JSP登录案例之session应用
简介：
创建login.jsp提交用户名和密码，创建ASerlet进行用户名和密码的校验，创建source1.jsp、source2.jsp作为访问界面，流程如下；
AServlet：
package demoServlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet("/AServlet")
public class AServlet extends HttpServlet {
@Override
public void init() throws ServletException {
System.out.println("出生啦！！");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
// 获取用户名和密码
String username = req.getParameter("username");
String password = req.getParameter("password");
// 获取session
HttpSession session = req.getSession();
// 校验用户名和密码
if("cdml".equals(username)) { // 判断用户名
if("qwe".equals(password)) { // 判断密码
// 用户名和密码都正确，设置用户名和密码
session.setAttribute("username", username);
session.setAttribute("password", password);
// 设置Cookie
Cookie cookie = new Cookie("username", username);
cookie.setMaxAge(60*60*24); // cookie有效时间为一天
resp.addCookie(cookie); // 添加cookie
// 重定向
resp.sendRedirect("/day0421_session/jsp/source1.jsp");
}else {
// 设置错误密码
req.setAttribute("password", password);
// 转发
req.getRequestDispatcher("/jsp/login.jsp").forward(req, resp);
}
}else {
// 设置错误用户名
req.setAttribute("username", username);
// 转发
req.getRequestDispatcher("/jsp/login.jsp").forward(req, resp);
}
}
}
login.jsp:
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录title>
head>
<body>
<div align="center">
<%
/*
读取名为username的cookie
*/
Cookie[] cookies = request.getCookies();
String uname = "";
if (cookies != null) {
for (Cookie c : cookies) {
if ("username".equals(c.getName())) {
uname = c.getValue();
out.print("您上次登录的账号是：
" + c.getValue() + "
");
break;
}
}
}
%>
<form action="/day0421_session/AServlet" method="post">
用户名: <input type="text" name="username" value=<%=uname %>><br />
密码 : <input type="text" name="password"><br />
<input type="submit" value="提交">
form>
<font color="red"><b>
<%
Object username = request.getAttribute("username");
Object password = request.getAttribute("password");
String nousername = (String) request.getAttribute("nousername");
if (username != null) {
out.print("
用户名：" + username.toString() + " 错误!!
请重试！！！");
} else if (password != null) {
out.print("
密码：" + password.toString() + " 错误!!
请重试！！！");
}
if (nousername != null) { // 不为空则跨过了登录界面
if ("ture".equals(nousername)) { // 跨过了登录界面
out.print("请先登录！");
}
}
%>
b>font>
div>
body>
html>
source1.jsp:
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>页面一title>
head>
<body>
<div align="center">
<h1>成功登录h1>
<%
Object username = session.getAttribute("username");
if (username != null) { // 用户名不为空
out.print("欢迎您！用户：" + username + ", 早上好！");
}else{ // 用户名为空
request.setAttribute("nousername", "ture"); // 设置越界信息
request.getRequestDispatcher("/jsp/login.jsp").forward(request, response); // 转发，不是重定向是因为越界信息设置在request上的，所以需要转发将request传递过去
}
%>
<br/> <a href="
source2.jsp:
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>source2title>
head>
<body>
<div align="center">
<h1>成功登录h1>
<%
Object username = session.getAttribute("username");
if (username != null) { // 用户名不为空
out.print("欢迎您！用户：" + username + ", 早上好！这里是source2！");
}else{ // 用户名为空
request.setAttribute("nousername", "ture"); // 设置越界信息
request.getRequestDispatcher("/jsp/login.jsp").forward(request, response); // 转发，不是重定向是因为越界信息设置在request上的，所以需要转发将request传递过去
}
%>
div>
body>
html>
输入预定的账号密码：cdml、qwe
点击提交：
也可以转到source2.jsp页面，提示：source2.jsp页面使用的EL表达式，需要导入指定的包