1 // Protocol Buffers - Google's data interchange format
2 // Copyright 2008 Google Inc. All rights reserved.
3 // http://code.google.com/p/protobuf/
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31 package com.google.protobuf;
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).
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.
46 * @author kenton@google.com Kenton Varda
48 public interface Service {
50 * Get the {@code ServiceDescriptor} describing this service and its methods.
52 Descriptors.ServiceDescriptor getDescriptorForType();
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.
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.
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
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}.
84 void callMethod(Descriptors.MethodDescriptor method,
85 RpcController controller,
87 RpcCallback<Message> done);
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()}.
99 * MethodDescriptor method =
100 * service.getDescriptorForType().findMethodByName("Foo");
102 * stub.getRequestPrototype(method).newBuilderForType()
103 * .mergeFrom(input).build();
104 * service.callMethod(method, request, callback);
107 Message getRequestPrototype(Descriptors.MethodDescriptor method);
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.
116 Message getResponsePrototype(Descriptors.MethodDescriptor method);