/* * $Id: MemoryDatabasePlugIn.java 54929 2004-10-16 16:38:42Z germuska $  * * Copyright 2000-2004 Apache Software Foundation * * Licensed 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.examples.mailreader.memory;import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;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.examples.mailreader.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> * * @version $Rev: 54929 $ $Date: 2004-10-16 09:38:42 -0700 (Sat, 16 Oct 2004) $ */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);    }    // --------------------------------------------------------- Public Methods    // ------------------------------------------------------ Protected Methods    // -------------------------------------------------------- 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());    }}