1 /* 2 * Copyright 2014 The gRPC Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package io.grpc; 18 19 import javax.annotation.concurrent.ThreadSafe; 20 21 /** 22 * Interface for intercepting incoming calls before that are dispatched by 23 * {@link ServerCallHandler}. 24 * 25 * <p>Implementers use this mechanism to add cross-cutting behavior to server-side calls. Common 26 * example of such behavior include: 27 * <ul> 28 * <li>Enforcing valid authentication credentials</li> 29 * <li>Logging and monitoring call behavior</li> 30 * <li>Delegating calls to other servers</li> 31 * </ul> 32 * 33 * <p>The interceptor may be called for multiple {@link ServerCall calls} by one or more threads 34 * without completing the previous ones first. Refer to the 35 * {@link io.grpc.ServerCall.Listener ServerCall.Listener} docs for more details regarding thread 36 * safety of the returned listener. 37 */ 38 @ThreadSafe 39 public interface ServerInterceptor { 40 /** 41 * Intercept {@link ServerCall} dispatch by the {@code next} {@link ServerCallHandler}. General 42 * semantics of {@link ServerCallHandler#startCall} apply and the returned 43 * {@link io.grpc.ServerCall.Listener} must not be {@code null}. 44 * 45 * <p>If the implementation throws an exception, {@code call} will be closed with an error. 46 * Implementations must not throw an exception if they started processing that may use {@code 47 * call} on another thread. 48 * 49 * @param call object to receive response messages 50 * @param headers which can contain extra call metadata from {@link ClientCall#start}, 51 * e.g. authentication credentials. 52 * @param next next processor in the interceptor chain 53 * @return listener for processing incoming messages for {@code call}, never {@code null}. 54 */ interceptCall( ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next)55 <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall( 56 ServerCall<ReqT, RespT> call, 57 Metadata headers, 58 ServerCallHandler<ReqT, RespT> next); 59 } 60