Java web：JSP实现登录界面，DBUtils，EL表达式，个人理解【诗书画唱】
用JSP等的知识做出个登录界面（自己写的题目）
个人的理解：因为form表单中要用上action，所以可以取前3个字母的缩写act当用户名，账号名
create table user(
id int primary key auto_increment,
act varchar(100) ,
pwd varchar(100)
);
--drop table user
insert into user(act,pwd) values ("诗书画唱",'666'),("三连",'233'),("关注",'888' );
select * from user
如果是手建的话，导出来有时看你自己的设计会为（红色部分比较有用，其他的没太多的用处）：
/*
Navicat MySQL Data Transfer
Source Server : mysql
Source Server Version : 50639
Source Host : localhost:3306
Source Database : j190802
Target Server Type : MYSQL
Target Server Version : 50639
File Encoding : 65001
Date: 2020-09-14 11:00:08
*/
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `user`
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`act` varchar(30) DEFAULT NULL,
`pwd` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES ('1', 'admin2020', '123456');
但是我更喜欢用代码建表，就用我前面的建的表的内容：
package com.xhj.bean;
//bean的类名于表的名字一致，而且首字母必须大写
public class User {
//bean类中的属性名应该和表中的列名一致
private Integer id;
private String act;
private String pwd;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getAct() {
return act;
}
public void setAct(String act) {
this.act = act;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
}
package com.xhj.DAO;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.xhj.Utils.DBUtils;
import com.xhj.bean.User;
//Dao是数据访问的意思，
//在这个类中负责对user表进行增删改查的功能实现
//Dao类中的方法就是负责执行sql语句，
//只要有执行sql语句的代码都必须写在dao类中
public class UserDao {
public User selectByActAndPwd
(String act,String pwd){
String sql = "select * "
+ "from User where act = ? and pwd = ?";
Connection conn = null;
PreparedStatement pstm = null;
ResultSet rs = null;
User u = new User();
try {
conn = DBUtils.getConn();
pstm = conn.prepareStatement(sql);
//设置占位符
pstm.setString(1, act);
pstm.setString(2, pwd);
rs = pstm.executeQuery();
if(rs.next()) {
Integer id = rs.getInt("id");
u.setId(id);
u.setAct(act);
u.setPwd(pwd);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
//清理资源
DBUtils.close(rs, pstm, conn);
}
return u;
}
public static void main(String[] args) {
UserDao ud = new UserDao();
User u = ud.selectByActAndPwd("诗书画唱", "666");
if(u.getId() != null && u.getId() > 0) {
System.out.println("登录成功");
} else {
System.out.println("登录失败");
}
}
}
package com.xhj.Utils;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Properties;
public class DBUtils {
private static String driverName;
private static String url;
private static String user;
private static String pwd;
static {
//读取properties文件
Properties prop = new Properties();
//将db.properties文件读取到内存中去
InputStream is = DBUtils.class.getClassLoader()
.getResourceAsStream("db.properties");
//加载内容
try {
prop.load(is);
//读取内容
driverName = prop.getProperty("dn");
//System.out.println(driverName);
url = prop.getProperty("url");
user = prop.getProperty("un");
pwd = prop.getProperty("up");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//获取数据库连接对象的方法
public static Connection getConn(){
Connection conn = null;
try {
Class.forName(driverName);
conn = DriverManager.getConnection(url,user,pwd);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
public static void close(ResultSet rs,
PreparedStatement pstm
,Connection conn){
try {
if(rs != null) {
rs.close();
}
if(pstm != null) {
pstm.close();
}
if(conn != null) {
conn.close();
}
} catch(Exception e) {
e.printStackTrace();
}
}
}
dn=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/firstjsp?useUnicode=true&characterEncoding=UTF-8
un=root
up=root
<%@ page language="java" contentType="text/html;
charset=UTF-8" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()
+"://"+request.getServerName()
+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC"-//W3C//DTD HTML 4.01
Transitional//EN">
<html>
<head>
<base hreff="<%=basePath%>">
<title></title>
<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">
<style type="text/css">
*{
font-size:50px;
}
</style>
</head>
<body>
<%-- 要记住dologin.jsp不要些错为doLogin.jsp
，action中的内容的大小不可以写错不然会报错等
--%>
<form action="dologin.jsp" method="post">
<table border="1">
<tr>
<td>账号：</td>
<td><input type="text" name="act"
placeholder="请输入账号"/></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password"
name="pwd" /></td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit"
value="提交" />
</td>
</tr>
</table>
<div>${msg }</div>
</form>
</body>
</html>
<%@page import="com.xhj.bean.User"%>
<%@page import="com.xhj.DAO.UserDao"%>
<%@ page language="java" contentType="text/html;
charset=UTF-8" pageEncoding="UTF-8"%>
<%
//中文乱码处理：
request.setCharacterEncoding("utf-8");
//1、获取用户输入的账号和密码：
String act = request.getParameter("act");
String pwd = request.getParameter("pwd");
System.out.println(act);
//2、查询数据库：
UserDao userDao = new UserDao();
User u = userDao.selectByActAndPwd(act, pwd);
//3、根据查询出来的结果进行处理
if(u.getId() != null && u.getId() > 0) {
//将登录的账号存放到session
//后面当你跳转到任何的页面时，
//还需要验证是否是合法的访问
request.getSession().setAttribute
("userName", act);
//a、根据账号和密码能够查询记录，就表示登录成功，
//跳转到后台管理页面
request.getRequestDispatcher
("manage.jsp").forward(request, response);
} else {
String msg = "账号或者密码错误";
request.setAttribute("msg", msg);
//b、没有查询到记录，就表示登录失败，跳转回login.jsp
request.getRequestDispatcher("login.jsp")
.forward(request, response);
}
%>
<%@ page language="java" contentType=
"text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()
+"://"+request.getServerName()
+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML
4.01 Transitional//EN">
<html>
<head>
<base hreff="<%=basePath%>">
<title></title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control"
content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords"
content="keyword1,keyword2,keyword3">
<meta http-equiv="description"
content="This is my page">
</head>
<body>
<h1>欢迎登录本系统,${userName }</h1>
</body>
</html>
