Java实战之实现用户登录

Java实战之实现用户登录

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

用户名:

密码：

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connecthttp://ion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.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 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http://、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

login.html中form表单的action路径写法：虚拟路径+Servlet的资源路径

**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();

}

}

}

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