initializelibrary.java

使用Servlet和JSP进行Web组件开发

/*
 * InitializeLibrary.java
 *
 * 
 */

package com.dvd.web;

import com.dvd.model.DVDItem;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletContextEvent;

/**
 *
 * @author  
 * @version
 *
 * Web application lifecycle listener.
 */

public class InitializeLibrary implements ServletContextListener {
    /**
     * ### Method from ServletContextListener ###
     * 
     * Called when a Web application is first ready to process requests
     * (i.e. on Web server startup and when a context is added or reloaded).
     * 
     * For example, here might be database connections established
     * and added to the servlet context attributes.
     */
    public void contextInitialized(ServletContextEvent evt) {
        List dvdList = new ArrayList();
        
        // Get filename paramater from the web.xml file
        ServletContext context = evt.getServletContext();
        String libraryFile = context.getInitParameter("library-file");
        
        InputStream is = null;
        BufferedReader reader = null;
        try {
            is = context.getResourceAsStream(libraryFile);
            reader = new BufferedReader(new InputStreamReader(is));
            String line;
            
            // Read every dvd entry in the file
            while ( (line = reader.readLine()) != null ) {
                String[] elements = line.split("\\|");
                
                // Extract the data fields for the record
                String title = elements[0];
                String year = elements[1];
                String genre = elements[2];
                
                // Add the new League item to the set
                DVDItem item = new DVDItem(title, year, genre);
                dvdList.add(item);
            }            
            context.setAttribute("dvdList", dvdList);            
            context.log("The DVD Library has been loaded from: " + libraryFile );            
        } catch (Exception e) {
            context.log("Exception occured while processing the DVD library file.", e);            
        } finally {
            if ( is != null ) {
                try { is.close(); } catch (Exception e) {}
            }
            if ( reader != null ) {
                try { reader.close(); } catch (Exception e) {}
            }
        }
    }

    /**
     * ### Method from ServletContextListener ###
     * 
     * Called when a Web application is about to be shut down
     * (i.e. on Web server shutdown or when a context is removed or reloaded).
     * Request handling will be stopped before this method is called.
     * 
     * For example, the database connections can be closed here.
     */
    public void contextDestroyed(ServletContextEvent evt) {
        // TODO add your code here e.g.:
        /*
                Connection con = (Connection) e.getServletContext().getAttribute("con");
                try { con.close(); } catch (SQLException ignored) { } // close connection
        */
    }
}