/*
* $Id: ApplicationListener.java 471756 2006-11-06 15:01:43Z husted $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package mailreader2;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.apps.mailreader.dao.impl.memory.MemoryUserDatabase;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.io.*;
/**
* <p><code>ServletContextListener</code> that initializes and finalizes the
* persistent storage of User and Subscription information for the Struts
* Demonstration Application, using an in-memory database backed by an XML
* file.</p>
* <p/>
* <p><strong>IMPLEMENTATION WARNING</strong> - If this web application is run
* from a WAR file, or in another environment where reading and writing of the
* web application resource is impossible, the initial contents will be copied
* to a file in the web application temporary directory provided by the
* container. This is for demonstration purposes only - you should
* <strong>NOT</strong> assume that files written here will survive a restart
* of your servlet container.</p>
* <p/>
* <p>This class was borrowed from the Shale Mailreader. Changes were:</p>
* <p/>
* <ul>
* <p/>
* <li>Path to database.xml (under classes here). </li>
* <p/>
* <li>Class to store protocol list (an array here). </li>
* <p/>
* </ul>
* <p>
* DEVELOPMENT NOTE - Another approach would be to instantiate the database via Spring.
* </p>
*/
public final class ApplicationListener implements ServletContextListener {
// ------------------------------------------------------ Manifest Constants
/**
* <p>Appication scope attribute key under which the in-memory version of
* our database is stored.</p>
*/
public static final String DATABASE_KEY = "database";
/**
* <p>Application scope attribute key under which the valid selection
* items for the protocol property is stored.</p>
*/
public static final String PROTOCOLS_KEY = "protocols";
// ------------------------------------------------------ Instance Variables
/**
* <p>The <code>ServletContext</code> for this web application.</p>
*/
private ServletContext context = null;
/**
* The {@link MemoryUserDatabase} object we construct and make available.
*/
private MemoryUserDatabase database = null;
/**
* <p>Logging output for this plug in instance.</p>
*/
private Log log = LogFactory.getLog(this.getClass());
// ------------------------------------------------------------- Properties
/**
* <p>The web application resource path of our persistent database storage
* file.</p>
*/
private String pathname = "/WEB-INF/database.xml";
/**
* <p>Return the application resource path to the database.</p>
*
* @return application resource path path to the database
*/
public String getPathname() {
return (this.pathname);
}
/**
* <p>Set the application resource path to the database.</p>
*
* @param pathname to the database
*/
public void setPathname(String pathname) {
this.pathname = pathname;
}
// ------------------------------------------ ServletContextListener Methods
/**
* <p>Gracefully shut down this database, releasing any resources that
* were allocated at initialization.</p>
*
* @param event ServletContextEvent to process
*/
public void contextDestroyed(ServletContextEvent event) {
log.info("Finalizing memory database plug in");
if (database != null) {
try {
database.close();
} catch (Exception e) {
log.error("Closing memory database", e);
}
}
context.removeAttribute(DATABASE_KEY);
context.removeAttribute(PROTOCOLS_KEY);
database = null;
context = null;
}
/**
* <p>Initialize and load our initial database from persistent
* storage.</p>
*
* @param event The context initialization event
*/
public void contextInitialized(ServletContextEvent event) {
log.info("Initializing memory database plug in from '" +
pathname + "'");
// Remember our associated ServletContext
this.context = event.getServletContext();
// Construct a new database and make it available
database = new MemoryUserDatabase();
try {
String path = calculatePath();
if (log.isDebugEnabled()) {
log.debug(" Loading database from '" + path + "'");
}
database.setPathname(path);
database.open();
} catch (Exception e) {
log.error("Opening memory database", e);
throw new IllegalStateException("Cannot load database from '" +
pathname + "': " + e);
}
context.setAttribute(DATABASE_KEY, database);
}
// -------------------------------------------------------- Private Methods
/**
* <p>Calculate and return an absolute pathname to the XML file to contain
* our persistent storage information.</p>
*
* @throws Exception if an input/output error occurs
*/
private String calculatePath() throws Exception {
// Can we access the database via file I/O?
String path = context.getRealPath(pathname);
if (path != null) {
return (path);
}
// Does a copy of this file already exist in our temporary directory
File dir = (File)
context.getAttribute("javax.servlet.context.tempdir");
File file = new File(dir, "struts-example-database.xml");
if (file.exists()) {
return (file.getAbsolutePath());
}
// Copy the static resource to a temporary file and return its path
InputStream is =
context.getResourceAsStream(pathname);
BufferedInputStream bis = new BufferedInputStream(is, 1024);
FileOutputStream os =
new FileOutputStream(file);
BufferedOutputStream bos = new BufferedOutputStream(os, 1024);
byte buffer[] = new byte[1024];
while (true) {
int n = bis.read(buffer);
if (n <= 0) {
break;
}
bos.write(buffer, 0, n);
}
bos.close();
bis.close();
return (file.getAbsolutePath());
}
}
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