注释很详细，直接上代码

三层架构

• 项目结构
  

源码：

HelloController

package com.amoorzheyu.controller;

import com.amoorzheyu.pojo.User;
import com.amoorzheyu.service.HelloService;
import com.amoorzheyu.service.impl.HelloServiceA;
import org.springframework.format.annotation.DateTimeFormat;
import org.springframework.web.bind.annotation.*;

import java.time.LocalDateTime;
import java.util.Arrays;
import java.util.List;

/*  注解标识请求处理类 */
@RestController
public class HelloController {

    private HelloService helloService = new HelloServiceA();
    /* 标识请求路径 */
    //test
    @RequestMapping( "/hello")
    public String hello(){
        List<User> list =helloService.getUserList() ;
        return list.toString();
    }
}

HelloDao

package com.amoorzheyu.dao;

import com.amoorzheyu.pojo.User;

import java.util.List;

public interface HelloDao {
    //获取用户信息列表
    public List<User> getUserList();
}

HelloDaoA

package com.amoorzheyu.dao.impl;

import com.amoorzheyu.dao.HelloDao;
import com.amoorzheyu.pojo.User;

import java.util.ArrayList;
import java.util.List;

public class HelloDaoA implements HelloDao {

    @Override
    public List<User> getUserList() {

        //调用dao获取数据
        List<User> ReturnList = new ArrayList<User>();

        //模拟数据
        ReturnList.add(new User("Amoor", 18,null));
        ReturnList.add(new User("Bob", 19,null));
        ReturnList.add(new User("Candy", 20,null));
        return ReturnList;
    }
}

HelloService

package com.amoorzheyu.service;

import com.amoorzheyu.pojo.User;

import java.util.List;

public interface HelloService {
    //获取信息列表
    public List<User> getUserList();
}

HelloServiceA

package com.amoorzheyu.service.impl;

import com.amoorzheyu.dao.HelloDao;
import com.amoorzheyu.dao.impl.HelloDaoA;
import com.amoorzheyu.pojo.User;
import com.amoorzheyu.service.HelloService;

import java.util.List;

public class HelloServiceA implements HelloService {

    //newDao实现类
    private HelloDao helloDao = new HelloDaoA();


    @Override
    public List<User> getUserList() {

        List<User> ReturnList = helloDao.getUserList();

        return ReturnList;
    }
}

User

package com.amoorzheyu.pojo;

public class User {
    private Integer age;
    private String name;

    private Address address;

    public User( String name,Integer age, Address address) {
        this.age = age;
        this.name = name;
        this.address = address;
    }

    public Address getAddres() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "age=" + age +
                ", name='" + name + '\'' +
                ", address=" + address +
                '}';
    }
}

我们可以发现层级之间在new时耦合了，也就是说改了此处会影响其他地方，其他位置也需要改动，为了解决这些问题我们可以引入以下思想

控制反转：Inversion Of Control，简称ioc，对象的创建控制权由程序自身转移到外部（容器），这种思想称为控制反转；
依赖注入：Dependency Injection，简称Dl,容器为应用程序提供运行时，所依赖的资源，称之为依赖注入；
Bean对象：Oc容器中创建、管理的对象，称之为bean；

解耦

以下修改为去除new的内容+添加控制反转与依赖注入注解