JAVA WEB:application与session对象使用范例与差异深度分析

浏览数：24 / 时间：2015年06月11日

1.本文分析一下request对象中getParameter方法及getAttribute的差异及使用场景。

这个关系到servlet的生命周期

很简单的一个例子，上代码

页面1 ：request1.jsp

 1 <%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
 2 <%
 3 String path = request.getContextPath();
 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 5 %>
 6 <html>
 7 <head>
 8 
 9 <title>1</title>
10 </head>
11 <body>
12         <form    action="request2.jsp">
13                     
14             username:<input type="text" name="username">
15 
16             <input type="submit" value="submit">                    
17             </form>
18 </body>
19 </html>

这个JSP 从text框获取一个文本值（用户名）

然后在request2.jsp中调用getParameter方法获取改对象

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>2</title>
 8 </head>
 9 <body>
10 
11 <% 
12     String username = request.getParameter("username");
13 
14 %>
15 
16         username: <%=username %>
17         
18         <% request.setAttribute("username", username);%>
19         
20         
21         <jsp:forward="request3.jsp"></jsp:forward>
22 </body>
23 </html>

显示成功。

我们在request2.jsp中将username再set到request中传递给第三个页面request3.jsp

 1 <%@ page language="java" contentType="text/html; charset=ISO-8859-1"
 2     pageEncoding="ISO-8859-1"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 7 <title>3</title>
 8 </head>
 9 <body>
10     <% String username = (String)request.getAttribute("username");%>
11     
12     username:<%=username %>
13 </body>
14 </html>

然后在request3.JSP中用getAtterbute方法获取该对象

但是二者有什么区别呢，我们将request2.jsp修改一下即可看出差别

修改后的request2.JSP

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>2</title>
 8 </head>
 9 <body>
10 
11 <% 
12     String username = request.getParameter("username");
13 
14 %>
15 
16         username: <%=username %>
17         
18         <% request.setAttribute("username", username);%>
19         
20         
21         <a href="request3.jsp">request3.jsp</a>
22 </body>
23 </html>