io.grpc.ClientInterceptor Maven / Gradle / Ivy
/*
* Copyright 2014 The gRPC Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.grpc;
import javax.annotation.concurrent.ThreadSafe;
/**
* Interface for intercepting outgoing calls before they are dispatched by a {@link Channel}.
*
* Implementers use this mechanism to add cross-cutting behavior to {@link Channel} and
* stub implementations. Common examples of such behavior include:
*
* - Logging and monitoring call behavior
* - Adding metadata for proxies to observe
* - Request and response rewriting
*
*
* Providing authentication credentials is better served by {@link
* CallCredentials}. But a {@code ClientInterceptor} could set the {@code
* CallCredentials} within the {@link CallOptions}.
*
*
The interceptor may be called for multiple {@link ClientCall calls} by one or more threads
* without completing the previous ones first. Refer to the
* {@link io.grpc.ClientCall.Listener ClientCall.Listener} docs for more details regarding thread
* safety of the returned listener.
*/
@ThreadSafe
public interface ClientInterceptor {
/**
* Intercept {@link ClientCall} creation by the {@code next} {@link Channel}.
*
*
Many variations of interception are possible. Complex implementations may return a wrapper
* around the result of {@code next.newCall()}, whereas a simpler implementation may just modify
* the header metadata prior to returning the result of {@code next.newCall()}.
*
*
{@code next.newCall()} must not be called under a different {@link Context}
* other than the current {@code Context}. The outcome of such usage is undefined and may cause
* memory leak due to unbounded chain of {@code Context}s.
*
* @param method the remote method to be called.
* @param callOptions the runtime options to be applied to this call.
* @param next the channel which is being intercepted.
* @return the call object for the remote operation, never {@code null}.
*/
ClientCall interceptCall(
MethodDescriptor method, CallOptions callOptions, Channel next);
}