1、login.jsp
- login.jsp中
username和password在LoginSelect.jsp验证是否一致
- 使用
session.setAttribute("login_msg","用户名或密码为空")设置login_msg的值
- 使用
session.getAttribute("login_msg")获取对象的值，判断输入框是否为空，如果为空，则提示用户名或密码为空。
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录界面</title>
</head>
<body>
<div align="center">
<h1>欢迎登录</h1>
<form action="LoginSelect.jsp" method="post" id="form">
<p>用户名: <input id="username" name="username" type="text">  </p>
<p>密码: <input id="password" name="password" type="password"></p>
<input type="submit" class="button" value="登录" onclick="">
<button><a href="register.jsp">注册</a></button>
</form>
<div id="errorMsg" value="null"><%=session.getAttribute("login_msg")%></div>
</div>
<script>
if(document.getElementById("errorMsg").innerText==="null"||document.getElementById("errorMsg").innerText===""){
document.getElementById("errorMsg").setAttribute('style',"display:none")
} else {
document.getElementById("errorMsg").setAttribute('style',"display:block")
}
</script>
</body>
</html>
2、 loginSelect.jsp
- 利用Map集合存储账户和密码信息，模拟数据库
map.put("20201234","123456")设置初始数据map.put(username,session.getAttribute(username).toString())这里是将注册的账户和密码添加到数据库中，username为键，session.getAttribute(username).toString()为值，两者都为字符串类型
<%@ page import="java.util.*" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>判断登录界面</title>
</head>
<body>
<%!
Map<String,String> map = new HashMap<String,String>();
public boolean compare(String username,String password){
String pwd = map.get(username);
if(pwd!=null&&password.equals(pwd)){
return true;
}
else{
return false;
}
}
%>
<%
String username = request.getParameter("username");
String password = request.getParameter("password");
//设置初始值
map.put("20201234","123456");
//注册后的值存入map集合
if (session.getAttribute(username)!=null){
map.put(username,session.getAttribute(username).toString());
}
System.out.println(map);
//判断输入内容是否正确,给出提示信息
if (username==null||username =="" || password==null || password==""){
session.setAttribute("login_msg","用户名或密码为空");
response.sendRedirect("login.jsp");
return;
}
boolean compare = compare(username, password);
if (compare){
session.setAttribute("username",username);
session.setAttribute("password",password);
response.sendRedirect("index.jsp");
}
else {
session.setAttribute("login_msg","用户名或密码错误或用户名不存在");
response.sendRedirect("login.jsp");
}
%>
</body>
</html>
3、register.jsp
- register.jsp中
username和password在RegisterSelect.jsp验证是否一致
- 使用
session.setAttribute("register_msg","用户名或密码为空")设置register_msg的值
- 使用
session.getAttribute("register_msg")获取对象的值，判断输入框是否为空，如果为空，则提示用户名或密码为空。
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>注册界面</title>
</head>
<div align="center">
<h1>欢迎注册</h1>
<form action="RegisterSelect.jsp" method="post">
<table>
<tr>
<td>用户名</td>
<td>
<input name="username" type="text" id="username">
<br>
</td>
</tr>
<tr>
<td>密码</td>
<td>
<input name="password" type="password" id="password">
<br>
</td>
</tr>
</table>
<input value="注 册" type="submit" id="reg_btn"><br>
<span>已有帐号？</span> <a href="login.jsp">登录</a>
</form>
<span id="register_msg" class="err_msg" ><%=session.getAttribute("register_msg")%></span>
</div>
</body>
</div>
<script>
if(document.getElementById("register_msg").innerText==="null"||document.getElementById("register_msg").innerText===""){
document.getElementById("register_msg").setAttribute('style',"display:none")
} else {
document.getElementById("register_msg").setAttribute('style',"display:block")
}
</script>
</html>
4、 RegisterSelect.jsp
if else语句，if 判断账户或密码为空则提示"用户或密码为空"，else 使用session.setAttribute(username,password) 创建对象存储新的账户和密码信息。
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%
String username = request.getParameter("username");
String password = request.getParameter("password");
session.setAttribute("register_msg","null");
if (username==null||username =="" || password==null || password==""){
session.setAttribute("register_msg","用户名或密码为空");
response.sendRedirect("register.jsp");
return;
}
else {
session.setAttribute(username,password);
response.sendRedirect("login.jsp");
}
%>
<html>
<head>
<title>Title</title>
</head>
<body>
</body>
</html>
5、 index.jsp
session.getAttribute("username")动态获取账户名称
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录成功</title>
</head>
<body>
<div align="center">
<h1>JSP管理系统</h1>
<h1><%=session.getAttribute("username")%> 欢迎您!</h1>
<a href="login.jsp">退出登录</a>
</div>
</body>
</html>