New GroupCommand class for better usability and consistency with M/R

Author: agirbal

src/main/com/mongodb/DBCollection.java

@@ -844,33 +844,36 @@ public DBObject group( DBObject key , DBObject cond , DBObject initial , String
      */
     public DBObject group( DBObject key , DBObject cond , DBObject initial , String reduce , String finalize )
         throws MongoException {
+        GroupCommand cmd = new GroupCommand(this, key, cond, initial, reduce, finalize);        
+        return group( cmd );
+    }
 
-        BasicDBObject args  = new BasicDBObject();
-        args.put( "ns" , getName() );
-        args.put( "key" , key );
-        args.put( "cond" , cond );
-        args.put( "$reduce" , reduce );
-        args.put( "initial" , initial );
-        if ( finalize != null )
-            args.put( "finalize" , finalize );
-        
-        return group( args );
+    /**
+     * Applies a group operation
+     * @param cmd the group command
+     * @return
+     * @throws MongoException
+     * @see <a href="http://www.mongodb.org/display/DOCS/Aggregation">http://www.mongodb.org/display/DOCS/Aggregation</a>
+     */
+    public DBObject group( GroupCommand cmd ) {
+        CommandResult res =  _db.command( cmd.toDBObject() );
+        res.throwOnError();
+        return (DBObject)res.get( "retval" );
     }
 
+
     /**
+     * @deprecated prefer the {@link DBCollection#group(com.mongodb.GroupCommand)} which is more standard
      * Applies a group operation
-     * @param args object representing the parameters
+     * @param args object representing the arguments to the group function
      * @return
      * @throws MongoException
      * @see <a href="http://www.mongodb.org/display/DOCS/Aggregation">http://www.mongodb.org/display/DOCS/Aggregation</a>
      */
     public DBObject group( DBObject args )
         throws MongoException {
-        
-        args.put( "ns" , getName() );
-        
+        args.put( "ns" , getName() );  
         CommandResult res =  _db.command( new BasicDBObject( "group" , args ) );
-
         res.throwOnError();
         return (DBObject)res.get( "retval" );
     }

src/main/com/mongodb/GroupCommand.java

@@ -0,0 +1,51 @@
+/**
+ *      Copyright (C) 2008 10gen Inc.
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License");
+ *   you may not use this file except in compliance with the License.
+ *   You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *   distributed under the License is distributed on an "AS IS" BASIS,
+ *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *   See the License for the specific language governing permissions and
+ *   limitations under the License.
+ */
+package com.mongodb;
+
+/**
+ * This class groups the argument for a group operation and can build the underlying command object
+ * @dochub mapreduce
+ */
+public class GroupCommand {
+
+    public GroupCommand(DBCollection inputCollection, DBObject keys, DBObject condition, DBObject initial, String reduce, String finalize) {
+        this.input = inputCollection.getName();
+        this.keys = keys;
+        this.condition = condition;
+        this.initial = initial;
+        this.reduce = reduce;
+        this.finalize = finalize;
+    }
+
+    public DBObject toDBObject() {
+        BasicDBObject args  = new BasicDBObject();
+        args.put( "ns" , input );
+        args.put( "key" , keys );
+        args.put( "cond" , condition );
+        args.put( "$reduce" , reduce );
+        args.put( "initial" , initial );
+        if ( finalize != null )
+            args.put( "finalize" , finalize );
+        return new BasicDBObject( "group" , args );
+    }
+
+    String input;
+    DBObject keys;
+    DBObject condition;
+    DBObject initial;
+    String reduce;
+    String finalize;
+}

src/main/com/mongodb/MapReduceCommand.java

@@ -17,6 +17,10 @@
 
 package com.mongodb;
 
+/**
+ * This class groups the argument for a map/reduce operation and can build the underlying command object
+ * @dochub mapreduce
+ */
 public class MapReduceCommand {
 
     /**