In the MongoDB java driver, how do I pass a key function ('keyf') to a 'group' command

I would like to be 开发者_开发百科able to use the mongodb group command with the 'keyf' parameter through the java driver. Has anyone been successful with this?

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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);

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This piece of code should do the work for you:

public static CommandResult exeMapReduceAlikeGroupCmd(DB db, String colName, String keyFunc, DBObject query,
                                                      String reduceFunc, DBObject initial) {
    BasicDBObject cmd = new BasicDBObject("ns", colName);// this is the collection name
    cmd.append("$keyf", keyFunc);// keyf function
    cmd.append("cond", query); // cond query object
    cmd.append("$reduce", reduceFunc);// reduce function
    cmd.append("initial", initial);// initial value
    cmd = new BasicDBObject("group", cmd);
    return db.command(cmd, db.getOptions());
}