<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>5.3.9</version>
</dependency>

package com.meimeixia.dao;

/**
 * 數(shù)據(jù)訪(fǎng)問(wèn)層接口
 * @author liayun
 * @create 2021-09-19 18:17
 */
public interface UserDao {

    public void add();

}

package com.meimeixia.dao.impl;

import com.meimeixia.dao.UserDao;

/**
 * 數(shù)據(jù)訪(fǎng)問(wèn)層實(shí)現(xiàn)類(lèi)
 * @author liayun
 * @create 2021-09-19 18:29
 */
public class UserDaoImpl implements UserDao {

    @Override
    public void add() {
        System.out.println("UserDao...");
    }

}

package com.meimeixia.service;

/**
 * 業(yè)務(wù)邏輯層接口
 * @author liayun
 * @create 2021-09-19 18:31
 */
public interface UserService {

    public void add();

}

package com.meimeixia.service.impl;

import com.meimeixia.dao.UserDao;
import com.meimeixia.service.UserService;

/**
 * 業(yè)務(wù)邏輯層實(shí)現(xiàn)類(lèi)
 * @author liayun
 * @create 2021-09-19 18:37
 */
public class UserServiceImpl implements UserService {

    // 因?yàn)闃I(yè)務(wù)邏輯層是要調(diào)用數(shù)據(jù)訪(fǎng)問(wèn)層中的功能的，所以在這兒我們得聲明一個(gè)UserDao類(lèi)型的變量
    private UserDao userDao; // 注意了，這兒我們并沒(méi)有為該變量進(jìn)行賦值，賦值的操作得交給Spring去做，只是這樣做的前提是我們得為該變量提供一個(gè)setter方法

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public void add() {
        System.out.println("UserService...");
        userDao.add();
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="userDao" class="com.meimeixia.dao.impl.UserDaoImpl"></bean>

    <bean id="userService" class="com.meimeixia.service.impl.UserServiceImpl">
        <property name="userDao" ref="userDao"></property>
    </bean>

</beans>

package com.meimeixia.controller;

import com.meimeixia.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author liayun
 * @create 2021-09-19 18:41
 */
public class UserController {
    public static void main(String[] args) throws Exception {
        // 1. 創(chuàng)建Spring的容器對(duì)象
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        // 2. 從容器對(duì)象中獲取UserService對(duì)象
        UserService userService = applicationContext.getBean("userService", UserService.class);
        // 3. 調(diào)用UserService對(duì)象的方法進(jìn)行業(yè)務(wù)邏輯處理
        userService.add();
    }
}