Question

I would like to be able to use the mongodb group command with the ‘keyf’ parameter through the java driver. Has anyone been successful with this?

Answer 1

You have to use the deprecated method DBCollection.group(DBObject args) and add the key function javascript code as a string under the DBObject key named “$keyf”.

BasicDBObject args  = new BasicDBObject();
args.put("ns", nameSpace);
args.put( "initial" , initialDBObject );
args.put( "cond" , queryDBObject );
args.put( "$reduce" , reduceJavasriptCodeString );
args.put("$keyf", keyfJavascriptCodeString );
if( finalize != null ) args.put("finalize", finalizeJavascriptCodeString );
DBObject groupResult = mydbCollection.group(args);