CometServlet


1   /*
2    * Copyright 2006 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * 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,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  
18  package org.apache.catalina.servlets;
19  
20  
21  import java.io.IOException  ;
22  import java.io.InputStream  ;
23  
24  import javax.servlet.ServletException  ;
25  import javax.servlet.http.HttpServlet  ;
26  import javax.servlet.http.HttpServletRequest  ;
27  import javax.servlet.http.HttpServletResponse  ;
28  
29  import org.apache.catalina.CometProcessor;
30  
31  
32  /**
33   * Helper class to implement Comet functionality.
34   */
35  public abstract class CometServlet
36      extends HttpServlet   implements CometProcessor {
37  
38      public void begin(HttpServletRequest   request, HttpServletResponse   response)
39          throws IOException  , ServletException   {
40          request.setAttribute("org.apache.tomcat.comet", Boolean.TRUE);
41      }
42      
43      public void end(HttpServletRequest   request, HttpServletResponse   response)
44          throws IOException  , ServletException   {
45          request.removeAttribute("org.apache.tomcat.comet");
46      }
47      
48      public void error(HttpServletRequest   request, HttpServletResponse   response)
49          throws IOException  , ServletException   {
50          end(request, response);
51      }
52      
53      public boolean read(HttpServletRequest   request, HttpServletResponse   response)
54          throws IOException  , ServletException   {
55          InputStream   is = request.getInputStream();
56          byte[] buf = new byte[512];
57          do {
58              int n = is.read(buf);
59              if (n > 0) {
60                  // Do something with the data
61              } else if (n < 0) {
62                  return false;
63              }
64          } while (is.available() > 0);
65          return true;
66      }
67  
68      protected void service(HttpServletRequest   request, HttpServletResponse   response)
69          throws IOException  , ServletException   {
70          
71          if (request.getAttribute("org.apache.tomcat.comet.support") == Boolean.TRUE) {
72              begin(request, response);
73          } else {
74              // No Comet support: regular servlet handling
75              begin(request, response);
76              boolean error = true;
77              try {
78                  // Loop reading data
79                  while (read(request, response));
80                  error = false;
81              } finally {
82                  if (error) {
83                      error(request, response);
84                  } else {
85                      end(request, response);
86                  }
87              }
88          }
89      }
90      
91      public void setTimeout(HttpServletRequest   request, HttpServletResponse   response, int timeout)
92          throws IOException  , ServletException  , UnsupportedOperationException   {
93          if (request.getAttribute("org.apache.tomcat.comet.timeout.support") == Boolean.TRUE) {
94              request.setAttribute("org.apache.tomcat.comet.timeout",new Integer  (timeout));
95          } else {
96              throw new UnsupportedOperationException  ();
97          }
98      }
99  
100 
101 }
102
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