Source code: org/objectstyle/cayenne/conf/WebApplicationListener.java
1 /* ====================================================================
2 *
3 * The ObjectStyle Group Software License, Version 1.0
4 *
5 * Copyright (c) 2002-2003 The ObjectStyle Group
6 * and individual authors of the software. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
18 * distribution.
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20 * 3. The end-user documentation included with the redistribution, if
21 * any, must include the following acknowlegement:
22 * "This product includes software developed by the
23 * ObjectStyle Group (http://objectstyle.org/)."
24 * Alternately, this acknowlegement may appear in the software itself,
25 * if and wherever such third-party acknowlegements normally appear.
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27 * 4. The names "ObjectStyle Group" and "Cayenne"
28 * must not be used to endorse or promote products derived
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30 * permission, please contact andrus@objectstyle.org.
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32 * 5. Products derived from this software may not be called "ObjectStyle"
33 * nor may "ObjectStyle" appear in their names without prior written
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50 * This software consists of voluntary contributions made by many
51 * individuals on behalf of the ObjectStyle Group. For more
52 * information on the ObjectStyle Group, please see
53 * <http://objectstyle.org/>.
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55 */
56
57 package org.objectstyle.cayenne.conf;
58
59 import javax.servlet.ServletContext;
60 import javax.servlet.ServletContextEvent;
61 import javax.servlet.ServletContextListener;
62 import javax.servlet.http.HttpSessionEvent;
63 import javax.servlet.http.HttpSessionListener;
64
65 /**
66 * WebApplicationListener utilizes Servlet specification 2.3 features to react on
67 * webapplication container events inializing Cayenne.
68 *
69 * <p>It performs the following tasks:
70 * <ul>
71 * <li>Loads Cayenne configuration when the application is started within container.</li>
72 * <li>Assigns new DataContext to every new session created within the application.</li>
73 * </ul>
74 * </p>
75 *
76 * <p>CayenneWebappListener must be configured in <code>web.xml</code> deployment
77 * descriptor as a listener of context and session events:</p>
78 *<pre><listener>
79 <listener-class>org.objectstyle.cayenne.conf.WebApplicationListener</listener-class>
80 </listener></pre>
81 *
82 * <p>Note that to set WebApplicationListener as a listener of web application events,
83 * you must use servlet containers
84 * compatible with Servlet Specification 2.3 (such as Tomcat 4.0). Listeners were only added
85 * to servlet specification in 2.3. If you are using an older container, you will need
86 * to configure Cayenne in your code.</p>
87 *
88 * @author Andrei Adamchik
89 */
90 public class WebApplicationListener
91 implements HttpSessionListener, ServletContextListener {
92
93 public WebApplicationListener() {
94 }
95
96 /** Establishes a Cayenne shared Configuration object that can later be obtained by calling
97 * <code>Configuration.getSharedConfiguration()</code>.
98 * This method is a part of ServletContextListener interface and is called
99 * on application startup. */
100 public void contextInitialized(ServletContextEvent sce) {
101 setConfiguration(newConfiguration(sce.getServletContext()));
102 }
103
104 /** Currently does nothing. <i>In the future it should close down
105 * any database connections if they wheren't obtained via JNDI.</i>
106 * This method is a part of ServletContextListener interface and is called
107 * on application shutdown. */
108 public void contextDestroyed(ServletContextEvent sce) {
109 }
110
111 /** Creates and assigns a new data context based on default domain
112 * to the session object associated with this event. This method
113 * is a part of HttpSessionListener interface and is called every time
114 * when a new session is created. */
115 public void sessionCreated(HttpSessionEvent se) {
116 se.getSession().setAttribute(
117 BasicServletConfiguration.DATA_CONTEXT_KEY,
118 getConfiguration().getDomain().createDataContext());
119 }
120
121 /** Does nothing. This method
122 * is a part of HttpSessionListener interface and is called every time
123 * when a session is destroyed. */
124 public void sessionDestroyed(HttpSessionEvent se) {
125 }
126
127 /** Return an instance of Configuration that will be initialized as the shared configuration.
128 * Provides an extension point for the developer to provide their own custom configuration.
129 */
130 protected Configuration newConfiguration(ServletContext sc) {
131 return new BasicServletConfiguration(sc);
132 }
133
134 /** Initializes the configuration. */
135 protected void setConfiguration(Configuration configuration) {
136 Configuration.initializeSharedConfiguration(configuration);
137 }
138
139 /** Returns the current configuration. */
140 protected Configuration getConfiguration() {
141 return Configuration.getSharedConfiguration();
142 }
143 }