Estrutura de agregação do Mongodb para grails 1.3.7

    compile "org.mongodb:mongo-java-driver:2.10.1"
    runtime "com.gmongo:gmongo:1.1"
}

    compile (":mongodb:1.1.0.GA"){
        excludes 'mongo-java-driver', 'gmongo'
    }
}

    DBObject match = new BasicDBObject('$match', new BasicDBObject("adPostId", 50) );

    // build the $projection operation
    DBObject fields = new BasicDBObject("adPostId", 1);
    fields.put("shopperId", 1);
    fields.put("_id", 0);
    DBObject project = new BasicDBObject('$project', fields );

    // Now the $group operation
    DBObject groupFields = new BasicDBObject( "_id", '$karmaType');
    groupFields.put("average", new BasicDBObject( '$sum', '$rating'));
    DBObject group = new BasicDBObject('$group', groupFields);

    // run aggregation
    AggregationOutput output = db.karma.aggregate( match, project, group );