Session简介
Session是服务端技术，利用这个技术。利用这个技术，服务器在运行时可以为每一个用户的浏览器创建一个独享的session对象，由于Session为用户浏览器独享，所以用户在访问浏览器资源时，可以把各自的数据放在各自的session中，当用户再去访问服务器的其他web资源时，其他web资源再从用户各自的session中取出数据为用户服务。
创建或获取Session，并以Cookie的方式回写JSESSIONID。
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
//Session的另外一种获取方式，这种方式只获取不创建。比如查看购物车的操作，如果用户没有购物的话，没有必要创建一个Session。
// request.getSession(false);
String sessionid = session.getId();
Cookie cookie = new Cookie("JSESSIONID",sessionid);
cookie.setPath("/");
//设置cookie的保存时长为30分钟，因为Session一般就在服务器中保存30分钟，多了也没用。。。
cookie.setMaxAge(30*60);
response.addCookie(cookie);
session.setAttribute("name","洗衣机");
}
获取Session中的内容
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();
HttpSession session = request.getSession();
String product = (String) session.getAttribute("name");
out.write("您购买的是："+product);
}
把JESSIONID写到浏览器的url中
@Override
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();
request.getSession();
//添加SessionId，因为cookies的SessionId可能会被用户禁用
String url1 = response.encodeURL("/SessionDemo1");
String url2 = response.encodeURL("/SessionDemo2");
out.print("<a href="+url1+">购买</a><br/>");
out.print("<a href="+url2+">结账</a>");
}
Session 登录实例
首页： index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Heinika Web</title>
</head>
<body>
欢迎你：${user.userName}<br>
<a href="login.html">登录 </a>
<a href="/LogoutDemo">退出登录</a>
<br/>
this my first web app
</body>
</html>
登录页: login.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>登录</title>
</head>
<body>
<form action="/LoginDemo">
用户名：<input type="text" name="username"><br/>
密码：<input type="password" name="password"><br/>
<input type="submit" value="登录">
</form>
</body>
</html>
登录Servlet：
@WebServlet(name = "LoginDemo")
public class LoginDemo extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
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> users = DB.getAll();
for (User user:users){
if(user.getUserName().equals(username)&&user.getPassword().equals(password)){
request.getSession().setAttribute("user",user);
response.sendRedirect("/index.jsp");
}
}
out.write("用户名或密码不对！");
}
}
//用于模拟数据库
class DB{
public static List list = new ArrayList();
static {
list.add(new User("aaa","111"));
list.add(new User("bbb","222"));
list.add(new User("ccc","333"));
}
public static List getAll(){
return list;
}
}
退出登录：
@WebServlet(name = "LogoutDemo")
public class LogoutDemo extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession(false);
if(session == null){
response.sendRedirect("/index.jsp");
return;
}
session.removeAttribute("user");
response.sendRedirect("/index.jsp");
}
}
