摘要：
当web应用在web容器中运行时，web应用内部会不断地发生各种事件：如web应用被启动东，web应用被停止，用户session开始，用户session结束，用户请求到达等等……,这些web事情对开发者是透明的，通过监听器我们可以知道web容器里面发生的任何事情。
ServletContextListener
常用的监听器有
ServletContextListener：用来监听web应用的启动和关闭
contextInitialized(ServletContextEvent arg0) 当web应用被启动的时候执行
contextDestroyed(ServletContextEvent arg0)当web应用被启动关闭时执行
监听的配置有两种方式：
第一种是web注解的方式
第二种是在xml文件里面配置
1 package com.huayu.listener;
2
3 import javax.servlet.ServletContextEvent;
4 import javax.servlet.ServletContextListener;
5
6 public class Listener1 implements ServletContextListener{
7
8 @Override
9 public void contextDestroyed(ServletContextEvent arg0) {
10 // TODO Auto-generated method stub
11 System.out.println("=========应用关闭============");
12 }
13
14 @Override
15 public void contextInitialized(ServletContextEvent arg0) {
16 // TODO Auto-generated method stub
17 System.out.println("===应用启动=========");
18 }
19
20 }
web.xml
1 <listener> 2 <listener-class>com.huayu.listener.Listener1</listener-class> 3 </listener>
下面演示：
写一个ServletContextListener监听器，当web应用启动是链接orcl数据库,在jsp页面中将emp表里面的数据以表格的形式打印出来，当web应用关闭时断开与orcl数据库的链接
1 package com.huayu.listener;
2
3 import java.sql.Connection;
4 import java.sql.DriverManager;
5 import java.sql.PreparedStatement;
6 import java.sql.SQLException;
7
8 import javax.servlet.ServletContext;
9 import javax.servlet.ServletContextEvent;
10 import javax.servlet.ServletContextListener;
11
12 public class Listener1 implements ServletContextListener{
13
14 @Override
15 public void contextDestroyed(ServletContextEvent arg0) {
16
17 ServletContext application=arg0.getServletContext();
18 Connection conn=(Connection) application.getAttribute("connoracle");
19 if(conn!=null){
20
21 try {
22 conn.close();
23 } catch (SQLException e) {
24 // TODO Auto-generated catch block
25 e.printStackTrace();
26 }
27 }
28
29 }
30
31 @Override
32 public void contextInitialized(ServletContextEvent arg0) {
33 // TODO Auto-generated method stub
34 String driver="oracle.jdbc.driver.OracleDriver";
35 String url="jdbc:oracle:thin:@localhost:1521:orcl";
36 String user="scott";
37 String pass="ztoracle";
38
39 ServletContext application=arg0.getServletContext();
40
41 try {
42 Class.forName(driver);
43 Connection conn=DriverManager.getConnection(url, user, pass);
44 application.setAttribute("connoracle", conn);
45
46 } catch (Exception e) {
47 throw new RuntimeException();
48
49
50 }
51
52 }
53
54 }
1 <%@page import="java.sql.ResultSetMetaData"%>
2 <%@page import="java.sql.ResultSet"%>
3 <%@page import="java.sql.PreparedStatement"%>
4 <%@page import="java.sql.Connection"%>
5 <%@ page language="java" import="java.util.*" pageEncoding="GBK" contentType="text/html; charset=GBK"%>
6 <%
7 String path = request.getContextPath();
8 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
9 %>
10
11 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
12 <html>
13 <head>
14 <base href="<%=basePath%>">
15
16 <title>My JSP ‘index.jsp‘ starting page</title>
17 <meta http-equiv="pragma" content="no-cache">
18 <meta http-equiv="cache-control" content="no-cache">
19 <meta http-equiv="expires" content="0">
20 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
21 <meta http-equiv="description" content="This is my page">
22 <!--
23 <link rel="stylesheet" type="text/css" href="styles.css">
24 -->
25 </head>
26
27 <body>
28 <%
29 Connection conn=(Connection)application.getAttribute("connoracle");
30 PreparedStatement ps=conn.prepareStatement("select * from emp");
31 ResultSet rs=ps.executeQuery();
32 ResultSetMetaData rsm=rs.getMetaData();
33 int count=rsm.getColumnCount();
34 %>
35 <table border="1">
36 <%
37 while(rs.next()){
38 %>
39 <tr>
40 <%
41 for(int i=0;i<count;i++){
42
43 %>
44 <td>
45 <%
46 rs.getString(i+1);
47 %>
48
49
50 </td>
51 <% } %>
52 </tr>
53 <%} %>
54 </table>
55
56 </body>
57 </html>
时间： 2024-12-18 00:14:09