1 /** 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 package org.apache.hadoop.ipc; 19 20 import java.lang.annotation.Retention; 21 import java.lang.annotation.RetentionPolicy; 22 23 24 /** 25 * The protocol name that is used when a client and server connect. 26 * By default the class name of the protocol interface is the protocol name. 27 * 28 * Why override the default name (i.e. the class name)? 29 * One use case overriding the default name (i.e. the class name) is when 30 * there are multiple implementations of the same protocol, each with say a 31 * different version/serialization. 32 * In Hadoop this is used to allow multiple server and client adapters 33 * for different versions of the same protocol service. 34 */ 35 @Retention(RetentionPolicy.RUNTIME) 36 public @interface ProtocolInfo { protocolName()37 String protocolName(); // the name of the protocol (i.e. rpc service) protocolVersion()38 long protocolVersion() default -1; // default means not defined use old way 39 } 40