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 package filters;
19
20
21 import java.io.IOException;
22
23 import javax.servlet.Filter;
24 import javax.servlet.FilterChain;
25 import javax.servlet.FilterConfig;
26 import javax.servlet.ServletException;
27 import javax.servlet.ServletRequest;
28 import javax.servlet.ServletResponse;
29
30
31 /**
32 * Example filter that can be attached to either an individual servlet
33 * or to a URL pattern. This filter performs the following functions:
34 * <ul>
35 * <li>Attaches itself as a request attribute, under the attribute name
36 * defined by the value of the <code>attribute</code> initialization
37 * parameter.</li>
38 * <li>Calculates the number of milliseconds required to perform the
39 * servlet processing required by this request, including any
40 * subsequently defined filters, and logs the result to the servlet
41 * context log for this application.
42 * </ul>
43 *
44 * @author Craig McClanahan
45 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
46 */
47
48 public final class ExampleFilter implements Filter {
49
50 // ----------------------------------------------------- Instance Variables
51
52
53 /**
54 * The request attribute name under which we store a reference to ourself.
55 */
56 private String attribute = null;
57
58
59 /**
60 * The filter configuration object we are associated with. If this value
61 * is null, this filter instance is not currently configured.
62 */
63 private FilterConfig filterConfig = null;
64
65 // --------------------------------------------------------- Public Methods
66
67
68 /**
69 * Take this filter out of service.
70 */
71 public void destroy() {
72
73 this.attribute = null;
74 this.filterConfig = null;
75
76 }
77
78
79 /**
80 * Time the processing that is performed by all subsequent filters in the
81 * current filter stack, including the ultimately invoked servlet.
82 *
83 * @param request The servlet request we are processing
84 * @param result The servlet response we are creating
85 * @param chain The filter chain we are processing
86 * @throws IOException if an input/output error occurs
87 * @throws ServletException if a servlet error occurs
88 */
89 public void doFilter(ServletRequest request, ServletResponse response,
90 FilterChain chain)
91 throws IOException, ServletException {
92
93 // Store ourselves as a request attribute (if requested)
94 if (attribute != null)
95 request.setAttribute(attribute, this);
96
97 // Time and log the subsequent processing
98 long startTime = System.currentTimeMillis();
99 chain.doFilter(request, response);
100 long stopTime = System.currentTimeMillis();
101 filterConfig.getServletContext().log
102 (this.toString() + ": " + (stopTime - startTime) +
103 " milliseconds");
104
105 }
106
107
108 /**
109 * Place this filter into service.
110 *
111 * @param filterConfig The filter configuration object
112 */
113 public void init(FilterConfig filterConfig) throws ServletException {
114
115 this.filterConfig = filterConfig;
116 this.attribute = filterConfig.getInitParameter("attribute");
117
118 }
119
120
121 /**
122 * Return a String representation of this object.
123 */
124 public String toString() {
125
126 if (filterConfig == null)
127 return ("InvokerFilter()");
128 StringBuffer sb = new StringBuffer("InvokerFilter(");
129 sb.append(filterConfig);
130 sb.append(")");
131 return (sb.toString());
132
133 }
134
135
136 }
137