Web开发基础_Servlet学习_0028_状态管理

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/Coder_Boy_/article/details/82723252

Session

案例演示思路：

案例演示：

工程案例目录结构

 web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <display-name>Jsp05</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
  	<servlet-name>create</servlet-name>
  	<servlet-class>web.CreateServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>create</servlet-name>
  	<url-pattern>/create</url-pattern>
  </servlet-mapping>
  
  <servlet>
  	<servlet-name>view</servlet-name>
  	<servlet-class>web.ViewServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>view</servlet-name>
  	<url-pattern>/view</url-pattern>
  </servlet-mapping>
  
  <servlet>
  	<servlet-name>modify</servlet-name>
  	<servlet-class>web.ModifyServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>modify</servlet-name>
  	<url-pattern>/modify</url-pattern>
  </servlet-mapping>
  
  <!-- 
  	配置session超时时间（分钟）
  	当用户的空闲（不操作）时间超出该时间时，
  	服务器将销毁此session。
   -->
  <session-config>
  	<session-timeout>1</session-timeout>
  </session-config>
</web-app>

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.study</groupId>
  <artifactId>Jsp05</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  
   <dependencies>
  	<dependency>
  		<groupId>javaee</groupId>
  		<artifactId>javaee-api</artifactId>
  		<version>5</version>
  	</dependency>
  </dependencies>
</project>

CreateServlet.java

package web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class CreateServlet extends HttpServlet{

	@Override
	protected void service(HttpServletRequest req,
			HttpServletResponse res) throws ServletException, IOException {
			
			//首次访问此项目时，服务器会给这个
			//浏览器创建一个session，并存入request
			HttpSession session = req.getSession();
			//session中可以存储任何类型的数据
			session.setAttribute("user", "caocao");
			
			//session中可以直接存储中文
			session.setAttribute("city", "北京");
	}
	
	

}

ViewServlet.java

package web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ViewServlet extends HttpServlet{

	@Override
	protected void service(HttpServletRequest req,
			HttpServletResponse res) throws ServletException, IOException {
			
			HttpSession session = req.getSession();
			String user = (String)session.getAttribute("user");
			System.out.println(user);
			
			String city = (String)session.getAttribute("city");
			System.out.println(city);
			
			req.getRequestDispatcher("WEB-INF/view.jsp").forward(req, res);
	}
	
	

}

ModifyServlet.java

package web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ModifyServlet extends HttpServlet{

	@Override
	protected void service(HttpServletRequest req,
			HttpServletResponse res) throws ServletException, IOException {
			HttpSession session = req.getSession();
			
			//修改数据（覆盖）
			session.setAttribute("user", "LiuBei");
		 	
			//删除数据
			session.removeAttribute("city");
			
			
	}

	
}

view.jsp

<%@page pageEncoding="utf-8"%>
<!doctype html>
<html>
	<head>
		<meta charset="utf-8">
		<title>session</title>
	</head>
	<body>
		<!-- 
			EL的取值范围：{处理字符串null-。不显示}
			page->request->session->application
		 -->
		 <p>${user }</p>
		 <p>${city }</p>
	</body>
</html>

将Jsp05工程部署到Tomcat上，运行Tomcat启动案例工程，

浏览器录入http://localhost:8080/Jsp05/create 创建一个session

浏览器再录入http://localhost:8080/Jsp05/view 显示这个一个session 

页面显示：

 浏览器录入http://localhost:8080/Jsp05/modify 显示这个一个session

浏览器再录入http://localhost:8080/Jsp05/view 显示这个一个session

页面显示：

 

  <!-- 
      配置session超时时间（分钟）
      当用户的空闲（不操作）时间超出该时间时，
      服务器将销毁此session。
   -->
  <session-config>
      <session-timeout>1</session-timeout>
  </session-config>

对应session超时设置：

我们不操作浏览器等待1分钟后再次 请求 http://localhost:8080/Jsp05/view 

浏览器页面显示及后台输出：

A.

B.