jsp-application应用

application有两种应用，1是当作map，代码如下

1 <body>
2 <%!
3     int i=1;
4 %>
5 <%
6 application.setAttribute("count",String.valueOf(i++));
7 %>
8 <%=application.getAttribute("count") %>
9 </body>

利用setAttribute和getAttribute。

2是读取web.xml配置信息，代码如下：首先web.xml代码：

 1     <!--配置欢迎页 -->
 2     <welcome-file-list>
 3         <welcome-file>index.jsp</welcome-file>
 4     </welcome-file-list>
 5     <!-- 驱动 -->
 6     <context-param>
 7         <param-name>driver</param-name>
 8         <param-value>com.mysql.jdbc.Driver</param-value>
 9     </context-param>
10     <context-param>
11         <!-- url -->
12         <param-name>url</param-name>
13         <param-value>jdbc:mysql://localhost:3306/house</param-value>
14     </context-param>
15     <!-- 连接用户 -->
16     <context-param>
17         <param-name>user</param-name>
18         <param-value>root</param-value>
19     </context-param>
20     <!-- 连接密码 -->
21     <context-param>
22         <param-name>pwd</param-name>
23         <param-value>123456</param-value>
24     </context-param>

然后jsp代码：

<%@page import="java.sql.ResultSet"%>
<%@page import="com.mysql.jdbc.Statement"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="com.mysql.jdbc.Connection"%>
<%@ page language="java" contentType="text/html; charset=gbk"
    pageEncoding="gbk"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>Insert title here</title>
</head>
<body>
    <%
        String driver = application.getInitParameter("driver");
        String url = application.getInitParameter("url");
        String user = application.getInitParameter("user");
        String pwd = application.getInitParameter("pwd");
        //加载驱动
        Class.forName(driver);
        //建立连接
        Connection conn = (Connection) DriverManager.getConnection(url, user, pwd);
        //创建Statement
        Statement stm = (Statement) conn.createStatement();
        //执行查询
        ResultSet rs = stm.executeQuery("select username,pwd from user");
    %>
    <table border="1" width="300">
        <%
            //遍历结果
            while (rs.next()) {
        %>
        <tr>
            <td><%=rs.getString(1)%></td>
            <td><%=rs.getString(2)%></td>
        </tr>
        <%
            }
        %>
    </table>
</body>
</html>