package interface_package;

public interface Animal {
    public void Bigger(String  name);
}

package class_package;

import interface_package.Animal;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class Dog implements Animal {
    private String name;
    private Mouse Cat;

    public Mouse getCat() {
        return Cat;
    }

    @Autowired
    public void setCat(Mouse cat) {
        Cat = cat;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public void Bigger(String name){
        System.out.println("I am " +   getName() + "  bigger than " + getCat().getName()  +  ", hi~");
    }
}
 

package class_package;

import interface_package.Animal;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class Cat implements Animal {

    private String name;
    private Mouse mouse1;


    public Mouse getMouse1() {
        return mouse1;
    }
    @Autowired
    public void setMouse1(Mouse mouse) {
        this.mouse1 = mouse;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public void Bigger(String name){
        System.out.println("I am " +   getName() + "  bigger than " + mouse1.getName()  +  ", hi~");
    }
}
 

package class_package;

import interface_package.Animal;

public class Mouse implements Animal {

    private String name;
    private Mouse mouse;

    public Mouse getMouse() {
        return mouse;
    }

    public void setMouse(Mouse mouse) {
        this.mouse = mouse;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public void Bigger(String name){
        System.out.println("I am " + getName()  + ", hi~");
    }

}
 

測試類

package test_package;


import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringTest {
    public static void main(String []args){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
    }
}

<?xml version="1.0" encoding="GBK"?>
<!--要使用註解的話，就要先引入對應的配置-->
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context-4.0.xsd">

    <context:component-scan base-package=" class_package"/>

</beans>

這裡寫的是spring5新加入的註解。

1. 當標註使用自動裝配註解，而容器中沒有符合條件的bean的時候，Autowired的處理方式和aitowire=“ByType”不一樣，AutoWire會直接報錯，為了讓Autowire可以和aitowire=“ByType”一樣只是不執行任何步驟，可以將Autowire的引數required設定為fanse，當然，也可以使用spring5新加入的註解[email protected]

   //    這裡，當將required設定為false的時候，如果spring找不到符合條件的時候，也不會報錯。
       @Autowired(required = false)
       public void setCat(Mouse cat) {
           Cat = cat;
       }
   

   在用IDEA做實驗的時候發現IDEA只有spring4的，所以我找了個5的在這。

   package class_package;
   
   import interface_package.Animal;
   
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.beans.factory.annotation.Required;
   import org.springframework.beans.factory.annotation.Value;
   import org.springframework.lang.Nullable;
   import org.springframework.stereotype.Component;
   
   @Component
   public class Dog implements Animal {
       @Value("dog")
       private String name;
       private Cat Cat;
   
       public Cat getCat() {
           return Cat;
       }
   
   //    這裡，當將required設定為false的時候，如果spring找不到符合條件的時候，也不會報錯。
       @Autowired(required = false)
       public void setCat(Cat cat) {
           Cat = cat;
       }
   
   
   
       @Override
       public void Bigger(String name){
           System.out.println("I am " +   name + "  bigger than " + getCat().getName()  +  ", hi~");
       }
   }