Spring中的依赖注入DI详解

<bean name ="orderService" class ="com.zzy.service.OrderService">          
</bean>

<bean name ="userService" class ="com.zzy.service.UserService">
    <property name="orderService" ref= "orderService"></property>     
</bean>

<bean name ="orderService" class ="com.zzy.service.OrderService">          
</bean>

<bean name ="userService" class ="com.zzy.service.UserService">
    <constructor-arg index="0" ref= "orderService"/>     
</bean>

<bean name ="orderService" class ="com.zzy.service.OrderService">          
</bean>
<!--autowire  默认五种方式(ByType,ByName,default,no,constructor),
byType:根据类型去容器寻找
ByName:找set方法,去除Set后的名称去容器中寻找
no:默认
-->
<bean name ="userService" class ="com.zzy.service.UserService" autowire = "byType"> 
</bean>

package com.zzy.zzyNotes.spring.DI依赖注入;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
/**
 * @author: zzy
 * @createDate: 2022-01-07 15:28
 * @description:
 * spring依赖注入的方式
 * 1.属性注入
 * 2.方法注入
 * 3.构造器注入
 *  @Autowired  先根据Type,在根据名字注入,可以放在属性.普通方法,构造方法上
 *
 *  @Resource  根据名字注入,可以放在属性.普通方法上
 *
 *  @Qualifier  指定注入Bean的名字,可以放在属性.普通方法(单参数),普通方法形参前,构造方法形参前
 *
 *  @Primary  相同类型的Bean的优先级最高
 */
@Service
public class UserService {
    //一:属性注入 -------------------------------------------------------------------------------------------------------
    //接口
    @Autowired                         //@Autowired先根据Type,在根据名字
    @Qualifier("ticketsOrderService")  //指定寻找的名字
    private OrderService orderService;
    //类
    @Autowired                         //@Autowired先根据Type,在根据名字
    private GoodsOrderService goodsOrderService;
    //二:方法注入不一定是set方法) -----------------------------------------------------------------------------------------
    //使用方法注入
    //这个我们想指定注入水果Bean
    //方式有三种
    //1.@Primary FruitsOrderService上加@Primary
    //2.@Autowired 配合 @Qualifier("fruitsOrderService") @Qualifier可以加在参数前面
    //2.@Resource(name = "fruitsOrderService") 根据name注入
    private OrderService fruitsOrderService;
    private OrderService goodsOrderService2;
    @Autowired
    //@Resource(name = "fruitsOrderService")
    public void fruits(OrderService orderService,GoodsOrderService goodsOrderService) {
        this.fruitsOrderService = orderService;
        this.goodsOrderService2 = goodsOrderService;
    }
    //三:构造方法注入            -----------------------------------------------------------------------------------------
    //构造方法注入meatOrderService,啥也不加会注入fruitsOrderService,因为@Primary.需要用@Qualifier("meatOrderService")指定
    private OrderService meatOrderService;
    @Autowired
    public UserService( OrderService orderService) {
        this.meatOrderService = orderService;
    }
    public UserService() {
    }
    /**
     * 查询注入的Bean
     */
    public void getBean() {
        System.out.println(orderService);
        System.out.println("属性注入 --------");
        System.out.println(goodsOrderService);
        System.out.println("属性注入 --------");
        System.out.println(fruitsOrderService);
        System.out.println("方法注入 --------");
        System.out.println(goodsOrderService2);
        System.out.println("方法注入 --------");
        System.out.println(meatOrderService);
        System.out.println("构造器注入 --------");
    }
}