Session簡介
Session是服務端技術，利用這個技術。利用這個技術，伺服器在執行時可以為每一個使用者的瀏覽器建立一個獨享的session物件，由於Session為使用者瀏覽器獨享，所以使用者在訪問瀏覽器資源時，可以把各自的資料放在各自的session中，當使用者再去訪問伺服器的其他web資源時，其他web資源再從使用者各自的session中取出資料為使用者服務。
建立或獲取Session，並以Cookie的方式回寫JSESSIONID。
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
//Session的另外一種獲取方式，這種方式只獲取不建立。比如檢視購物車的操作，如果使用者沒有購物的話，沒有必要建立一個Session。
// request.getSession(false);
String sessionid = session.getId();
Cookie cookie = new Cookie("JSESSIONID",sessionid);
cookie.setPath("/");
//設定cookie的儲存時長為30分鐘，因為Session一般就在伺服器中儲存30分鐘，多了也沒用。。。
cookie.setMaxAge(30*60);
response.addCookie(cookie);
session.setAttribute("name","洗衣機");
}
複製程式碼獲取Session中的內容
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("您購買的是："+product);
}
複製程式碼把JESSIONID寫到瀏覽器的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();
//新增SessionId，因為cookies的SessionId可能會被使用者禁用
String url1 = response.encodeURL("/SessionDemo1");
String url2 = response.encodeURL("/SessionDemo2");
out.print("<a href="+url1+">購買</a><br/>");
out.print("<a href="+url2+">結賬</a>");
}
複製程式碼Session 登入例項
首頁： index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Heinika Web</title>
</head>
<body>
歡迎你：${user.userName}<br>
<a href="login.html">登入 </a>
<a href="/LogoutDemo">退出登入</a>
<br/>
this my first web app
</body>
</html>
複製程式碼登入頁: login.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>登入</title>
</head>
<body>
<form action="/LoginDemo">
使用者名稱：<input type="text" name="username"><br/>
密碼：<input type="password" name="password"><br/>
<input type="submit" value="登入">
</form>
</body>
</html>
複製程式碼登入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("使用者名稱或密碼不對！");
}
}
//用於模擬資料庫
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;
}
}
複製程式碼退出登入：
@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");
}
}
複製程式碼