// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf/
//
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//
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package com.google.protobuf;
/**
* Abstract base interface for protocol-buffer-based RPC services. Services
* themselves are abstract classes (implemented either by servers or as
* stubs), but they subclass this base interface. The methods of this
* interface can be used to call the methods of the service without knowing
* its exact type at compile time (analogous to the Message interface).
*
* <p>Starting with version 2.3.0, RPC implementations should not try to build
* on this, but should instead provide code generator plugins which generate
* code specific to the particular RPC implementation. This way the generated
* code can be more appropriate for the implementation in use and can avoid
* unnecessary layers of indirection.
*
* @author kenton@google.com Kenton Varda
*/
public interface Service {
/**
* Get the {@code ServiceDescriptor} describing this service and its methods.
*/
Descriptors.ServiceDescriptor getDescriptorForType();
/**
* <p>Call a method of the service specified by MethodDescriptor. This is
* normally implemented as a simple {@code switch()} that calls the standard
* definitions of the service's methods.
*
* <p>Preconditions:
* <ul>
* <li>{@code method.getService() == getDescriptorForType()}
* <li>{@code request} is of the exact same class as the object returned by
* {@code getRequestPrototype(method)}.
* <li>{@code controller} is of the correct type for the RPC implementation
* being used by this Service. For stubs, the "correct type" depends
* on the RpcChannel which the stub is using. Server-side Service
* implementations are expected to accept whatever type of
* {@code RpcController} the server-side RPC implementation uses.
* </ul>
*
* <p>Postconditions:
* <ul>
* <li>{@code done} will be called when the method is complete. This may be
* before {@code callMethod()} returns or it may be at some point in
* the future.
* <li>The parameter to {@code done} is the response. It must be of the
* exact same type as would be returned by
* {@code getResponsePrototype(method)}.
* <li>If the RPC failed, the parameter to {@code done} will be
* {@code null}. Further details about the failure can be found by
* querying {@code controller}.
* </ul>
*/
void callMethod(Descriptors.MethodDescriptor method,
RpcController controller,
Message request,
RpcCallback<Message> done);
/**
* <p>{@code callMethod()} requires that the request passed in is of a
* particular subclass of {@code Message}. {@code getRequestPrototype()}
* gets the default instances of this type for a given method. You can then
* call {@code Message.newBuilderForType()} on this instance to
* construct a builder to build an object which you can then pass to
* {@code callMethod()}.
*
* <p>Example:
* <pre>
* MethodDescriptor method =
* service.getDescriptorForType().findMethodByName("Foo");
* Message request =
* stub.getRequestPrototype(method).newBuilderForType()
* .mergeFrom(input).build();
* service.callMethod(method, request, callback);
* </pre>
*/
Message getRequestPrototype(Descriptors.MethodDescriptor method);
/**
* Like {@code getRequestPrototype()}, but gets a prototype of the response
* message. {@code getResponsePrototype()} is generally not needed because
* the {@code Service} implementation constructs the response message itself,
* but it may be useful in some cases to know ahead of time what type of
* object will be returned.
*/
Message getResponsePrototype(Descriptors.MethodDescriptor method);
}