[Spring 핵심 원리 - 기본편] @Configuration과 싱글톤

@Configuration과 싱글톤

그런데 이상한 점이 있다. 코드를 보자

 

public class AppConfig {

    //@Bean memberService -> new MemoryMemberRepository()
    //@Bean orderSErvice -> new MemoryMemberRepository()
    @Bean
    public MemberService memberService() {
        return new MemberServiceImpl(memberRepository());
    }

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

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

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

• memberService 빈을 만드는 코드를 보면 'memberRepository()'를 호출한다.
  • 이 메서드를 호출하면 'new MemoryMemberRepository()'를 호출한다.
• orderService 빈을 만드는 코드도 동일하게 'memberRepository()'를 호출한다.
  • 이 메서드를 호출하면 'new MemoryMemberRepository()'를 호출한다.

결과적으로 각각 다른 2개의 'MemoryMemberRepository'가 생성되면서 싱글톤이 깨지는 것 처럼 보인다. 스프링 컨테이너는 이 문제를 어떻게 해결할까?

 

직접 테스트 해보자.

 

public class AppConfig {

    //@Bean memberService -> new MemoryMemberRepository()
    //@Bean orderSErvice -> new MemoryMemberRepository()

    //call AppConfig.memberService
    //call AppConfig.memberRepository
    //call AppConfig.memberRepository
    //call AppConfig.orderService
    //call AppConfig.memberRepository

    //call AppConfig.memberService
    //call AppConfig.memberRepository
    //call AppConfig.orderService
    @Bean
    public MemberService memberService() {
        System.out.println("call AppConfig.memberService");
        return new MemberServiceImpl(memberRepository());
    }

    @Bean
    public OrderService orderService() {
        System.out.println("call AppConfig.orderService");
        return new OrderServiceImpl(
                memberRepository(),
                discountPolicy());
    }

    @Bean
    public MemberRepository memberRepository() {
        System.out.println("call AppConfig.memberRepository");
        return new MemoryMemberRepository();
    }

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

 

 

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

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