1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18
19 package filters;
20
21
22 import java.io.IOException;
23
24 import javax.servlet.Filter;
25 import javax.servlet.FilterChain;
26 import javax.servlet.FilterConfig;
27 import javax.servlet.ServletException;
28 import javax.servlet.ServletRequest;
29 import javax.servlet.ServletResponse;
30
31
32 /**
33 * Example filter that can be attached to either an individual servlet
34 * or to a URL pattern. This filter performs the following functions:
35 * <ul>
36 * <li>Attaches itself as a request attribute, under the attribute name
37 * defined by the value of the <code>attribute</code> initialization
38 * parameter.</li>
39 * <li>Calculates the number of milliseconds required to perform the
40 * servlet processing required by this request, including any
41 * subsequently defined filters, and logs the result to the servlet
42 * context log for this application.
43 * </ul>
44 *
45 * @author Craig McClanahan
46 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
47 */
48
49 public final class ExampleFilter implements Filter {
50
51 // ----------------------------------------------------- Instance Variables
52
53
54 /**
55 * The request attribute name under which we store a reference to ourself.
56 */
57 private String attribute = null;
58
59
60 /**
61 * The filter configuration object we are associated with. If this value
62 * is null, this filter instance is not currently configured.
63 */
64 private FilterConfig filterConfig = null;
65
66 // --------------------------------------------------------- Public Methods
67
68
69 /**
70 * Take this filter out of service.
71 */
72 public void destroy() {
73
74 this.attribute = null;
75 this.filterConfig = null;
76
77 }
78
79
80 /**
81 * Time the processing that is performed by all subsequent filters in the
82 * current filter stack, including the ultimately invoked servlet.
83 *
84 * @param request The servlet request we are processing
85 * @param result The servlet response we are creating
86 * @param chain The filter chain we are processing
87 * @throws IOException if an input/output error occurs
88 * @throws ServletException if a servlet error occurs
89 */
90 public void doFilter(ServletRequest request, ServletResponse response,
91 FilterChain chain)
92 throws IOException, ServletException {
93
94 // Store ourselves as a request attribute (if requested)
95 if (attribute != null)
96 request.setAttribute(attribute, this);
97
98 // Time and log the subsequent processing
99 long startTime = System.currentTimeMillis();
100 chain.doFilter(request, response);
101 long stopTime = System.currentTimeMillis();
102 filterConfig.getServletContext().log
103 (this.toString() + ": " + (stopTime - startTime) +
104 " milliseconds");
105
106 }
107
108
109 /**
110 * Place this filter into service.
111 *
112 * @param filterConfig The filter configuration object
113 */
114 public void init(FilterConfig filterConfig) throws ServletException {
115
116 this.filterConfig = filterConfig;
117 this.attribute = filterConfig.getInitParameter("attribute");
118
119 }
120
121
122 /**
123 * Return a String representation of this object.
124 */
125 public String toString() {
126
127 if (filterConfig == null)
128 return ("InvokerFilter()");
129 StringBuffer sb = new StringBuffer("InvokerFilter(");
130 sb.append(filterConfig);
131 sb.append(")");
132 return (sb.toString());
133
134 }
135
136
137 }
138