/*
* $Id: MemoryDatabasePlugIn.java 471754 2006-11-06 14:55:09Z 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 org.apache.struts.webapp.example.memory;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.ArrayList;
import javax.servlet.ServletException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.PlugIn;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.util.LabelValueBean;
import org.apache.struts.webapp.example.Constants;
/**
* <p><strong>MemoryDatabasePlugIn</strong> 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><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>
*
* @author Craig R. McClanahan
* @version $Rev: 471754 $ $Date: 2006-11-06 15:55:09 +0100 (Lun, 06 nov 2006) $
*/
public final class MemoryDatabasePlugIn implements PlugIn {
// ----------------------------------------------------- Instance Variables
/**
* The {@link MemoryUserDatabase} object we construct and make available.
*/
private MemoryUserDatabase database = null;
/**
* Logging output for this plug in instance.
*/
private Log log = LogFactory.getLog(this.getClass());
/**
* The {@link ActionServlet} owning this application.
*/
private ActionServlet servlet = null;
// ------------------------------------------------------------- Properties
/**
* The web application resource path of our persistent database
* storage file.
*/
private String pathname = "/WEB-INF/database.xml";
public String getPathname() {
return (this.pathname);
}
public void setPathname(String pathname) {
this.pathname = pathname;
}
// --------------------------------------------------------- PlugIn Methods
/**
* Gracefully shut down this database, releasing any resources
* that were allocated at initialization.
*/
public void destroy() {
log.info("Finalizing memory database plug in");
if (database != null) {
try {
database.close();
} catch (Exception e) {
log.error("Closing memory database", e);
}
}
servlet.getServletContext().removeAttribute(Constants.DATABASE_KEY);
database = null;
servlet = null;
database = null;
}
/**
* Initialize and load our initial database from persistent storage.
*
* @param servlet The ActionServlet for this web application
* @param config The ApplicationConfig for our owning module
*
* @exception ServletException if we cannot configure ourselves correctly
*/
public void init(ActionServlet servlet, ModuleConfig config)
throws ServletException {
log.info("Initializing memory database plug in from '" +
pathname + "'");
// Remember our associated configuration and servlet
this.servlet = servlet;
// 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 ServletException("Cannot load database from '" +
pathname + "'", e);
}
// Make the initialized database available
servlet.getServletContext().setAttribute(Constants.DATABASE_KEY,
database);
// Setup and cache other required data
setupCache(servlet, config);
}
// --------------------------------------------------------- Public Methods
// ------------------------------------------------------ Protected Methods
/**
* <p>Cache commonly required data as servlet context attributes.</p>
*
* @param servlet The <code>ActionServlet</code> instance running
* this webapp
* @param config The <code>ModuleConfig</code> for this application module
*/
protected void setupCache(ActionServlet servlet, ModuleConfig config) {
// Set up list of server types under "serverTypes"
ArrayList serverTypes = new ArrayList();
serverTypes.add(new LabelValueBean("IMAP Protocol", "imap"));
serverTypes.add(new LabelValueBean("POP3 Protocol", "pop3"));
servlet.getServletContext().setAttribute("serverTypes", serverTypes);
}
// -------------------------------------------------------- Private Methods
/**
* Calculate and return an absolute pathname to the XML file to contain
* our persistent storage information.
*
* @exception Exception if an input/output error occurs
*/
private String calculatePath() throws Exception {
// Can we access the database via file I/O?
String path = servlet.getServletContext().getRealPath(pathname);
if (path != null) {
return (path);
}
// Does a copy of this file already exist in our temporary directory
File dir = (File)
servlet.getServletContext().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 =
servlet.getServletContext().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());
}
}