springboot从分层到解耦

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 {@Overridepublic 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();@Overridepublic 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;}@Overridepublic 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