1 // Protocol Buffers - Google's data interchange format 2 // Copyright 2008 Google Inc. All rights reserved. 3 // https://developers.google.com/protocol-buffers/ 4 // 5 // Redistribution and use in source and binary forms, with or without 6 // modification, are permitted provided that the following conditions are 7 // met: 8 // 9 // * Redistributions of source code must retain the above copyright 10 // notice, this list of conditions and the following disclaimer. 11 // * Redistributions in binary form must reproduce the above 12 // copyright notice, this list of conditions and the following disclaimer 13 // in the documentation and/or other materials provided with the 14 // distribution. 15 // * Neither the name of Google Inc. nor the names of its 16 // contributors may be used to endorse or promote products derived from 17 // this software without specific prior written permission. 18 // 19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31 package com.google.protobuf; 32 33 /** 34 * Abstract base interface for protocol-buffer-based RPC services. Services 35 * themselves are abstract classes (implemented either by servers or as 36 * stubs), but they subclass this base interface. The methods of this 37 * interface can be used to call the methods of the service without knowing 38 * its exact type at compile time (analogous to the Message interface). 39 * 40 * <p>Starting with version 2.3.0, RPC implementations should not try to build 41 * on this, but should instead provide code generator plugins which generate 42 * code specific to the particular RPC implementation. This way the generated 43 * code can be more appropriate for the implementation in use and can avoid 44 * unnecessary layers of indirection. 45 * 46 * @author kenton@google.com Kenton Varda 47 */ 48 public interface Service { 49 /** 50 * Get the {@code ServiceDescriptor} describing this service and its methods. 51 */ getDescriptorForType()52 Descriptors.ServiceDescriptor getDescriptorForType(); 53 54 /** 55 * <p>Call a method of the service specified by MethodDescriptor. This is 56 * normally implemented as a simple {@code switch()} that calls the standard 57 * definitions of the service's methods. 58 * 59 * <p>Preconditions: 60 * <ul> 61 * <li>{@code method.getService() == getDescriptorForType()} 62 * <li>{@code request} is of the exact same class as the object returned by 63 * {@code getRequestPrototype(method)}. 64 * <li>{@code controller} is of the correct type for the RPC implementation 65 * being used by this Service. For stubs, the "correct type" depends 66 * on the RpcChannel which the stub is using. Server-side Service 67 * implementations are expected to accept whatever type of 68 * {@code RpcController} the server-side RPC implementation uses. 69 * </ul> 70 * 71 * <p>Postconditions: 72 * <ul> 73 * <li>{@code done} will be called when the method is complete. This may be 74 * before {@code callMethod()} returns or it may be at some point in 75 * the future. 76 * <li>The parameter to {@code done} is the response. It must be of the 77 * exact same type as would be returned by 78 * {@code getResponsePrototype(method)}. 79 * <li>If the RPC failed, the parameter to {@code done} will be 80 * {@code null}. Further details about the failure can be found by 81 * querying {@code controller}. 82 * </ul> 83 */ callMethod(Descriptors.MethodDescriptor method, RpcController controller, Message request, RpcCallback<Message> done)84 void callMethod(Descriptors.MethodDescriptor method, 85 RpcController controller, 86 Message request, 87 RpcCallback<Message> done); 88 89 /** 90 * <p>{@code callMethod()} requires that the request passed in is of a 91 * particular subclass of {@code Message}. {@code getRequestPrototype()} 92 * gets the default instances of this type for a given method. You can then 93 * call {@code Message.newBuilderForType()} on this instance to 94 * construct a builder to build an object which you can then pass to 95 * {@code callMethod()}. 96 * 97 * <p>Example: 98 * <pre> 99 * MethodDescriptor method = 100 * service.getDescriptorForType().findMethodByName("Foo"); 101 * Message request = 102 * stub.getRequestPrototype(method).newBuilderForType() 103 * .mergeFrom(input).build(); 104 * service.callMethod(method, request, callback); 105 * </pre> 106 */ getRequestPrototype(Descriptors.MethodDescriptor method)107 Message getRequestPrototype(Descriptors.MethodDescriptor method); 108 109 /** 110 * Like {@code getRequestPrototype()}, but gets a prototype of the response 111 * message. {@code getResponsePrototype()} is generally not needed because 112 * the {@code Service} implementation constructs the response message itself, 113 * but it may be useful in some cases to know ahead of time what type of 114 * object will be returned. 115 */ getResponsePrototype(Descriptors.MethodDescriptor method)116 Message getResponsePrototype(Descriptors.MethodDescriptor method); 117 } 118