[섹션 5] @Configuation과 싱글톤

본 게시물은 김영한 선생님의 강의를 학습하며 작성하였습니다.

@Configuation은 singleton을 위해 존재!!

package com.hello.core.singleton;

import com.hello.core.AppConfig;
import com.hello.core.member.MemberRepository;
import com.hello.core.member.MemberServiceImpl;
import com.hello.core.order.OrderServiceImpl;
import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class ConfigurationSingletonTest {
    @Test
    void configurationTest() {
        AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);

        MemberServiceImpl memberService = ac.getBean("memberService", MemberServiceImpl.class);
        OrderServiceImpl orderService = ac.getBean("orderService", OrderServiceImpl.class);
        MemberRepository memberRepository = ac.getBean("memberRepository", MemberRepository.class);

        MemberRepository memberRepository1 = memberService.getMemberRepository();
        MemberRepository memberRepository2 = orderService.getMemberRepository();

        System.out.println("memberRepository = " + memberRepository);
        System.out.println("memberService -> memberRepository1 = " + memberRepository1);
        System.out.println("orderService -> memberRepository2 = " + memberRepository2);

        Assertions.assertThat(memberService.getMemberRepository()).isSameAs(memberRepository);
        Assertions.assertThat(orderService.getMemberRepository()).isSameAs(memberRepository);
    }
}

package com.hello.core;

import com.hello.core.discount.DiscountPolicy;
import com.hello.core.discount.RateDiscountPolicy;
import com.hello.core.member.MemberRepository;
import com.hello.core.member.MemberService;
import com.hello.core.member.MemberServiceImpl;
import com.hello.core.member.MemoryMemberRepository;
import com.hello.core.order.OrderService;
import com.hello.core.order.OrderServiceImpl;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class AppConfig {
    @Bean
    public MemberService memberService() {
        return new MemberServiceImpl(memberRepository());
    }

    @Bean
    public MemberRepository memberRepository() {
        return new MemoryMemberRepository();
    }

    @Bean
    public OrderService orderService() {
        return new OrderServiceImpl(memberRepository(), discountPolicy());
    }

    @Bean
    public DiscountPolicy discountPolicy() {
        return new RateDiscountPolicy();
    }
}

왜 3개 다 똑같을까?

로직은 3번 실행되어야 맞는거같은데

@Configuation과 바이트코드의 조작의 마법