依赖

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

AOP

 

IOC理论推导 控制反转，主动权交给用户

1.dao层是用来实现业务，和数据库打交道

dao层 接口

package com.tengxian.dao;

public interface UserDao {
    void getUser();
}

dao接口的实现1，默认获取

package com.tengxian.dao;

public class UserDaoImpl implements UserDao{
    @Override
    public void getUser() {
        System.out.println("默认获取用户是数据");
    }
}

dao接口的实现类2，mysql获取

package com.tengxian.dao;

public class UserDaoMysqlImpl implements UserDao{
    @Override
    public void getUser() {
        System.out.println("Mysql 获取数据！");
    }
}

 

service层，

服务层接口

package com.tengxian.service;

public interface  UserService {
    void getUser();
}

服务处实现类

package com.tengxian.service;

import com.tengxian.dao.UserDao;
import com.tengxian.dao.UserDaoImpl;

public class UserServiceImpl implements UserService{

    //业务层调用Dao层
    private UserDao userDao;

    //利用set进行动态实现值的注入
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public void getUser() {
        userDao.getUser();
    }
}

用户层：用户实际要用的是业务层，dao层他们不用接触

import com.tengxian.dao.UserDaoImpl;
import com.tengxian.dao.UserDaoMysqlImpl;
import com.tengxian.service.UserServiceImpl;

public class MyTest {
    public static void main(String[] args) {
        //用户实际要用的是业务层，dao层他们不用接触
        UserServiceImpl userService = new UserServiceImpl();
        userService.setUserDao(new UserDaoImpl());

        userService.getUser();
    }
}