contextlistener.java

jsp 应用开发技术光盘 是《jsp应用开发技术》这本书的源代码

package listeners;

import database.BookDBAO;
import javax.servlet.*;
import util.Counter;


public final class ContextListener implements ServletContextListener {
    private ServletContext context = null;

    public void contextInitialized(ServletContextEvent event) {
        context = event.getServletContext();

        /*
         * 实例化BookDBAO，并将BookDBAO对象放入Servlet上下文
         */
        try {
            BookDBAO bookDB = new BookDBAO();
            context.setAttribute("bookDB", bookDB);
        } catch (Exception ex) {
            System.out.println("Couldn't create bookstore database bean: " +
                ex.getMessage());
        }

        Counter counter = new Counter();
        context.setAttribute("hitCounter", counter);
        counter = new Counter();
        context.setAttribute("orderCounter", counter);
    }

    public void contextDestroyed(ServletContextEvent event) {
        context = event.getServletContext();
        /*
         * 程序运行结束，从Servlet上下文中删除BookDBAO对象，关闭数据库连接
         */
        BookDBAO bookDB = (BookDBAO) context.getAttribute("bookDB");

        if (bookDB != null) {
            bookDB.remove();
        }

        context.removeAttribute("bookDB");
        context.removeAttribute("hitCounter");
        context.removeAttribute("orderCounter");
    }
}