private void sendMessage(final CommandMessage message, final InternalConnection connection) {ByteBufferBsonOutput bsonOutput = new ByteBufferBsonOutput(connection);try {int documentPosition = message.encodeWithMetadata(bsonOutput).getFirstDocumentPosition();sendStartedEvent(connection, bsonOutput, message, documentPosition);connection.sendMessage(bsonOutput.getByteBuffers(), message.getId());} finally {bsonOutput.close();}}

        //注意：命令的key:value部分，value必须被[]或者{}或者''包裹。js的字符串支持单引号和双引号两种，这里使用单引号是为了避免在java中使用大量的 \　　　　　String command = "db.user.aggregate([{$group:{_id:'$name',count:{$sum:'$age'}}}])";BasicDBObject bson = new BasicDBObject();bson.put("$eval",command);Object object1 = mongoTemplate.getDb().doEval(command);Object object2 =  mongoTemplate.getDb().command(bson);Object object3 = mongoTemplate.getCollection("$cmd").findOne(bson);ScriptOperations operations = mongoTemplate.scriptOps();ExecutableMongoScript script = new ExecutableMongoScript(command);Object object4 = operations.execute(script);/*** call是调用system.js集合中方法的方法，传入参数是sysytem.js表中数据的主键值，* 可在mongo shell中天插入或者使用如下代码插入。* 插入一次后可直接使用*/
//        String command = "function(){return db.user.aggregate([{$group:{_id:'$name',count:{$sum:'$age'}}}])}";
//        NamedMongoScript namedMongoScript = new NamedMongoScript("user2",script);
//        operations.register(namedMongoScript);Object object5 = operations.call("user2");

private <T> List<T> executeFindMultiInternal(CollectionCallback<DBCursor> collectionCallback, CursorPreparer preparer,DbObjectCallback<T> objectCallback, String collectionName) {try {DBCursor cursor = null;try {cursor = collectionCallback.doInCollection(getAndPrepareCollection(getDb(), collectionName));if (preparer != null) {cursor = preparer.prepare(cursor);}List<T> result = new ArrayList<T>();while (cursor.hasNext()) {DBObject object = cursor.next();result.add(objectCallback.doWith(object));}return result;} finally {if (cursor != null) {cursor.close();}}} catch (RuntimeException e) {throw potentiallyConvertRuntimeException(e, exceptionTranslator);}}