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 package filters;
019
020
021 import java.io.IOException;
022
023 import javax.servlet.Filter;
024 import javax.servlet.FilterChain;
025 import javax.servlet.FilterConfig;
026 import javax.servlet.ServletException;
027 import javax.servlet.ServletRequest;
028 import javax.servlet.ServletResponse;
029
030
031 /**
032 * Example filter that can be attached to either an individual servlet
033 * or to a URL pattern. This filter performs the following functions:
034 * <ul>
035 * <li>Attaches itself as a request attribute, under the attribute name
036 * defined by the value of the <code>attribute</code> initialization
037 * parameter.</li>
038 * <li>Calculates the number of milliseconds required to perform the
039 * servlet processing required by this request, including any
040 * subsequently defined filters, and logs the result to the servlet
041 * context log for this application.
042 * </ul>
043 *
044 * @author Craig McClanahan
045 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
046 */
047
048 public final class ExampleFilter implements Filter {
049
050 // ----------------------------------------------------- Instance Variables
051
052
053 /**
054 * The request attribute name under which we store a reference to ourself.
055 */
056 private String attribute = null;
057
058
059 /**
060 * The filter configuration object we are associated with. If this value
061 * is null, this filter instance is not currently configured.
062 */
063 private FilterConfig filterConfig = null;
064
065 // --------------------------------------------------------- Public Methods
066
067
068 /**
069 * Take this filter out of service.
070 */
071 public void destroy() {
072
073 this.attribute = null;
074 this.filterConfig = null;
075
076 }
077
078
079 /**
080 * Time the processing that is performed by all subsequent filters in the
081 * current filter stack, including the ultimately invoked servlet.
082 *
083 * @param request The servlet request we are processing
084 * @param result The servlet response we are creating
085 * @param chain The filter chain we are processing
086 * @throws IOException if an input/output error occurs
087 * @throws ServletException if a servlet error occurs
088 */
089 public void doFilter(ServletRequest request, ServletResponse response,
090 FilterChain chain)
091 throws IOException, ServletException {
092
093 // Store ourselves as a request attribute (if requested)
094 if (attribute != null)
095 request.setAttribute(attribute, this);
096
097 // Time and log the subsequent processing
098 long startTime = System.currentTimeMillis();
099 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