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Java > Open Source Codes > example > PeriodicTaskFilter


1 package example;
2
3 import java.io.IOException JavaDoc;
4
5 import java.util.logging.Level JavaDoc;
6 import java.util.logging.Logger JavaDoc;
7
8 import javax.servlet.*;
9 import javax.servlet.http.*;
10
11 /**
12  * Filter to show a maintenance page if the MaintenanceRunner is active.
13  *
14  * <h3>init parameters</h3>
15  * <dl>
16  * <dt>url
17  * <dd>The url to forward to when active, if not set then a 503
18  * (SERVICE_UNAVAILABLE) error code is returned.
19  * <dt>min-estimated-time
20  * <dd>The minimum amount of time in seconds for an estimate of when the task
21  * will complete, default is 5 seconds.
22  * </dl>
23  */
24 public class PeriodicTaskFilter implements Filter {
25   static protected final Logger JavaDoc log =
26     Logger.getLogger(PeriodicTaskFilter.class.getName());
27
28   private String JavaDoc _url = null;
29   private int _minEstimatedTime = 5;;
30
31   private PeriodicTask _periodicTask;
32
33   public PeriodicTaskFilter()
34   {
35   }
36
37   public void setPeriodicTask(PeriodicTask periodicTask)
38   {
39     _periodicTask = periodicTask;
40   }
41
42   /**
43    * The url to forward to when active, if not set then a 503
44    * (SERVICE_UNAVAILABLE) error code is returned.
45    */
46   public void setUrl(String JavaDoc url)
47   {
48     _url = url;
49   }
50
51   /**
52    * The minimum amount of time in seconds for an estimate of when the task
53    * will complete, default is 5 seconds.
54    */
55   public void setMinEstimatedTime(int seconds)
56   {
57     _minEstimatedTime = seconds;
58   }
59
60   public void init(FilterConfig filterConfig)
61     throws ServletException
62   {
63     String JavaDoc p;
64
65     p = filterConfig.getInitParameter("url");
66     if (p != null)
67       setUrl(p);
68
69     p = filterConfig.getInitParameter("min-estimated-time");
70     if (p != null)
71       setMinEstimatedTime(Integer.parseInt(p));
72
73     if (_periodicTask == null)
74       throw new ServletException("`period-task' is required");
75   }
76
77   public void doFilter(ServletRequest request,
78       ServletResponse response,
79       FilterChain chain)
80     throws ServletException, IOException JavaDoc
81   {
82     if (_periodicTask.isActive()) {
83       dispatch( (HttpServletRequest) request, (HttpServletResponse) response);
84     }
85     else {
86       chain.doFilter(request,response);
87     }
88   }
89
90   /**
91    * Disptach to a page that shows a "temporarily unavailable" message, or
92    * respond with 503.
93    */
94   protected void dispatch(HttpServletRequest request, HttpServletResponse response)
95     throws ServletException, IOException JavaDoc
96   {
97     long remaining = _periodicTask.getEstimatedTimeRemaining();
98
99     // convert to seconds
100 remaining = ( (1000L + remaining) / 1000L ) - 1;
101
102     if (remaining < _minEstimatedTime)
103       remaining = _minEstimatedTime;
104
105     response.addHeader("Cache-Control", "max-age=" + remaining);
106     response.addHeader("refresh", String.valueOf(remaining));
107
108     if (_url != null)
109       request.getRequestDispatcher(_url).forward(request,response);
110     else
111       response.sendError(response.SC_SERVICE_UNAVAILABLE);
112   }
113
114   public void destroy()
115   {
116   }
117 }
118
119
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