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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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();
/**
* 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);
/**
* {@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);
}
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