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1   //
2   //  ========================================================================
3   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
4   //  ------------------------------------------------------------------------
5   //  All rights reserved. This program and the accompanying materials
6   //  are made available under the terms of the Eclipse Public License v1.0
7   //  and Apache License v2.0 which accompanies this distribution.
8   //
9   //      The Eclipse Public License is available at
10  //      http://www.eclipse.org/legal/epl-v10.html
11  //
12  //      The Apache License v2.0 is available at
13  //      http://www.opensource.org/licenses/apache2.0.php
14  //
15  //  You may elect to redistribute this code under either of these licenses.
16  //  ========================================================================
17  //
18  
19  package org.eclipse.jetty.server.handler;
20  
21  import java.io.IOException;
22  
23  import javax.servlet.AsyncContext;
24  import javax.servlet.DispatcherType;
25  import javax.servlet.ServletException;
26  import javax.servlet.http.HttpServletRequest;
27  import javax.servlet.http.HttpServletResponse;
28  
29  import org.eclipse.jetty.server.Request;
30  
31  
32  /* ------------------------------------------------------------ */
33  /** A handler wrapper that provides the framework to asynchronously
34   * delay the handling of a request.  While it uses standard servlet 
35   * API for asynchronous servlets, it adjusts the dispatch type of the 
36   * request so that it does not appear to be asynchronous during the
37   * delayed dispatch.
38   * 
39   */
40  public class AsyncDelayHandler extends HandlerWrapper
41  {
42      public final static String AHW_ATTR = "o.e.j.s.h.AsyncHandlerWrapper";
43  
44      /* ------------------------------------------------------------ */
45      @Override
46      public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
47      {
48          if (!isStarted() || _handler==null)
49              return;
50          
51          // Get the dispatcher types
52          DispatcherType ctype = baseRequest.getDispatcherType();
53          DispatcherType dtype = (DispatcherType)baseRequest.getAttribute(AHW_ATTR);
54          Object async_context_path=null;
55          Object async_path_info=null;
56          Object async_query_string=null;
57          Object async_request_uri=null;
58          Object async_servlet_path=null;
59          
60          // Is this request a restarted one?
61          boolean restart=false;
62          if (dtype!=null)
63          {
64              // fake the dispatch type to the original
65              baseRequest.setAttribute(AHW_ATTR,null);
66              baseRequest.setDispatcherType(dtype);
67              restart=true;
68              
69              async_context_path=baseRequest.getAttribute(AsyncContext.ASYNC_CONTEXT_PATH);
70              baseRequest.setAttribute(AsyncContext.ASYNC_CONTEXT_PATH,null);
71              async_path_info=baseRequest.getAttribute(AsyncContext.ASYNC_PATH_INFO);
72              baseRequest.setAttribute(AsyncContext.ASYNC_PATH_INFO,null);
73              async_query_string=baseRequest.getAttribute(AsyncContext.ASYNC_QUERY_STRING);
74              baseRequest.setAttribute(AsyncContext.ASYNC_QUERY_STRING,null);
75              async_request_uri=baseRequest.getAttribute(AsyncContext.ASYNC_REQUEST_URI);
76              baseRequest.setAttribute(AsyncContext.ASYNC_REQUEST_URI,null);
77              async_servlet_path=baseRequest.getAttribute(AsyncContext.ASYNC_SERVLET_PATH);
78              baseRequest.setAttribute(AsyncContext.ASYNC_SERVLET_PATH,null);
79          }
80          
81          // Should we handle this request now?
82          if (!startHandling(baseRequest,restart))
83          {
84              // No, so go async and remember dispatch type
85              AsyncContext context = baseRequest.startAsync();
86              baseRequest.setAttribute(AHW_ATTR,ctype);
87  
88              delayHandling(baseRequest, context);
89              return;
90          }
91  
92          // Handle the request
93          try
94          {
95              _handler.handle(target,baseRequest, request, response);
96          }
97          finally
98          {
99              if(restart)
100             {
101                 // reset the request
102                 baseRequest.setDispatcherType(ctype);
103                 baseRequest.setAttribute(AsyncContext.ASYNC_CONTEXT_PATH,async_context_path);
104                 baseRequest.setAttribute(AsyncContext.ASYNC_PATH_INFO,async_path_info);
105                 baseRequest.setAttribute(AsyncContext.ASYNC_QUERY_STRING,async_query_string);
106                 baseRequest.setAttribute(AsyncContext.ASYNC_REQUEST_URI,async_request_uri);
107                 baseRequest.setAttribute(AsyncContext.ASYNC_SERVLET_PATH,async_servlet_path);
108             }
109             
110             // signal the request is leaving the handler
111             endHandling(baseRequest);
112         }
113         
114     }
115     
116     /* ------------------------------------------------------------ */
117     /** Called to indicate that a request has been presented for handling
118      * @param request The request to handle
119      * @param restart True if this request is being restarted after a delay
120      * @return True if the request should be handled now
121      */
122     protected boolean startHandling(Request request, boolean restart)
123     {
124         return true;
125     }
126 
127     /* ------------------------------------------------------------ */
128     /** Called to indicate that a requests handling is being delayed/
129      * The implementation should arrange for context.dispatch() to be
130      * called when the request should be handled.  It may also set
131      * timeouts on the context. 
132      * 
133      * @param request The request to be delayed
134      * @param context The AsyncContext of the delayed request
135      */
136     protected void delayHandling(Request request,AsyncContext context)
137     {
138         context.dispatch();
139     }
140     
141     /* ------------------------------------------------------------ */
142     /** Called to indicated the handling of the request is ending.
143      * This is only the end of the current dispatch of the request and
144      * if the request is asynchronous, it may be handled again.
145      * @param request The request
146      */
147     protected void endHandling(Request request)
148     {
149         
150     }
151     
152     
153 }