filter("this", exampleEntity).get();

[Scott Hernandez]

No, but I can add it to the list. You can do this with embedded
objects, just not the root entity.

I'm thinking something like:

ds.QBE(exampleUser).get/asList()

Is QBE a good method name, or maybe "queryByExample"?

[gutzeit]

queryByExample sounds pretty straight forward :-)

BTW, I can do it now like this:

User example = new User();

example.setEmail("em...@gmail.com");

DBObject dbObject = morphia.toDBObject(example);

BasicDBObject userEntryDbObj = (BasicDBObject) ds.getDB().getCollection("users").findOne(dbObject);

User userEntry = morphia.fromDBObject(User.class, userEntryDbObj);

But its does not look "morpheesh" :-)

[Scott Hernandez]

Yeah, I didn't give that example, but that is one of the current
work-arounds. I added the feature. It will be 1.0.

[gutzeit]

Scott, when is 1.0 planned to be released ?

BTW, If anyone is interested in a workaround meanwhile, a generic method of doing so:

public D getByExample(D example, Class objectClass) {

    DBObject dbObject = morphia.toDBObject(example);

    // Find out the entity name by reflection.

    Entity annotation = (Entity) objectClass.getAnnotation(Entity.class);

    String collectionName = annotation.value();

    BasicDBObject entryDbObj = (BasicDBObject) ds.getDB().getCollection(collectionName).findOne(dbObject);

    D entry = (D) morphia.fromDBObject(objectClass, entryDbObj);

    return entry;

}

[Scott Hernandez]

On Sun, Feb 6, 2011 at 3:23 PM, gutzeit <gut...@gmail.com> wrote:
> Scott, when is 1.0 planned to be released ?

When the code is done :)

I will put up a snapshot today.

This is not the best code because it assumes that you specify the
collection name in the @Entity annotation; It is also very low-level.

You can use the Query(Impl) class to do most of this stuff which makes
it much cleaner.
http://code.google.com/p/morphia/source/browse/trunk/morphia/src/main/java/com/google/code/morphia/DatastoreImpl.java

[gutzeit]

Yeap, thanks. My knowledge of Query is very limited, I will try to do better.

Waiting for snapshots ;-)

[Scott Hernandez]

The snapshot is up.