如何在输入错误的用户名和/或密码时将用户从登录控件重定向到错误页面
How to redirect user to an error page from login control upon entering wrong username and/or password?
我创建了一个登录表单，当我使用正确的用户名和密码登录时，它工作正常。我想在输入错误的用户名或密码时弹出错误消息或错误页面。这意味着控制器会将给定的用户名与数据库中的所有用户名进行比较，如果未找到给定的用户名，则应显示错误消息或错误页面。
如何使用 HTML 或 JavaScript 执行此操作？ 有没有办法在 servlet 中创建一个简单的错误消息？但我需要再次重新加载页面。
<html>
<body>
<form action="search" onsubmit="return validateForm()">
<table>
<tr><td>Username</td>
<td><input type=text name=LoginId /></td>
</tr>
<tr><td>Password</td>
<td><input type=password name=LoginPassword /> </td>
</tr>
<tr>
<td colspan=2>
<center>
<input type=submit value=SignIn /><br>If you forgot your password, <a href="ResetPassword"> Reset </a>your password.
</center>
</td>
</tr>
</table>
</form>
</body>
</html>
SearchServlet.java
/**
* @see HttpServlet#HttpServlet()
*/
public SearchServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
CustomerDAO customerDAO = new CustomerDAO();
String username = request.getParameter("LoginId");
String password = request.getParameter("LoginPassword");
Login login = customerDAO.getLoginByName(username, password);
PrintWriter out = response.getWriter();
out.println("<html><body>");
out.println("<center><h1>User Information</h1></center>");
out.println("<center><table border=0x>");
out.println("<tr>");
out.println("<td>Login Id : </td><td>"+login.getLoginId()+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>City : </td><td>"+login.getCity()+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>State : </td><td>"+login.getState()+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Cell Number : </td><td>"+login.getCellnumber()+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Email :</td><td>"+login.getEmail()+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Address :</td><td>"+login.getAddress()+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>ZipCode : </td><td>"+login.getZipcode()+"</td>");
out.println("</tr>");
out.println("</table></center>");
out.println("<p>If these details are correct press continue or to change your information press update.</p>");
out.println("<form action='Continue.jsp'>");
out.println("<center><input type=submit value=continue></center>");
out.println("</form>");
out.println("<form action='search'>");
out.println("<center><a href=Update?City="+login.getCity()+"&State="+login.getState()+"&PhoneNumber="+login.getCellnumber()+"&Email="+login.getEmail()+"&Address="+login.getAddress()+"&ZipCode="+login.getZipcode()+"> update </a></center>");
out.println("</form>");
out.println("</body></html>");
Login l = new Login();
l.setLoginId(request.getParameter("LoginId"));
if(l!=null) {
HttpSession session = request.getSession();
session.setAttribute("l", l);
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
客户道.java
public class CustomerDAO extends BaseDAO{
public Login getLoginByName(String username, String password) {
Login login = null;
try {
BaseDAO baseDAO = new BaseDAO();
Connection c =baseDAO.getConnection();
// String query = "select * from test.Login where LoginId=? && LoginPassword=?";
String query = "select * from test.Customer where LoginId=? && LoginPassword=?";
PreparedStatement ps = c.prepareStatement(query);
ps.setString(1, username);
ps.setString(2, password);
ResultSet rs = ps.executeQuery();
while(rs.next()) {
login = new Login();
login.setLoginId(rs.getString("LoginId"));
login.setCity(rs.getString("City"));
login.setState(rs.getString("State"));
login.setCellnumber(rs.getString("PhoneNumber"));
login.setEmail(rs.getString("Email"));
login.setAddress(rs.getString("Address"));
login.setZipcode(rs.getInt("ZipCode"));
System.out.println();
}
c.close();
}catch(Exception e) {
System.err.println("Username or Password you enterd is incorrect.");
}
return login;
}
登录.java
package com.dao;
public class Login {
String LoginId;
String password;
String confirmpassword;
String city;
String state;
String cellnumber;
int zipcode;
String Email;
String Address;
public Login() {
// TODO Auto-generated constructor stub
}
public String getLoginId() {
return LoginId;
}
public void setLoginId(String loginId) {
LoginId = loginId;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getConfirmpassword() {
return confirmpassword;
}
public void setConfirmpassword(String confirmpassword) {
this.confirmpassword = confirmpassword;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getCellnumber() {
return cellnumber;
}
public void setCellnumber(String cellnumber) {
this.cellnumber = cellnumber;
}
public int getZipcode() {
return zipcode;
}
public void setZipcode(int zipcode) {
this.zipcode = zipcode;
}
public void setEmail(String email) {
Email = email;
}
public String getEmail() {
return Email;
}
public void setAddress(String address) {
Address = address;
}
public String getAddress() {
return Address;
}
}
在此之后：
PrintWriter out = response.getWriter();
添加 ->
if (login == null){
out.println("<html><body>");
out.println("<center><h1>Login failed, wrong username or password</h1></center>");
out.println("</body>");
out.println("<script type='text/javascript'>");
out.println("function reload() {");
out.println("setTimeout(function(){");
out.println("window.location = '"+request.getContextPath()+"/search';}");
out.println("}, 5000);");
out.println("reload();");
out.println("</script>");
out.println("</html>");
}
}
但这是一种糟糕的身份验证方式，您必须编写自己的授权过滤器，这是很多冗余代码，而不是使用 Web 容器身份验证机制 请参阅保护 Web 应用
它很容易覆盖，可以添加自定义登录，添加软登录，角色和类似的东西。
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