examples/src/main/java/io/grpc/examples/header/HeaderServerInterceptor.java

/*
 * Copyright 2015 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.examples.header;

import com.google.common.annotations.VisibleForTesting;
import io.grpc.ForwardingServerCall.SimpleForwardingServerCall;
import io.grpc.Metadata;
import io.grpc.ServerCall;
import io.grpc.ServerCallHandler;
import io.grpc.ServerInterceptor;
import java.util.logging.Logger;

/**
 * A interceptor to handle server header.
 */
public class HeaderServerInterceptor implements ServerInterceptor {

  private static final Logger logger = Logger.getLogger(HeaderServerInterceptor.class.getName());

  @VisibleForTesting
  static final Metadata.Key<String> CUSTOM_HEADER_KEY =
      Metadata.Key.of("custom_server_header_key", Metadata.ASCII_STRING_MARSHALLER);


  @Override
  public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
      ServerCall<ReqT, RespT> call,
      final Metadata requestHeaders,
      ServerCallHandler<ReqT, RespT> next) {
    logger.info("header received from client:" + requestHeaders);
    return next.startCall(new SimpleForwardingServerCall<ReqT, RespT>(call) {
      @Override
      public void sendHeaders(Metadata responseHeaders) {
        responseHeaders.put(CUSTOM_HEADER_KEY, "customRespondValue");
        super.sendHeaders(responseHeaders);
      }
    }, requestHeaders);
  }
}