原理：
下面一个简单的demo：在访问购买servlet时创建一个session，key为name
在访问购买servlet时取出值来进行购买
/**
* 购买servlet
*/
@WebServlet("/sessionDemo1")
public class sessionDemo1 extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session=request.getSession();
session.setAttribute("name", "洗衣机");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
/**
* 结账servlet
*/
@WebServlet("/sessionDemo2")
public class sessionDemo2 extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setCharacterEncoding("UTF_8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out=response.getWriter();
Object value=request.getSession().getAttribute("name");
out.write(value.toString());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
session生命周期：
第一个getsession出现时创建，第二getssesion出现时取值
默认30分钟没活动就会才摧毁
也可以设失效时间在web.xml
------>十分钟失效
代码方式摧毁session
session.invalidate();
场景————————》电商网站，选择好的商品关闭浏览器就丢失，所以这里需要分析下session的原理
每个浏览器有一个session，两个连接的关键点在于用JSESSIONID来寻找对应的session
关闭浏览器，再重新访问，虽然session还存在，因为JSESSIONID没有传入进来所以不知道寻找哪个session
通过如下代码给浏览器回写给浏览器JSESSIONID：
HttpSession session=request.getSession();
String sessionId=session.getId();
Cookie cookie=new Cookie("JSESSIONID", sessionId);
cookie.setMaxAge(30*60);
cookie.setPath("/day06");
response.addCookie(cookie);
浏览器可以控制cookie被禁，因为session基于cookies，这样session也就不能正常进行
getsession这个方法逻辑是这样的------》先判断是否以cookies回写JSESSION，在判断是否以URL形式带来JSESSION，都没有创建新的session
如果这样写----》getsession（false）只读取，不创建
所以解决cookie被禁的方法是重写url
response.encodeURL(URL)----->自动给这个url加上JSESSION
特例：在IE8版本的浏览器里，开新浏览器不创建新的session，用的是同一个
下面给一个用户登录时，密码正确就给用户一个登录的session标记，退出就销毁session，下面是demo
效果：
先登录----》aa aa---->登录成功------》注销----》弹回登录页面
-----》
----
---》
-----》
LoginServlet.java
/**
* 登录
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setCharacterEncoding("UTF_8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out=response.getWriter();
String username=request.getParameter("username");
String password=request.getParameter("password");
List<User> lists=DB.getAll();
for(User list:lists){
if(list.getUsername().equals(username)){
if(list.getPassword().equals(password)){
request.getSession().setAttribute("user", list);// 登录成功往session里存入登录标记
response.sendRedirect("/day06/index.jsp");//重定向到首页
return;
}
}
}
out.write("用户名或者密码不对");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
@SuppressWarnings("unchecked")
class DB{//模拟数据库
@SuppressWarnings("rawtypes")
public static List list=new ArrayList();
static{
list.add(new User("aa","aa"));
list.add(new User("bb","bb"));
list.add(new User("cc","cc"));
}
@SuppressWarnings("rawtypes")
public static List getAll(){
return list;
}
}
login.html
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> <form action="/day06/LoginServlet" method="post "> 用户名：<input type="text" name="username" /> 密码：<input type="password" name="password" /> <input type="submit" value="提交"> </form> </body> </html>
user.java(用户实体)
/**
*
*/
package session;
/**
* @author: snowing
* @date : 2017年4月9日
*
*/
public class User {
private String username;
private String password;
/**
* @param string
* @param string2
*/
public String getUsername() {
return username;
}
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(String username, String password) {
super();
this.username = username;
this.password = password;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
index.jsp(登录成功页面)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Insert title here</title>
</head>
<body>
success！！${user.username} <a href="/day06/LoginoutServlet">注销登录</a>
</body>
</html>
LoginoutServlet.java
/**
* 登出
*/
@WebServlet("/LoginoutServlet")
public class LoginoutServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session=request.getSession(false);
if(session==null){
response.sendRedirect("/day06/login.html");
return;
}
session.removeAttribute("user");
response.sendRedirect("/day06/login.html");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}