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Java > Open Source Codes > org > objectstyle > cayenne > conf > WebApplicationListener


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2  *
3  * The ObjectStyle Group Software License, version 1.1
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56
57 package org.objectstyle.cayenne.conf;
58
59 import javax.servlet.ServletContext JavaDoc;
60 import javax.servlet.ServletContextEvent JavaDoc;
61 import javax.servlet.ServletContextListener JavaDoc;
62 import javax.servlet.http.HttpSessionEvent JavaDoc;
63 import javax.servlet.http.HttpSessionListener JavaDoc;
64
65 /**
66  * WebApplicationListener utilizes Servlet specification 2.3 features to react on
67  * webapplication container events inializing Cayenne.
68  * <p>
69  * It performs the following tasks:
70  * <ul>
71  * <li>Loads Cayenne configuration when the application is started within container.
72  * </li>
73  * <li>Assigns new DataContext to every new session created within the application.</li>
74  * </ul>
75  * </p>
76  * <p>
77  * CayenneWebappListener must be configured in <code>web.xml</code> deployment
78  * descriptor as a listener of context and session events:
79  * </p>
80  *
81  * <pre>
82  * &lt;listener&gt;
83  * &lt;listener-class&gt;org.objectstyle.cayenne.conf.WebApplicationListener&lt;/listener-class&gt;
84  * &lt;/listener&gt;
85  * </pre>
86  *
87  * <p>
88  * Note that to set WebApplicationListener as a listener of web application events, you
89  * must use servlet containers compatible with Servlet Specification 2.3 (such as Tomcat
90  * 4.0). Listeners were only added to servlet specification in 2.3. If you are using an
91  * older container, you will need to configure Cayenne in your code.
92  * </p>
93  *
94  * @author Andrei Adamchik
95  */
96 public class WebApplicationListener implements HttpSessionListener JavaDoc,
97         ServletContextListener JavaDoc {
98
99     /**
100      * Establishes a Cayenne shared Configuration object that can later be obtained by
101      * calling <code>Configuration.getSharedConfiguration()</code>. This method is a
102      * part of ServletContextListener interface and is called on application startup.
103      */
104     public void contextInitialized(ServletContextEvent JavaDoc sce) {
105         ServletUtil.initializeSharedConfiguration(sce.getServletContext());
106     }
107
108     /**
109      * Currently does nothing. <i>In the future it should close down any database
110      * connections if they wheren't obtained via JNDI. </i> This method is a part of
111      * ServletContextListener interface and is called on application shutdown.
112      */
113     public void contextDestroyed(ServletContextEvent JavaDoc sce) {
114     }
115
116     /**
117      * Creates and assigns a new data context based on default domain to the session
118      * object associated with this event. This method is a part of HttpSessionListener
119      * interface and is called every time when a new session is created.
120      */
121     public void sessionCreated(HttpSessionEvent JavaDoc se) {
122         se.getSession().setAttribute(
123                 ServletUtil.DATA_CONTEXT_KEY,
124                 getConfiguration().getDomain().createDataContext());
125     }
126
127     /**
128      * Does nothing. This method is a part of HttpSessionListener interface and is called
129      * every time when a session is destroyed.
130      */
131     public void sessionDestroyed(HttpSessionEvent JavaDoc se) {
132     }
133
134     /**
135      * Returns an instance of Configuration that will be initialized as the shared
136      * configuration. Provides an extension point for the developer to provide their own
137      * custom configuration.
138      *
139      * @deprecated since 1.2
140      */
141     protected Configuration newConfiguration(ServletContext JavaDoc sc) {
142         return new BasicServletConfiguration(sc);
143     }
144
145     /**
146      * Initializes the configuration.
147      */
148     protected void setConfiguration(Configuration configuration) {
149         Configuration.initializeSharedConfiguration(configuration);
150     }
151
152     /** Returns the current configuration. */
153     protected Configuration getConfiguration() {
154         return Configuration.getSharedConfiguration();
155     }
156 }
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