登录系统-基于servlet

1.       新建一个web项目，在项目中添加两个包：JavaBean和Servlet。

2.       在JavaBean包中新建是三个java类：DB_Conn.java、DB_User.java和User.java。

DB_Conn.java文件用于数据库连接，加入如下代码：

package JavaBean;

 

import java.io.PrintWriter;

import java.sql.*;

 

public class DB_Conn {

      

    private  String driverName="com.mysql.jdbc.Driver";      //驱动程序名

    private  String userName="root";                         //数据库用户名

    private  String userPwd="123456";                        //密码

    private  String url="jdbc:mysql://localhost:3306/book";    //连接字符串

    private  Connection conn=null;                          //数据库连接对象

    public Statement sm=null;                               //数据库语句对象

    private PrintWriter out = null;

   

    // 建立数据库连接

    public void ConnectDB(){

            try {

                   Class.forName(driverName).newInstance();

                conn=DriverManager.getConnection(url,userName,userPwd);  //获得数据库连接

                sm=conn.createStatement();

         } catch(Exception e) {

                out.print("数据库连接失败!");

            }

    }

   

    public void CloseDB(){

           try {

                     if (sm != null) {

                            sm.close();

                     }

                     conn.close();

              } catch (SQLException SqlE) {

                     out.print("数据库关闭失败！");

              }

   

   }   

}

本实验使用的是mysql数据库，数据库名称：book，数据表名称：admin，字段名：u_id,u_Name,u_Pass。

DB_User.java文件用于数据库访问，结果保存到对象中，加入如下代码：

package JavaBean;

 

import java.sql.ResultSet;

import java.sql.SQLException;

 

public class DB_User {

      

    //创建公用数据库连接类对象

       DB_Conn db_conn=new DB_Conn();

       //通过用户名称获取用户信息

       public User get(String username, String password) {

              db_conn.ConnectDB();

              ResultSet rs = null;

              try {

                     String sql = "select * from admin where u_Name ='"

                                   + username + "' and u_Pass='" + password + "'";

                     rs = db_conn.sm.executeQuery(sql);        // 执行sql语句

                     User user = null;

                     if (rs.next()) {

                            user = new User();                     

                            user.setUsername(username);

                            user.setPassword(rs.getString("u_Pass"));                       

                            return user;

                     }

                     return user;

              }

              catch (SQLException SqlE) {

                     return null;

              }

              catch (Exception E) {

                     return null;

              }

              finally {

                     // 关闭连接，释放数据库资源：

                     db_conn.CloseDB();

              }

       }

       

      

}

User.java文件用于关系数据库到对象的映射，加入如下代码：

package JavaBean;

 

public class User {

       private String username;

       private String password;      

      

      

       public String getUsername() {                   //用户名称

              return username;

       }

       public void setUsername(String username) {

              this.username = username;

       }

      

       public String getPassword() {                   //登陆密码

              return password;

       }

       public void setPassword(String password) {

              this.password = password;

       }

      

}

3.       在Servlet包中新建servlet类：LoginServlet.java，在步骤3中选中“将信息添加到部署描述符”选项。如图：

 

 

打开web.xml文件，可以看到如下关于servlet的部署设置：

<servlet>

        <servlet-name>LogServlet</servlet-name>

        <servlet-class>Servlet.LoginServlet</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>LogServlet</servlet-name>

        <url-pattern>/LoginServlet</url-pattern>

</servlet-mapping>

在LoginServlet.java中加入如下代码：

 import JavaBean.DB_User;
import JavaBean.User;
/**
 *
 * @author skylzy
 */
public class LoginServlet extends HttpServlet {

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
          String UserName = request.getParameter("logname");
         String Password = request.getParameter("logpwd");  

   DB_User dbuser = new DB_User();
          User user = dbuser.get(UserName, Password);
         if (user != null) {
                  request.getSession(true).setAttribute("username", UserName);
                         try {
                                     request.getRequestDispatcher("index.jsp").forward(request,response);
                                }
                           catch (Throwable t) {
                                     getServletContext().log(t.getMessage());
                             }
               } else {
                        request.setAttribute("error", "用户名与密码不匹配,登录失败,请重试！");
                        try {
                                    request.getRequestDispatcher("Login.jsp").forward(request, response);
                        }
                         catch (Throwable t) {
                                        getServletContext().log(t.getMessage());
                         }
               }
    }

4.创建如下两个页面：

login.jsp

<%@ page pageEncoding="UTF-8" %>

<%@ page contentType="text/html; charset=gb2312" %>

<% request.setCharacterEncoding("gb2312"); %>

<%@ page language="java" %>

<html>  

         <head><title>登录网页</title></head>

       <body>

       <form method="POST" action="./LoginServlet">

 

       <table  >

           <tr>

             <td width="890" align="left" colspan="2">

              <b><font size="5">系统登录</font></b>

               <hr>

             </td>

           </tr>

            <% if (request.getAttribute("error") != null){ %>

       <tr>

              <td width=100% align=center colspan=4 height=36>

                   <font color=red><b><%=request.getAttribute("error")%></b></font>

              </td>

       </tr>

       <%

     }

       %>

           <tr>

             <td width="75" align="center">

               <p align="right">账号：</p>

             </td>

             <td width="809" align="center">

               <p align="left">

                <input type="text" name="logname" size="20"></td>

           </tr>

           <tr>

             <td width="75" align="center">

               <p align="right">密码：</p>

             </td>

             <td width="809" align="center">

               <p align="left">

               <input type="password" name="logpwd" size="20">

               <input type="submit" value="登录" name="loginButton"></td>

           </tr>

         </table>

       </form>

       </body>

       </html>

accesspage.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

        <title>登录成功</title>

    </head>

    <body>

        <h1>Hello

            <% if (request.getAttribute("username") != null){ %>       

              <font color=red>

                     <b>

                         <%=request.getAttribute("username")%>

                     </b>

                </font>  

            <%

                }

            %>

         !</h1>

    </body>

</html>

5.生成项目，并运行http://localhost:8080/login/login.jsp