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   /*
    * Copyright 2013 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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.netty.example.http.helloworld;
  
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.codec.http.DefaultFullHttpResponse;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.HttpObject;
  import io.netty.handler.codec.http.HttpRequest;
  import io.netty.handler.codec.http.HttpUtil;
  
  import static io.netty.handler.codec.http.HttpHeaderNames.CONNECTION;
  import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_LENGTH;
  import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
  import static io.netty.handler.codec.http.HttpHeaderValues.CLOSE;
  import static io.netty.handler.codec.http.HttpHeaderValues.KEEP_ALIVE;
  import static io.netty.handler.codec.http.HttpHeaderValues.TEXT_PLAIN;
  import static io.netty.handler.codec.http.HttpResponseStatus.OK;
  
  public class HttpHelloWorldServerHandler extends SimpleChannelInboundHandler<HttpObject> {
      private static final byte[] CONTENT = { 'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd' };
  
      @Override
      public void channelReadComplete(ChannelHandlerContext ctx) {
          ctx.flush();
      }
  
      @Override
      public void channelRead0(ChannelHandlerContext ctx, HttpObject msg) {
          if (msg instanceof HttpRequest) {
              HttpRequest req = (HttpRequest) msg;
  
              boolean keepAlive = HttpUtil.isKeepAlive(req);
              FullHttpResponse response = new DefaultFullHttpResponse(req.protocolVersion(), OK,
                                                                      Unpooled.wrappedBuffer(CONTENT));
              response.headers()
                      .set(CONTENT_TYPE, TEXT_PLAIN)
                      .setInt(CONTENT_LENGTH, response.content().readableBytes());
  
              if (keepAlive) {
                  if (!req.protocolVersion().isKeepAliveDefault()) {
                      response.headers().set(CONNECTION, KEEP_ALIVE);
                  }
              } else {
                  // Tell the client we're going to close the connection.
                  response.headers().set(CONNECTION, CLOSE);
              }
  
              ChannelFuture f = ctx.write(response);
  
              if (!keepAlive) {
                  f.addListener(ChannelFutureListener.CLOSE);
              }
          }
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
          cause.printStackTrace();
          ctx.close();
      }
  }