Detailed Explanation of JSP+Servlet+JavaBean Implementation of Login Web Page Example
- 2021-07-09 09:02:06
- OfStack
This paper describes the method of JSP+Servlet+JavaBean to login web pages. Share it for your reference. The details are as follows:
There are four files involved here:
1. Login page: login. html
2. Welcome page for successful login: login_success. jsp
3. Login Failure Page: login_failure. jsp
4. Servlet processing file: LoginServlet. java
In fact, there is also a file involved: web. xml, which will be discussed later:
These files are described below:
1. Login page: login. html
<!-- The Login The page is 1 Simple login interface -->
<!--
The JSP The program is used to test and compare with MySQL Database connection,
Need 1 Databases: LearnJSP , and among them 1 Tables: userinfo
There are two fields in the table: UserName varchar (20) not null,UserPwd varchar (20) not null
-->
<html>
<head>
<title> Login </title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<meta http-equiv="Content-Language" content="ch-cn">
</head>
<body>
<!-- Form Used to extract the information filled in and submitted by the user -->
<form method="post" name="frmLogin" action="LoginServlet">
<h1 align="center"> User login </h1><br>
<div align="center"> User name:
<input type="text" name="txtUserName" value="Your name"
size="20" maxlength="20"
onfocus="if(this.value=='Your name')this.value='';"><br> Password:
<input type="password" name="txtPassword" value="Your password"
size="20" maxlength="20"
onfocus="if(this.value=='Your password')this.value='';"><br>
<input type="submit" name="Submit" value=" Submit " onClick="validateLogin();" >
<input type="reset" name="Reset" value=" Reset "><br>
</div>
</form>
<!-- javaScript Function validateLogin(), Used to verify that the username and password are empty -->
<script language="javaScript">
function validateLogin()
{
var sUserName = document.frmLogin.txtUserName.value;
var sPassword = document.frmLogin.txtPassword.value;
if( sUserName=="" )
{
alert(" Please enter the user name! ");
return false;
}
if( sPassword=="" )
{
alert(" Please enter the password! ");
return false;
}
}
</script>
</body>
</html>
2. Welcome page for successful login: login_success. jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'login_failure.jsp' starting page</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<%
String userName = (String)session.getAttribute ( "UserName" );
%>
<div align=center>
<%=userName%>
Welcome, login is successful!
</div>
</body>
</html>
3. Login Failure Page: login_failure. jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'login_failure.jsp' starting page</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<%
String userName = (String)session.getAttribute ( "UserName" );
%>
<div align=center>
<%=userName%>
Sorry, login failed!
</div>
</body>
</html>
4. Servlet processing file: LoginServlet. java
/**
* The JSP The program is used to test and compare with MySQL Database connection,
* Need 1 Databases: LearnJSP , and among them 1 Tables: userinfo
* There are two fields in the table: UserName varchar (20) not null,UserPwd varchar (20) not null
*/
package zieckey.login.servlet;
import java.sql.Statement;
import java.io.IOException;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet implements Servlet
{
public LoginServlet ()
{
// TODO Auto-generated constructor stub
}
/*
* (non-Javadoc)
*
* @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest,
* javax.servlet.http.HttpServletResponse)
*/
@Override
protected void doGet ( HttpServletRequest arg0, HttpServletResponse arg1 )
throws ServletException, IOException
{
}
/*
* (non-Javadoc)
*
* @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest,
* javax.servlet.http.HttpServletResponse)
*/
@Override
protected void doPost ( HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
response.setContentType ( "text/html" );
String result = "";
// Get User Name
String sUserName = request.getParameter ( "txtUserName" );
if ( sUserName == "" || sUserName == null || sUserName.length ( ) > 20 )
{
try
{
result = " Please enter a user name (no more than 20 Characters)! ";
request.setAttribute ( "ErrorUserName", result );
response.sendRedirect ( "login.html" );
} catch ( Exception e )
{
}
}
// Get the password
String sPasswd = request.getParameter ( "txtPassword" );
if ( sPasswd == "" || sPasswd == null || sPasswd.length ( ) > 20 )
{
try
{
result = " Please enter your password (no more than 20 Characters)! ";
request.setAttribute ( "ErrorPassword", result );
response.sendRedirect ( "login.html" );
} catch ( Exception e )
{
}
}
// Registration JDBC Driver
try
{
Class.forName ( "org.gjt.mm.mysql.Driver" ).newInstance ( );
} catch ( InstantiationException e )
{
// TODO Auto-generated catch block
e.printStackTrace ( );
System.out.println ("InstantiationException");
} catch ( IllegalAccessException e )
{
// TODO Auto-generated catch block
e.printStackTrace ( );
System.out.println ("IllegalAccessException");
} catch ( ClassNotFoundException e )
{
// TODO Auto-generated catch block
e.printStackTrace ( );
System.out.println ("ClassNotFoundException");
}
// Connection parameters and Access Different
String url = "jdbc:mysql://localhost/LearnJSP";
// Establish a connection
java.sql.Connection connection = null;
Statement stmt = null;
ResultSet rs = null;
try
{
connection = DriverManager.getConnection ( url, "root", "011124" );
stmt = connection.createStatement ( );
// SQL Statement
String sql = "select * from userinfo where username='" + sUserName
+ "' and userpwd = '" + sPasswd + "'";
rs = stmt.executeQuery ( sql );// Return query results
} catch ( SQLException e )
{
// TODO Auto-generated catch block
e.printStackTrace ( );
}
try
{
if ( rs.next ( ) )// If the recordset is not empty, it indicates that there is a matching username and password, and the login is successful
{
// After successful login, the sUserName Set to session Variable UserName
// So that you can pass in the back session.getAttribute("UserName") To get the user name,
// At the same time, it can also be used as the basis for judging whether users log in or not
request.getSession ( ).setAttribute ( "UserName", sUserName );
response.sendRedirect ( "login_success.jsp" );
} else
{
// Otherwise login fails
//response.sendRedirect ( "MyJsp.jsp" );
response.sendRedirect ( "login_failure.jsp" );
}
} catch ( SQLException e )
{
// TODO Auto-generated catch block
e.printStackTrace ( );
}
try
{
if ( null!=rs )
{
rs.close ( );
}
if ( null!=stmt )
{
stmt.close ( );
}
if ( null!=connection )
{
connection.close ( );
}
} catch ( SQLException e )
{
// TODO Auto-generated catch block
e.printStackTrace ( );
}
}
/**
*
*/
private static final long serialVersionUID = 1L;
}
In order to make this website run normally, you have to register 1 in web. xml.
The contents of this document are now revised as follows:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.4" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<display-name>LoginServlet</display-name>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>zieckey.login.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>
</web-app>
Ok, these files can form our login interface.
Precautions:
1. Document directory form
login. html, login_success. html and login_failure. html are placed in the same directory.
LoginServlet. java the bytecode file for this file, LoginServlet. class, is placed in the WEB-INF/classes directory (note the jar packet order)
Now the directory form of the whole project is:
Directory for M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login
007-01-18 15:16
<
DIR
>
META-INF
007-01-18 15:16
<
DIR
>
WEB-INF
007-01-18 16:17 1,801 login.html
007-01-18 15:48 858 login_failure.jsp
007-01-18 15:40 234 login_success.html
007-01-18 15:46 781 MyJsp.jsp
007-01-18 16:12 859 login_success.jsp
Directory for M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login/WEB-INF
007-01-18 15:16
<
DIR
>
classes
007-01-18 15:16
<
DIR
>
lib
007-01-18 16:21 606 web.xml
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login/WEB-INF/classes/zieckey/login/servlet
2007-01-18 16:18 3,900 LoginServlet.class
2. Other considerations
The database MySQL server program should be started first.
I hope this article is helpful to everyone's JSP programming.