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Java实战之实现用户登录

作者：龙崎流河　　发布时间：2022-08-03 14:42:55　

标签：Java,用户登录

一、前言

二、案例需求

1.编写login.html登录页面，username&password两个输入框

2.使用Druid数据库连接池技术，操作mysql，day14数据库中的user表

3.使用jdbcTemplate技术封装JDBC

4.登录成功跳转到SuccessServlet展示：登录成功！用户名，欢迎你

5.登录失败跳转到FailServlet展示：登录失败密码错误

三、开始第一步

首先创建项目，写html页面，配置文件，jar包

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="/day14/loginServlet" method="post">
用户名:<input type="text" name="username"> <br>
密码：<input type="password" name="password"> <br>
<input type="submit" value="登录">
</form>
</body>
</html>

druid.properties配置文件：

driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql:///day14
username=root
password=root
#初始化连接数量
initialSize=5
#最大连接数
maxActive=10
#最大等待时间
maxWait=3000
filters=stat
timeBetweenEvictionRunsMillis=60000
minEvictableIdleTimeMillis=300000
validationQuery=SELECT 1
testWhileIdle=true
testOnBorrow=false
testOnReturn=false
poolPreparedStatements=false
maxPoolPreparedStatementPerConnectionSize=200

导入jar包：

四、第二步

创建user类：

package com.wzc.domain;
//用户的实体类
public class User {
private int id;
private String username;
private String password;
public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}

五、第三步

创建jdbcUtils工具类

package com.wzc.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

//JDBC工具类使用Druid连接池
public class JDBCUtils {
private static DataSource ds ;
static {
try {
// 加载配置文件
Properties pro = new Properties();
// 使用ClassLoader加载配置文件，获取字节输入流
InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
pro.load(is);
// 初始化连接池对象
ds = DruidDataSourceFactory.createDataSource(pro);
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
// 初始化连接池
}
/*获取连接池对象*/
public static DataSource getDataSource(){
return ds;
}
/*获取连接connection对象*/
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}

}

创建UserDao类，提供login方法：

package com.wzc.dao;

import com.wzc.domain.User;
import com.wzc.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

//操作数据库中user表的类
public class UserDao {
// 声明JDBCTemplate对象共用
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

/**
* 登录方法
* @param loginUser 只有用户名和密码
* @return user包含用户全部数据,没有查询到则返回null
*/
public User login(User loginUser){
try{
// 编写sql
String sql = "select * from user where username = ? and password = ?";
// 调用query方法
User user = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class),
loginUser.getUsername(), loginUser.getPassword());
return user;
} catch (DataAccessException e){
e.printStackTrace();
// 记录日志
return null;
}
}

}

编写loginServlet类：

package com.wzc.web.servlet;

import com.wzc.dao.UserDao;
import com.wzc.domain.User;
import org.apache.commons.beanutils.BeanUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 设置编码
req.setCharacterEncoding("utf-8");
/*// 获取请求参数
String username = req.getParameter("username");
String password = req.getParameter("password");
// 封装user对象
User loginUser = new User();
loginUser.setUsername(username);
loginUser.setPassword(password);*/
// 获取所有请求参数
Map<String,String[]> map = req.getParameterMap();
// 创建User对象
User loginUser = new User();
// 使用BeanUtils封装
try {
BeanUtils.populate(loginUser,map);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
// 调用UserDao的login方法
UserDao dao = new UserDao();
User user = dao.login(loginUser);
// 判断user
if (user == null){
// 登录失败
req.getRequestDispatcher("/failServlet").forward(req,resp);
}else{
// 登录成功
// 存储数据
req.setAttribute("user",user);
// 转发
req.getRequestDispatcher("/successServlet").forward(req,resp);
}
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}

六、第四步

编写SuccessServlet类：

package com.wzc.web.servlet;

import com.wzc.domain.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "/successServlet")
public class SuccessServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 获取request域中共享的user对象
User user = (User)request.getAttribute("user");
if (user !=null){
//给页面写一句话
// 设置编码
response.setContentType("text/html;charset=utf-8");
// 输出
response.getWriter().write("登录成功!"+user.getUsername()+",欢迎你");
}
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}

编写FailServelt类

package com.wzc.web.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//给页面写一句话
// 设置编码
response.setContentType("text/html;charset=utf-8");
// 输出
response.getWriter().write("登录失败，用户名和密码错误");
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}

输入错误的账号和密码

登录失败提示：

七、总结

**BeanUtils工具类，简化数据封装：**用于封装javaBean

javaBean：标准的java类功能：封装数据

有一下四点要求：

1.类必须被public修饰

2.必须提供空参的构造器

3.成员变量必须使用private修饰

4.提供公共setter和getter方法

属性：setter和getter方法截取后的产物
例如：getUsername()–>Username–>username
可见username就是属性
方法有三种：

1.setProperty()
2.getProperty()
3.populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中（最常用）

package com.wzc.test;

import com.wzc.domain.User;
import org.apache.commons.beanutils.BeanUtils;
import org.junit.Test;

import java.lang.reflect.InvocationTargetException;

public class BeanUtilsTest {
@Test
public void test(){
User user = new User();
try {
BeanUtils.setProperty(user,"hehe","male");
System.out.println(user);
String gender = BeanUtils.getProperty(user, "hehe");
System.out.println(gender);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
}
}

来源：https://blog.csdn.net/Jiaodaqiaobiluo/article/details/116147939

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