View Javadoc
1   /*
2    * Copyright 2017 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. 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, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.codec.http;
17  
18  import io.netty.buffer.Unpooled;
19  import io.netty.channel.ChannelFutureListener;
20  import io.netty.channel.ChannelHandlerContext;
21  import io.netty.channel.ChannelInboundHandlerAdapter;
22  import io.netty.util.ReferenceCountUtil;
23  
24  import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_LENGTH;
25  import static io.netty.handler.codec.http.HttpResponseStatus.CONTINUE;
26  import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
27  
28  /**
29   * Sends a <a href="https://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.2.3">100 CONTINUE</a>
30   * {@link HttpResponse} to {@link HttpRequest}s which contain a 'expect: 100-continue' header. It
31   * should only be used for applications which do <b>not</b> install the {@link HttpObjectAggregator}.
32   * <p>
33   * By default it accepts all expectations.
34   * <p>
35   * Since {@link HttpServerExpectContinueHandler} expects {@link HttpRequest}s it should be added after {@link
36   * HttpServerCodec} but before any other handlers that might send a {@link HttpResponse}. <blockquote>
37   * <pre>
38   *  {@link io.netty.channel.ChannelPipeline} p = ...;
39   *  ...
40   *  p.addLast("serverCodec", new {@link HttpServerCodec}());
41   *  p.addLast("respondExpectContinue", <b>new {@link HttpServerExpectContinueHandler}()</b>);
42   *  ...
43   *  p.addLast("handler", new HttpRequestHandler());
44   *  </pre>
45   * </blockquote>
46   */
47  public class HttpServerExpectContinueHandler extends ChannelInboundHandlerAdapter {
48  
49      private static final FullHttpResponse EXPECTATION_FAILED = new DefaultFullHttpResponse(
50              HTTP_1_1, HttpResponseStatus.EXPECTATION_FAILED, Unpooled.EMPTY_BUFFER);
51  
52      private static final FullHttpResponse ACCEPT = new DefaultFullHttpResponse(
53              HTTP_1_1, CONTINUE, Unpooled.EMPTY_BUFFER);
54  
55      static {
56          EXPECTATION_FAILED.headers().set(CONTENT_LENGTH, 0);
57          ACCEPT.headers().set(CONTENT_LENGTH, 0);
58      }
59  
60      /**
61       * Produces a {@link HttpResponse} for {@link HttpRequest}s which define an expectation. Returns {@code null} if the
62       * request should be rejected. See {@link #rejectResponse(HttpRequest)}.
63       */
64      protected HttpResponse acceptMessage(@SuppressWarnings("unused") HttpRequest request) {
65          return ACCEPT.retainedDuplicate();
66      }
67  
68      /**
69       * Returns the appropriate 4XX {@link HttpResponse} for the given {@link HttpRequest}.
70       */
71      protected HttpResponse rejectResponse(@SuppressWarnings("unused") HttpRequest request) {
72          return EXPECTATION_FAILED.retainedDuplicate();
73      }
74  
75      @Override
76      public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
77          if (msg instanceof HttpRequest) {
78              HttpRequest req = (HttpRequest) msg;
79  
80              if (HttpUtil.is100ContinueExpected(req)) {
81                  HttpResponse accept = acceptMessage(req);
82  
83                  if (accept == null) {
84                      // the expectation failed so we refuse the request.
85                      HttpResponse rejection = rejectResponse(req);
86                      ReferenceCountUtil.release(msg);
87                      ctx.writeAndFlush(rejection).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
88                      return;
89                  }
90  
91                  ctx.writeAndFlush(accept).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
92                  req.headers().remove(HttpHeaderNames.EXPECT);
93              }
94          }
95          super.channelRead(ctx, msg);
96      }
97  }