Servlet------>session

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;
	}
}

<!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);
	}

}

posted on 2017-04-07 14:46 Snowing杨雪莹阅读(235) 评论(4) 收藏举报