1． 需要掌握的技术；

Java语言（Java database Connectivity技术、Servlet技术、jsp(Java Server Pages)技术，JavaBean(Application)应用组件技术）、面向对象分析设计思想、设计模式和框架结构、XML语言、网页脚本语言、开发工具（数据库、web服务器、集成开发环境（IDE））

程序源代码：

DBUtil.java

package com.jaovo.msg.Util;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;public class DBUtil {    public static Connection getConnection() {        try {            Class.forName("com.mysql.jdbc.Driver").newInstance();        } catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        String user = "root";        String password = "root";        String url = "jdbc:mysql://localhost:3306/jaovo_msg";        Connection connection = null;        try {            connection = DriverManager.getConnection(url, user, password);        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return connection;    }}

login.jsp

<%@page import = "com.jaovo.msg.Util.DBUtil" %><%@page import = "java.sql.*" %><%@page import = "java.sql.PreparedStatement" %><%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><%    String username = request.getParameter("username");    String password = request.getParameter("password");    if(username == null || "".equals(username.trim())){        request.setAttribute("result", "请输入用户名!");%>        
     <%    }    if(password == null || "".equals(password.trim())){        request.setAttribute("result", "请输入密码!");%>        
     <%    }    Connection connection = DBUtil.getConnection();    boolean flag = false;    String sql = "select * from t_user where username = ?";    PreparedStatement preparedstatement = null;    ResultSet resultset = null;    preparedstatement = connection.prepareStatement(sql);    preparedstatement.setString(1,username);    resultset = preparedstatement.executeQuery();    while(resultset.next()){            if(resultset.getString("password").equals(password)){                flag = true;                request.setAttribute("result", "登陆成功！");%>                <%=request.getAttribute("result")%><%            }            else{                request.setAttribute("result", "密码错误！请重新登录！");%>                
     <%            }    }    if(!flag){        request.setAttribute("result", "没有这个人！登录失败！");%>        
     <%    }%>

loginwindow.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%>        <%=request.getAttribute("result") %>    
     
        
      
                   
        
                         
用户名称：
                         
                                    
                    
                    
                         
用户密码:
                             
                                            
                    
                    
                             
                                                                            
                    
               
      
    
     

运行结果截图：

什么都不输入的情况下：

密码输入错误的情况下：

没有用户的情况下：

登录成功时：