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


1 /* ====================================================================
2  *
3  * The ObjectStyle Group Software License, version 1.1
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7  * of the software. All rights reserved.
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26  * if and wherever such third-party acknowlegements normally appear.
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56 package org.objectstyle.cayenne.conf;
57
58 import javax.servlet.ServletContext JavaDoc;
59 import javax.servlet.http.HttpSession JavaDoc;
60
61 import org.apache.log4j.Logger;
62 import org.objectstyle.cayenne.access.DataContext;
63 import org.objectstyle.cayenne.util.ResourceLocator;
64 import org.objectstyle.cayenne.util.WebApplicationResourceLocator;
65
66 /**
67  * Configuration class that uses ServletContext to locate resources. This class is
68  * intended for use in J2EE servlet containers. It is compatible with containers following
69  * servlet specification version 2.2 and newer (e.g. Tomcat can be used starting from
70  * version 3).
71  * <p>
72  * ServletConfiguration resolves configuration file locations relative to the web
73  * application "WEB-INF" directory, and does not require them to be in the CLASSPATH
74  * (though CLASSPATH locations such as "/WEB-INF/classes" and "/WEB-INF/lib/some.jar" are
75  * supported as well). By default search for cayenne.xml is done in /WEB-INF/ folder. To
76  * specify an arbitrary context path in the web application (e.g. "/WEB-INF/cayenne"), use
77  * <code>cayenne.configuration.path</code> context parameters in <code>web.xml</code>.
78  * </p>
79  *
80  * @author Andrei Adamchik
81  * @author Scott Finnerty
82  * @since 1.2
83  */
84 public class ServletUtil {
85
86     private static Logger logObj = Logger.getLogger(ServletUtil.class);
87
88     /**
89      * A name of the web application initialization parameter used to specify extra paths
90      * where Cayenne XML files might be located. E.g. "/WEB-INF/cayenne".
91      */
92     public static final String JavaDoc CONFIGURATION_PATH_KEY = "cayenne.configuration.path";
93
94     /**
95      * Used by BasicServletConfiguration as a session attribute for DataContext.
96      */
97     public static final String JavaDoc DATA_CONTEXT_KEY = "cayenne.datacontext";
98
99     /**
100      * Creates a new ServletConfiguration and sets is as a Configuration signleton.
101      */
102     public synchronized static Configuration initializeSharedConfiguration(
103             ServletContext JavaDoc context) {
104
105         // check if this web application is already configured
106
107         // don't use static getter, since it will do initialization on demand!!!
108 Configuration oldConfig = Configuration.sharedConfiguration;
109         if (oldConfig instanceof DefaultConfiguration) {
110
111             ResourceLocator locator = ((DefaultConfiguration) oldConfig)
112                     .getResourceLocator();
113
114             if (locator instanceof WebApplicationResourceLocator) {
115                 if (((WebApplicationResourceLocator) locator).getServletContext() == context) {
116                     logObj
117                             .info("Configuration is already initialized with this context, reusing.");
118                     return oldConfig;
119                 }
120             }
121         }
122
123         // create new shared configuration
124 DefaultConfiguration conf = new DefaultConfiguration(
125                 Configuration.DEFAULT_DOMAIN_FILE,
126                 createLocator(context));
127         Configuration.initializeSharedConfiguration(conf);
128
129         return conf;
130     }
131
132     /**
133      * A helper method to create default ResourceLocator.
134      */
135     protected static ResourceLocator createLocator(ServletContext JavaDoc context) {
136         WebApplicationResourceLocator locator = new WebApplicationResourceLocator();
137         locator.setSkipAbsolutePath(true);
138         locator.setSkipClasspath(false);
139         locator.setSkipCurrentDirectory(true);
140         locator.setSkipHomeDirectory(true);
141
142         locator.setServletContext(context);
143         String JavaDoc configurationPath = context.getInitParameter(CONFIGURATION_PATH_KEY);
144         if (configurationPath != null && configurationPath.trim().length() > 0) {
145             locator.addFilesystemPath(configurationPath.trim());
146         }
147
148         return locator;
149     }
150
151     /**
152      * Returns default Cayenne DataContext associated with the HttpSession, creating it on
153      * the fly and storing in the session if needed.
154      */
155     public static DataContext getSessionContext(HttpSession JavaDoc session) {
156         synchronized (session) {
157             DataContext ctxt = (DataContext) session.getAttribute(DATA_CONTEXT_KEY);
158
159             if (ctxt == null) {
160                 ctxt = DataContext.createDataContext();
161                 session.setAttribute(ServletUtil.DATA_CONTEXT_KEY, ctxt);
162             }
163
164             return ctxt;
165         }
166     }
167 }
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