001 /*
002 * Copyright 2004 The Apache Software Foundation
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package filters;
018
019
020 import java.io.IOException;
021 import javax.servlet.Filter;
022 import javax.servlet.FilterChain;
023 import javax.servlet.FilterConfig;
024 import javax.servlet.ServletContext;
025 import javax.servlet.ServletException;
026 import javax.servlet.ServletRequest;
027 import javax.servlet.ServletResponse;
028
029
030 /**
031 * Example filter that can be attached to either an individual servlet
032 * or to a URL pattern. This filter performs the following functions:
033 * <ul>
034 * <li>Attaches itself as a request attribute, under the attribute name
035 * defined by the value of the <code>attribute</code> initialization
036 * parameter.</li>
037 * <li>Calculates the number of milliseconds required to perform the
038 * servlet processing required by this request, including any
039 * subsequently defined filters, and logs the result to the servlet
040 * context log for this application.
041 * </ul>
042 *
043 * @author Craig McClanahan
044 * @version $Revision: 267129 $ $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $
045 */
046
047 public final class ExampleFilter implements Filter {
048
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
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 *
088 * @exception IOException if an input/output error occurs
089 * @exception ServletException if a servlet error occurs
090 */
091 public void doFilter(ServletRequest request, ServletResponse response,
092 FilterChain chain)
093 throws IOException, ServletException {
094
095 // Store ourselves as a request attribute (if requested)
096 if (attribute != null)
097 request.setAttribute(attribute, this);
098
099 // Time and log the subsequent processing
100 long startTime = System.currentTimeMillis();
101 chain.doFilter(request, response);
102 long stopTime = System.currentTimeMillis();
103 filterConfig.getServletContext().log
104 (this.toString() + ": " + (stopTime - startTime) +
105 " milliseconds");
106
107 }
108
109
110 /**
111 * Place this filter into service.
112 *
113 * @param filterConfig The filter configuration object
114 */
115 public void init(FilterConfig filterConfig) throws ServletException {
116
117 this.filterConfig = filterConfig;
118 this.attribute = filterConfig.getInitParameter("attribute");
119
120 }
121
122
123 /**
124 * Return a String representation of this object.
125 */
126 public String toString() {
127
128 if (filterConfig == null)
129 return ("InvokerFilter()");
130 StringBuffer sb = new StringBuffer("InvokerFilter(");
131 sb.append(filterConfig);
132 sb.append(")");
133 return (sb.toString());
134
135 }
136
137
138 }
139