首先创建一个用户表，用来保存用户名 密码，并插入几条数据

mysql> desc user;

+----------+-------------+------+-----+---------+----------------+

| Field | Type | Null | Key | Default | Extra |

+----------+-------------+------+-----+---------+----------------+

| id | int(11) | NO | PRI | NULL | auto_increment |

| username | varchar(20) | YES | | NULL | |

| password | varchar(50) | YES | | NULL | |

+----------+-------------+------+-----+---------+----------------+

创建语句，注意一定要设置password的长度超过41，因为插入数据时我们使用password函数，生成长度为41的字符串，

例如：

mysql> select password('aasas');

+-------------------------------------------+

| password('aasas') |

+-------------------------------------------+

| *462034BF6D04324F93F1F6CA352B23079A165972 |

+-------------------------------------------+

1 row in set (0.00 sec)

mysql> select length( password('aasas'));

+----------------------------+

| length( password('aasas')) |

+----------------------------+

| 41 |

+----------------------------+

1 row in set (1.76 sec)

CREATE TABLE `user` (

`id`int(11) NOT NULLAUTO_INCREMENT,

`username`varchar(20) DEFAULT NULL,

`password`varchar(50) DEFAULT NULL,PRIMARY KEY(`id`)

) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

插入数据：

mysql> insert into user(username,password) values('root',password('root'));

查看一下插入结果：此时密码已经变成一串字符串.

mysql> select * from user where username='root';

+----+----------+-------------------------------------------+

| id | username | password |

+----+----------+-------------------------------------------+

| 4 | root | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |

+----+----------+-------------------------------------------+

1 row in set (0.00 sec)

2.创建一个java web project，新建一个名为user的类,使用jdbc链接数据库，把user表的数据拿出来和输入的用户名密码对比，并添加validate方法

如果用户名密码正确，返回true。之后注意将Mysql JDBC的driver copy到lib目录下，否则无法运行

packagecom.data;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.PreparedStatement;importjava.sql.ResultSet;public classuser {private staticString userName;private staticString password;publicString getUserName() {returnuserName;

}public voidsetUserName(String userName) {this.userName =userName;

}publicString getPassword() {returnpassword;

}public voidsetPassword(String password) {this.password =password;

}public static booleanvalidate()

{

String url= "jdbc:mysql://localhost:3306/study";

String user= "root";

String dbpassword= "3edc4rfv";boolean result = false;try{

String driver="com.mysql.jdbc.Driver";

Class.forName(driver);

Connection con=DriverManager.getConnection(url,user, dbpassword);if(con==null){

System.out.println("can't open DBConnection");

}

String sql= "select * from user where username=? and password=password(?)";

PreparedStatement pstmt=con.prepareStatement(sql);

pstmt.setString(1, userName);

pstmt.setString(2, password);

System.out.println(sql);

ResultSet rs=pstmt.executeQuery();if(rs.next())

{

System.out.println("PASS");

result=true;

}else{

System.out.println("FAIl");

result=false;

}

pstmt.close();

rs.close();

con.close();

}catch(Exception e) {//TODO Auto-generated catch block

e.printStackTrace();

}returnresult;

}

}

并新建一个Servlet，包名com.web，class name login.java，这里主要使用post方法，所以在dopost方法添加代码

将login.java 修改为这样：

packagecom.web;importjava.io.IOException;importjava.io.PrintWriter;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.PreparedStatement;importjava.sql.ResultSet;importjava.util.ArrayList;importjava.util.List;importjavax.servlet.ServletException;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importcom.data.book;importcom.data.user;public class login extendsHttpServlet {/*** Constructor of the object.*/

publiclogin() {super();

}/*** Destruction of the servlet.
*/

public voiddestroy() {super.destroy(); //Just puts "destroy" string in log//Put your code here

}/*** The doGet method of the servlet.

*

* This method is called when a form has its tag value method equals to get.

*

*@paramrequest the request send by the client to the server

*@paramresponse the response send by the server to the client

*@throwsServletException if an error occurred

*@throwsIOException if an error occurred*/

public voiddoGet(HttpServletRequest request, HttpServletResponse response)throwsServletException, IOException {//Add some codes

doPost(request,response);

}/*** The doPost method of the servlet.

*

* This method is called when a form has its tag value method equals to post.

*

*@paramrequest the request send by the client to the server

*@paramresponse the response send by the server to the client

*@throwsServletException if an error occurred

*@throwsIOException if an error occurred*/

public voiddoPost(HttpServletRequest request, HttpServletResponse response)throwsServletException, IOException {

request.getParameter("username");

request.getParameter("password");

request.getSession().setAttribute("user", request.getParameter("username")); //将user放在Attribute中

user user1=newuser();

user1.setUserName(request.getParameter("username"));

user1.setPassword(request.getParameter("password"));

System.out.println(request.getParameter("username")+request.getParameter("password"));if(user1.validate())

{request.getRequestDispatcher("welcome.jsp").forward(request, response); //校验用户名密码正确，跳转到welcome.jsp

}else{

request.getRequestDispatcher("index.jsp").forward(request, response); //校验用户名密码不正确，跳转到index.jsp

}

}/*** Initialization of the servlet.

*

*@throwsServletException if an error occurs*/

public void init() throwsServletException {//Put your code here

}

}

此时web.xml代码如下。可以使用login.do访问这个Servlet

http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

login Page

login Page

login

com.web.login

login

/login.do

index.jsp

3.在jsp页面添加相应的action，在index.jsp的body标签之间添加，会生出登录界面，用户名 密码

username

password

4.添加welcome.jsp

在welcome.jsp body标签添加

Welcome

5.加载工程