001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018
019 package filters;
020
021
022 import java.io.IOException;
023
024 import javax.servlet.Filter;
025 import javax.servlet.FilterChain;
026 import javax.servlet.FilterConfig;
027 import javax.servlet.ServletException;
028 import javax.servlet.ServletRequest;
029 import javax.servlet.ServletResponse;
030
031
032 /**
033 * Example filter that can be attached to either an individual servlet
034 * or to a URL pattern. This filter performs the following functions:
035 * <ul>
036 * <li>Attaches itself as a request attribute, under the attribute name
037 * defined by the value of the <code>attribute</code> initialization
038 * parameter.</li>
039 * <li>Calculates the number of milliseconds required to perform the
040 * servlet processing required by this request, including any
041 * subsequently defined filters, and logs the result to the servlet
042 * context log for this application.
043 * </ul>
044 *
045 * @author Craig McClanahan
046 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
047 */
048
049 public final class ExampleFilter implements Filter {
050
051 // ----------------------------------------------------- Instance Variables
052
053
054 /**
055 * The request attribute name under which we store a reference to ourself.
056 */
057 private String attribute = null;
058
059
060 /**
061 * The filter configuration object we are associated with. If this value
062 * is null, this filter instance is not currently configured.
063 */
064 private FilterConfig filterConfig = null;
065
066 // --------------------------------------------------------- Public Methods
067
068
069 /**
070 * Take this filter out of service.
071 */
072 public void destroy() {
073
074 this.attribute = null;
075 this.filterConfig = null;
076
077 }
078
079
080 /**
081 * Time the processing that is performed by all subsequent filters in the
082 * current filter stack, including the ultimately invoked servlet.
083 *
084 * @param request The servlet request we are processing
085 * @param result The servlet response we are creating
086 * @param chain The filter chain we are processing
087 * @throws IOException if an input/output error occurs
088 * @throws ServletException if a servlet error occurs
089 */
090 public void doFilter(ServletRequest request, ServletResponse response,
091 FilterChain chain)
092 throws IOException, ServletException {
093
094 // Store ourselves as a request attribute (if requested)
095 if (attribute != null)
096 request.setAttribute(attribute, this);
097
098 // Time and log the subsequent processing
099 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