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   /*
    * Copyright 2014 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.http2.helloworld.server;
  
  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.HttpResponseStatus.CONTINUE;
  import static io.netty.handler.codec.http.HttpResponseStatus.OK;
  import static io.netty.handler.codec.http.HttpVersion.HTTP_1_0;
  import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufUtil;
  import io.netty.buffer.Unpooled;
  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.FullHttpRequest;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.HttpUtil;
  
  /**
   * HTTP handler that responds with a "Hello World"
   */
  public class HelloWorldHttp1Handler extends SimpleChannelInboundHandler<FullHttpRequest> {
      private final String establishApproach;
  
      public HelloWorldHttp1Handler(String establishApproach) {
          this.establishApproach = checkNotNull(establishApproach, "establishApproach");
      }
  
      @Override
      public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest req) throws Exception {
          if (HttpUtil.is100ContinueExpected(req)) {
              ctx.write(new DefaultFullHttpResponse(HTTP_1_1, CONTINUE, Unpooled.EMPTY_BUFFER));
          }
  
          ByteBuf content = ctx.alloc().buffer();
          content.writeBytes(HelloWorldHttp2Handler.RESPONSE_BYTES.duplicate());
          ByteBufUtil.writeAscii(content, " - via " + req.protocolVersion() + " (" + establishApproach + ")");
  
          FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, content);
          response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");
          response.headers().setInt(CONTENT_LENGTH, response.content().readableBytes());
  
          boolean keepAlive = HttpUtil.isKeepAlive(req);
          if (keepAlive) {
              if (req.protocolVersion().equals(HTTP_1_0)) {
                  response.headers().set(CONNECTION, KEEP_ALIVE);
              }
              ctx.write(response);
          } else {
              // Tell the client we're going to close the connection.
              response.headers().set(CONNECTION, CLOSE);
              ctx.write(response).addListener(ChannelFutureListener.CLOSE);
          }
      }
  
      @Override
      public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
          ctx.flush();
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
          cause.printStackTrace();
          ctx.close();
      }
  }