Servlet – 登录表单

使用Java，我们可以准备用于注册/登录应用程序的优雅网页，并且在获得授权的身份验证凭据后，可以看到其余的应用程序屏幕。因此，有一个登录表单来接受用户的输入然后验证数据是非常重要的。为了验证数据，我们可以在客户端使用 javascript。即像验证强制输入（需要用户名/需要密码）/如果用户名是电子邮件模式，则需要验证输入的文本是否满足电子邮件模式等，

客户端验证结束后，将根据数据库存储的数据检查输入的凭据。此过程只能在服务器端完成。这意味着这些类型的验证需要作为请求发送到服务器，并且代码需要用 Servlet 编写。通常，由于登录表单凭据很敏感，并且在传递时应该隐藏，因此它必须作为 POST 方法发送。在本文中，让我们看看我们可以设计一个基本的登录表单并通过 servlet 进行处理。让我们看看实现此功能所需的页面

login.jsp 文件：

HTML

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>



Login Application

 


body {font-family: Arial, Helvetica, sans-serif;}
form {border: 3px solid #f1f1f1;}
 
input[type=text], input[type=password] {
  width: 100%;
  padding: 12px 20px;
  margin: 8px 0;
  display: inline-block;
  border: 1px solid #ccc;
  box-sizing: border-box;
}
 
button {
  background-color: #04AA6D;
  color: white;
  padding: 14px 20px;
  margin: 8px 0;
  border: none;
  cursor: pointer;
  width: 100%;
}
 
button:hover {
  opacity: 0.8;
}
 
.cancelbutton {
  width: auto;
  padding: 10px 18px;
  background-color: #f44336;
}
 
.container {
  padding: 16px;
}
 
span.psw {
  float: right;
  padding-top: 16px;
}
 
/* Change styles for span and cancel button
   on extra small screens */
@media screen and (max-width: 300px) {
  span.psw {
     display: block;
     float: none;
  }
  .cancelbutton {
     width: 100%;
  }
}

   

 


function ValidateEmail(emailId)
{
    var mailformat = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;
    if(emailId.value.match(mailformat))
    {
        document.getElementById('password').focus();
        return true;
    }
    else
    {
        alert("You have entered an invalid email address!");
        document.getElementById('emailId').focus();
        return false;
    }
}

 



 
    
    
         
    Email
    
 
    Password
    
         
    Login
    
       Remember me
    
  
 
  
    Cancel
    Forgot password?
  
    

输出：

客户端验证输出：

在成功的客户端验证和服务器端验证后，可以看到下面的屏幕

为了执行上述步骤，我们需要一个 servlet，并让我们将其作为LoginServlet。Java

Java

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
 
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
   
    private static final long serialVersionUID = 1L;      
   
    public LoginServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
   
    // From login.jsp, as a post method only the credentials are passed
    // Hence the parameters should match both in jsp and servlet and
      // then only values are retrieved properly
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // We can able to get the form data by means of the below ways.
        // Form arguments should be matched and then only they are recognised
        // login.jsp component names should match and then only
          // by using request.getParameter, it is matched
        String emailId = request.getParameter("emailId");
        String password = request.getParameter("password");
        // To verify whether entered data is printing correctly or not
        System.out.println("emailId.." + emailId);
        System.out.println("password.." + password);
        // Here the business validations goes. As a sample,
          // we can check against a hardcoded value or pass
          // the values into a database which can be available in local/remote  db
        // For easier way, let us check against a hardcoded value
        if (emailId != null && emailId.equalsIgnoreCase("[e-mail]") && password != null && password.equalsIgnoreCase("admin")) {
            // We can redirect the page to a welcome page
            // Need to pass the values in session in order
              // to carry forward that one to next pages
            HttpSession httpSession = request.getSession();
            // By setting the variable in session, it can be forwarded
            httpSession.setAttribute("emailId", emailId);
            request.getRequestDispatcher("welcome.jsp").forward(request, response);
        }
    }
}

欢迎.jsp 文件：

HTML

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>




Welcome <%=session.getAttribute("emailId") %>

在少数情况下，我们可能会忘记密码，因此应该有可用的规定来做到这一点。我们应该有一个forgotpassword.jsp来实现这一点

HTML

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>









 
    

        

          Enter your email in order to check in our records
          
 
          Search
         
 
    

输出：

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