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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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 org.apache.thrift.protocol;

import org.apache.thrift.TException;

/**
 * TMultiplexedProtocol is a protocol-independent concrete decorator that allows a
 * Thrift client to communicate with a multiplexing Thrift server, by prepending the service name to
 * the function name during function calls.
 *
 * NOTE: THIS IS NOT USED BY SERVERS. On the server, use {@link
 * org.apache.thrift.TMultiplexedProcessor TMultiplexedProcessor} to handle requests from a
 * multiplexing client.
 *
 * 
This example uses a single socket transport to invoke two services:
 *
 * 
{@code
 * TSocket transport = new TSocket("localhost", 9090);
 * transport.open();
 *
 * TBinaryProtocol protocol = new TBinaryProtocol(transport);
 *
 * TMultiplexedProtocol mp = new TMultiplexedProtocol(protocol, "Calculator");
 * Calculator.Client service = new Calculator.Client(mp);
 *
 * TMultiplexedProtocol mp2 = new TMultiplexedProtocol(protocol, "WeatherReport");
 * WeatherReport.Client service2 = new WeatherReport.Client(mp2);
 *
 * System.out.println(service.add(2,2));
 * System.out.println(service2.getTemperature());
 * }
 *
 * @see TProtocolDecorator
 */
public class TMultiplexedProtocol extends TProtocolDecorator {

  /** Used to delimit the service name from the function name */
  public static final String SEPARATOR = ":";

  private final String SERVICE_NAME;

  /**
   * Wrap the specified protocol, allowing it to be used to communicate with a multiplexing server.
   * The serviceName is required as it is prepended to the message header so that the
   * multiplexing server can broker the function call to the proper service.
   *
   * @param protocol Your communication protocol of choice, e.g. TBinaryProtocol.
   * @param serviceName The service name of the service communicating via this protocol.
   */
  public TMultiplexedProtocol(TProtocol protocol, String serviceName) {
    super(protocol);
    SERVICE_NAME = serviceName;
  }

  /**
   * Prepends the service name to the function name, separated by TMultiplexedProtocol.SEPARATOR.
   *
   * @param tMessage The original message.
   * @throws TException Passed through from wrapped TProtocol instance.
   */
  @Override
  public void writeMessageBegin(TMessage tMessage) throws TException {
    if (tMessage.type == TMessageType.CALL || tMessage.type == TMessageType.ONEWAY) {
      super.writeMessageBegin(
          new TMessage(SERVICE_NAME + SEPARATOR + tMessage.name, tMessage.type, tMessage.seqid));
    } else {
      super.writeMessageBegin(tMessage);
    }
  }
}