userdatabaseplugin.java

一个很好的使用struts技术的地址簿的例子,很值得

package addressbook;

import java.io.BufferedInputStream;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.IOException;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.io.PrintStream;
import java.io.FileOutputStream;
import java.net.MalformedURLException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.MissingResourceException;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.commons.digester.Digester;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.struts.util.MessageResources;
import addressbook.model.UserBean;
import org.apache.struts.action.PlugIn;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.action.ActionServlet;

/**
 * <strong>UserDatabasePlugIn</strong> is used to read username/password information
 * to an XML file.
 *<p>
 * The Addressbook sample application uses this file for demonstration purposes by reading the database
 * file from <code> /WEB-INF/userdatabase.xml </code>. In a production
 * application you would not want to store username/password information in a clear text file. More
 * likely, you would have this information contained within a database for a lookup at logon time.
 */
public final class UserDatabasePlugIn implements PlugIn{

    private Hashtable database = null;
    private Log log = LogFactory.getLog(this.getClass().getName());

    private String pathname;
    public String getPathname() {
        return pathname;
    }
    public void setPathname(String pathname) {
        this.pathname = pathname;
    }

    public void destroy() {
         database = null;
    }

   public void addUser(UserBean user){
        database.put(user.getUserName(),user);
    }
   public void init(ActionServlet servlet, ModuleConfig config)
    throws ServletException{
	try {
	/* Try and load the database.xml file. If we have loaded,
	 * store the contents into our context so that we can use it
	 * to compare against for user logons.
	 */
	    load(servlet);
	    servlet.getServletContext().setAttribute(Constants.DATABASE_KEY,
					     database);
	} catch (Exception e) {
	    log.debug("Database load exception", e);
	    throw new UnavailableException
		("Cannot load database from '" + pathname + "'"+e.getMessage());
	}

    }


    /**
     * Load the current database.xml file. Using the <code>Digester<code>
     * @see org.apache.commons.digester.Digester
     */


    private synchronized void load(ActionServlet servlet) throws Exception {
	database = new Hashtable();
	log.debug("Loading database from '" + pathname + "'");
   	InputStream is = servlet.getServletContext().getResourceAsStream(pathname);
   	if (is == null) {
       log.debug("No such resource available - loading empty database");
       return;
   	}
	BufferedInputStream bis = new BufferedInputStream(is);
	Digester digester = new Digester();
	digester.push(this);
	digester.setDebug(2);
	digester.setValidating(false);
	digester.addObjectCreate("database/user", "addressbook.model.UserBean");
	digester.addSetProperties("database/user");
	digester.addSetNext("database/user", "addUser");

	digester.parse(bis);
	bis.close();

    }
}