[2025 1학기 스프링 부트 스터디] 석준환 #4주차

-스프링 컨테이너에 빈은 저 형식으로 저장된다

빈 이름과 빈 객체(return 되는 객체)

 

-스프링 컨테이너에 4개의 bean이 생성 된다. 그리고 각각의 의존 관계를 주입한다(DI)

즉 빈을 생성하고 의존 관계를 주입하는 2 단계로 나눠진다

 

-스프링 컨테이너를 생성하고 설정(구성) 정보를 참고해서 스프링 빈도 등록하고, 의존관계를 설정

 

 

package hello.core.beanfind;

import hello.core.AppConfig;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class ApplicationContextInfoTest {

    AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);

    @Test
    @DisplayName("모든 빈 출력하기")
    void findAllBean() {
        String[] beanDefinitionNames = ac.getBeanDefinitionNames();
        for (String beanDefinitionName : beanDefinitionNames) {
            Object bean = ac.getBean(beanDefinitionName);
            System.out.println("name = " + beanDefinitionName + "object = " + bean);

        }
    }
    @Test
    @DisplayName("애플리케이션 빈 출력하기")
    void findApplicationBean() {
        String[] beanDefinitionNames = ac.getBeanDefinitionNames();
        for (String beanDefinitionName : beanDefinitionNames) {
            BeanDefinition beanDefinition = ac.getBeanDefinition(beanDefinitionName);

            //Role ROLE_APPLICATION: 직접 등록한 애플리케이션 빈
            //Role ROLE_INF RASTRUCTURE: 스프링이 내부에서 사용하는 빈
            if(beanDefinition.getRole() == BeanDefinition.ROLE_APPLICATION) {
                Object bean = ac.getBean(beanDefinitionName);
                System.out.println("name = " + beanDefinitionName + "object = " + bean);

            }

        }
    }
}

-모든 빈 출력하기

스프링 내부에서 사용하는 빈과 직접 등록한 애플리케이션 빈 모두를 조회한다

실행하면 스프링에 등록된 모든 빈 정보를 출력할 수 있다.

`ac.getBeanDefinitionNames()` : 스프링에 등록된 모든 빈 이름을 조회한다.

`ac.getBean()` : 빈 이름으로 빈 객체(인스턴스)를 조회한다 

 

-애플리케이션 빈 출력하기

스프링이 내부에서 사용하는 빈은 제외하고, 등록한 빈만 출력해보자.

스프링이 내부에서 사용하는 빈은 `getRole()`로 구분할 수 있다.

`ROLE_APPLICATION` : 일반적으로 사용자가 정의한 빈

`ROLE_INFRASTRUCTURE` : 스프링이 내부에서 사용하는 빈

 

package hello.core.beanfind;

import hello.core.AppConfig;
import hello.core.member.MemberService;
import hello.core.member.MemberServiceImpl;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import static org.junit.jupiter.api.Assertions.*;

public class ApplicationContextBasicFindTest {
    AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);

    @Test
    @DisplayName("빈 이름으로 조회")
    void findBeanByName() {
        MemberService memberService = ac.getBean("memberService", MemberService.class);
        assertInstanceOf(MemberServiceImpl.class, memberService);
    }
    @Test
    @DisplayName("이름 없이 타입으로만 조회")
    void findBeanByType() {
        MemberService memberService = ac.getBean(MemberService.class);
        assertInstanceOf(MemberServiceImpl.class, memberService);
    }

    @Test
    @DisplayName("구체 타입으로 조회")
    void findBeanByName2() {
        MemberService memberService = ac.getBean("memberService", MemberServiceImpl.class);
        assertInstanceOf(MemberServiceImpl.class, memberService);
        //좋은 코드 아님 역할에 의존해야함 역할에 의존해야 한다 구현에 의존하면 안됨
    }

    @Test
    @DisplayName("빈 이름으로 조회x")
    void findBeanByNameX() {
//        MemberService memberService = ac.getBean("xxxx", MemberService.class);
        assertThrows(NoSuchBeanDefinitionException.class,
                () -> ac.getBean("xxxx", MemberService.class) );

    }
}

빈을 조회하는 방법

1. 빈 이름으로 조회

2.이름 없이 타입으로만 조회

-만약 타입이 겹치면 에러 발생

-타입이 겹치는 경우 이름으로 구분하도록 설정해야 함 (다음 코드에서 예시 나옴)

3.구현체 타입으로 조회

-구현이 아닌 역할에 의존해야 좋은 코드이므로 좋은 접근은 아님

 

 

package hello.core.beanfind;

import hello.core.AppConfig;
import hello.core.discount.DiscountPolicy;
import hello.core.member.MemberRepository;
import hello.core.member.MemoryMemberRepository;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Map;

import static org.junit.jupiter.api.Assertions.*;

public class ApplicationContextSameBeanFindTest {
    AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(SameBeanConfig.class);

    @Test
    @DisplayName("타입으로 조회시 같은 타입이 둘 이상 있으면, 중복 오류가 발생한다")
    void findBeanByTypeDuplicate() {
//        MemberRepository bean = ac.getBean(MemberRepository.class);

        assertThrows(NoUniqueBeanDefinitionException.class,
                () -> ac.getBean(MemberRepository.class)
        );
    }
    @Test
    @DisplayName("타입으로 조회시 같은 타입이 둘 이상 있으면, 빈 이름을 지정하면 된다")
    void findBeanByName() {
        MemberRepository bean = ac.getBean("memberRepository1" ,MemberRepository.class);

        assertInstanceOf(MemberRepository.class, bean);
    }

    @Test
    @DisplayName("특정 타입으로 모두 조회하기")
    void findAllBeanByType() {
        Map<String, MemberRepository> beansOfType = ac.getBeansOfType(MemberRepository.class);
        for (String s : beansOfType.keySet()) {
            System.out.println("key = " + s + " value = " + beansOfType.get(s));
        }
        System.out.println("beansOfType = " + beansOfType);
        assertEquals(beansOfType.size(), 2);
    }


    @Configuration
    static class SameBeanConfig {

        @Bean
        public MemberRepository memberRepository1() {
            return new MemoryMemberRepository();
        }

        @Bean
        public MemberRepository memberRepository2() {
            return new MemoryMemberRepository();
        }
    }
}

 

findAllBeanByType() 실행결과

key = memberRepository1 value = hello.core.member.MemoryMemberRepository@528c868
key = memberRepository2 value = hello.core.member.MemoryMemberRepository@466276d8
beansOfType = {memberRepository1=hello.core.member.MemoryMemberRepository@528c868, memberRepository2=hello.core.member.MemoryMemberRepository@466276d8}

 

결국 타입이 겹치면 이름으로 구분하도록 설정해야 한다!

부모 타입으로 조회하면, 자식 타입도 함께 조회한다.

그래서 모든 자바 객체의 최고 부모인 `Object` 타입으로 조회하면, 모든 스프링 빈을 조회한다.

package hello.core.beanfind;

import hello.core.AppConfig;
import hello.core.discount.DiscountPolicy;
import hello.core.discount.FixDiscountPolicy;
import hello.core.discount.RateDiscountPolicy;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Map;

import static org.junit.jupiter.api.Assertions.*;

public class ApplicationContextExtendsFindTest {
    AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(TestConfig.class);

    @Test
    @DisplayName("부모 타입으로 조회시 자식이 둘 이상 잇으면 중복 오류가 발생한다")
    void findBeanByParentTypeDuplicate() {
//        DiscountPolicy bean = ac.getBean(DiscountPolicy.class);
        assertThrows(NoUniqueBeanDefinitionException.class,
                () -> ac.getBean(DiscountPolicy.class)
                );

    }
    @Test
    @DisplayName("부모 타입으로 조회시, 자식이 둘 이상 있으면 빈 이름을 지정하면 된다")
    void findBeanByParentTypeBeanName() {
        DiscountPolicy rateDiscountPolicy = ac.getBean("rateDiscountPolicy",DiscountPolicy.class);
        assertInstanceOf(RateDiscountPolicy.class, rateDiscountPolicy);
    }
    @Test
    @DisplayName("특정 하위 타입으로 조회")
    void findBeanBySubType() {
        RateDiscountPolicy rateDiscountPolicy = ac.getBean(RateDiscountPolicy.class);
        assertInstanceOf(RateDiscountPolicy.class, rateDiscountPolicy);
    }
    @Test
    @DisplayName("부모 타입으로 모두 조회하기")
    void findAllBeanByParentType() {
        Map<String, DiscountPolicy> beansOfType = ac.getBeansOfType(DiscountPolicy.class);
        assertEquals(beansOfType.size(), 2);
        for (String key : beansOfType.keySet()) {
            System.out.println("key = " + key + " value = " + beansOfType.get(key));

        }
    }

    @Test
    @DisplayName("부모 타입으로 모두 조회하기 - Object")
    void findAllBeanByObjectType() {
        Map<String, Object> beansOfType = ac.getBeansOfType(Object.class);
        for (String key : beansOfType.keySet()) {
            System.out.println("key = " + key + " value = " + beansOfType.get(key));

        }
    }

    @Configuration
    static class TestConfig{
        @Bean
        public DiscountPolicy rateDiscountPolicy() {
            return new RateDiscountPolicy();
        }
        @Bean
        public DiscountPolicy fixDiscountPolicy() {
            return new FixDiscountPolicy();
        }
    }
}

findAllBeanByParentType() 실행 결과

key = rateDiscountPolicy value = hello.core.discount.RateDiscountPolicy@2b76ff4e
key = fixDiscountPolicy value = hello.core.discount.FixDiscountPolicy@7a1234bf

즉 DiscountPolicy가 부모인 bean들이 모두 조회된다

 

findAllBeanByObjectType() 실행 결과

key = org.springframework.context.annotation.internalConfigurationAnnotationProcessor value = org.springframework.context.annotation.ConfigurationClassPostProcessor@545b995e
key = org.springframework.context.annotation.internalAutowiredAnnotationProcessor value = org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor@76a2ddf3
key = org.springframework.context.annotation.internalCommonAnnotationProcessor value = org.springframework.context.annotation.CommonAnnotationBeanPostProcessor@524f3b3a
key = org.springframework.context.event.internalEventListenerProcessor value = org.springframework.context.event.EventListenerMethodProcessor@41e68d87
key = org.springframework.context.event.internalEventListenerFactory value = org.springframework.context.event.DefaultEventListenerFactory@49ff7d8c
key = applicationContextExtendsFindTest.TestConfig value = hello.core.beanfind.ApplicationContextExtendsFindTest$TestConfig$$SpringCGLIB$$0@29526c05
key = rateDiscountPolicy value = hello.core.discount.RateDiscountPolicy@2ef14fe
key = fixDiscountPolicy value = hello.core.discount.FixDiscountPolicy@77102b91
....등등

 

Object로 조회를 하니 스프링에 있는 모든 빈을 조회하게 되었다.

 

BeanFactory와 ApplicationContext

BeanFactory

-스프링 컨테이너의 최상위 인터페이스다.

-스프링 빈을 관리하고 조회하는 역할을 담당한다.

-`getBean()` 을 제공한다.

-지금까지 우리가 사용했던 대부분의 기능은 BeanFactory가 제공하는 기능이다.

vs

ApplicationContext

-BeanFactory 기능을 모두 상속받아서 제공한다.

-빈을 관리하고 조회하는 기능은 물론이고, 많은 부가기능이 추가된 인터페이스이다.

부가 기능

-메시지소스를 활용한 국제화 기능

예를 들어서 한국에서 들어오면 한국어로, 영어권에서 들어오면 영어로 출력

-환경변수

로컬, 개발, 운영등을 구분해서 처리

-애플리케이션 이벤트

이벤트를 발행하고 구독하는 모델을 편리하게 지원

-편리한 리소스 조회

파일, 클래스패스, 외부 등에서 리소스를 편리하게 조회

 

ApplicationContext는 BeanFactory의 기능을 상속받는다.

ApplicationContext는 빈 관리기능 + 편리한 부가 기능을 제공한다.

BeanFactory를 직접 사용할 일은 거의 없다. 부가기능이 포함된 ApplicationContext를 사용한다.

BeanFactory나 ApplicationContext를 스프링 컨테이너라 한다.

 

 

 

다양한 설정 형식 지원 - 자바 코드, XML

 

package hello.core;

import hello.core.discount.DiscountPolicy;
import hello.core.discount.FixDiscountPolicy;
import hello.core.discount.RateDiscountPolicy;
import hello.core.member.MemberService;
import hello.core.member.MemberServiceImpl;
import hello.core.member.MemoryMemberRepository;
import hello.core.order.OrderService;
import 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(getMemberRepository());
    }
    @Bean
    public static MemoryMemberRepository getMemberRepository() {
        return new MemoryMemberRepository();
    }
    @Bean
    public OrderService orderService() {
        return new OrderServiceImpl(getMemberRepository(), getDiscountPolicy());
    }
    @Bean
    public static DiscountPolicy getDiscountPolicy() {
        return new RateDiscountPolicy();
    }

}

 

이건 기존의 configuration과 bean 코드이다 이 자바 코드 형식을 xml 형식으로 바꾸면 아래의 코드와 같아진다

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="memberService" class="hello.core.member.MemberServiceImpl">
        <constructor-arg name="memberRepository" ref="memberRepository"/>
    </bean>

    <bean id="memberRepository" class="hello.core.member.MemoryMemberRepository"/>

    <bean id="orderService" class="hello.core.order.OrderServiceImpl">
        <constructor-arg name="memberRepository" ref="memberRepository" />
        <constructor-arg name="discountPolicy" ref="discountPolicy"/>
    </bean>

    <bean id="discountPolicy" class="hello.core.discount.RateDiscountPolicy" />

</beans>

똑같이 총 4개의 빈이 등록되었고 빈의 구성도 같다

 

스프링 빈 설정 메타 정보 - BeanDefinition

스프링 컨테이너는 BeanDefinition(역할)에만 의존한다

-XML을 읽어서 BeanDefinition을 만들면 된다.

-자바 코드를 읽어서 BeanDefinition을 만들면 된다.

-->스프링 컨테이너는 자바 코드인지, XML인지 몰라도 된다. 오직 BeanDefinition만 알면 된다.

 

-AnnotationConfigApplicationContext` 는 `AnnotatedBeanDefinitionReader` 를 사용해서

`AppConfig.class` 를 읽고 `BeanDefinition` 을 생성한다.

-`GenericXmlApplicationContext` 는 `XmlBeanDefinitionReader` 를 사용해서 `appConfig.xml`

설정 정보를 읽고 `BeanDefinition` 을 생성한다.

-새로운 형식의 설정 정보가 추가되면, XxxBeanDefinitionReader를 만들어서 `BeanDefinition` 을 생성하

면 된다.

 

package hello.core.beandefinition;

import hello.core.AppConfig;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class BeanDefinitionTest {

    AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);

    @Test
    @DisplayName("빈 설정 메타정보 확인")
    void findApplicationBean() {
        String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
        for (String beanDefinitionName : beanDefinitionNames) {
            BeanDefinition beanDefinition = applicationContext.getBeanDefinition(beanDefinitionName);
            
            if(beanDefinition.getRole() == BeanDefinition.ROLE_APPLICATION) {
                System.out.println("beanDefinitionName = " + beanDefinitionName +
                        " beanDefinition = " + beanDefinition);
            }
        }
    }
    
}

 

실행 결과

beanDefinitionName = appConfig beanDefinition = Generic bean: class=hello.core.AppConfig$$SpringCGLIB$$0; scope=singleton; abstract=false; lazyInit=null; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; fallback=false; factoryBeanName=null; factoryMethodName=null; initMethodNames=null; destroyMethodNames=null
beanDefinitionName = memberService beanDefinition = Root bean: class=null; scope=; abstract=false; lazyInit=null; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; fallback=false; factoryBeanName=appConfig; factoryMethodName=memberService; initMethodNames=null; destroyMethodNames=[(inferred)]; defined in hello.core.AppConfig
beanDefinitionName = getMemberRepository beanDefinition = Root bean: class=hello.core.AppConfig; scope=; abstract=false; lazyInit=null; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; fallback=false; factoryBeanName=null; factoryMethodName=getMemberRepository; initMethodNames=null; destroyMethodNames=[(inferred)]; defined in hello.core.AppConfig
beanDefinitionName = orderService beanDefinition = Root bean: class=null; scope=; abstract=false; lazyInit=null; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; fallback=false; factoryBeanName=appConfig; factoryMethodName=orderService; initMethodNames=null; destroyMethodNames=[(inferred)]; defined in hello.core.AppConfig
beanDefinitionName = getDiscountPolicy beanDefinition = Root bean: class=hello.core.AppConfig; scope=; abstract=false; lazyInit=null; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; fallback=false; factoryBeanName=null; factoryMethodName=getDiscountPolicy; initMethodNames=null; destroyMethodNames=[(inferred)]; defined in hello.core.AppConfig

 

BeanClassName: 생성할 빈의 클래스 명(자바 설정 처럼 팩토리 역할의 빈을 사용하면 없음)

factoryBeanName: 팩토리 역할의 빈을 사용할 경우 이름, 예) appConfig

factoryMethodName: 빈을 생성할 팩토리 메서드 지정, 예) memberService

Scope: 싱글톤(기본값)

lazyInit: 스프링 컨테이너를 생성할 때 빈을 생성하는 것이 아니라, 실제 빈을 사용할 때 까지 최대한 생성을 지연

처리 하는지 여부

InitMethodName: 빈을 생성하고, 의존관계를 적용한 뒤에 호출되는 초기화 메서드 명

DestroyMethodName: 빈의 생명주기가 끝나서 제거하기 직전에 호출되는 메서드 명

Constructor arguments, Properties: 의존관계 주입에서 사용한다. (자바 설정 처럼 팩토리 역할의 빈을 사용

하면 없음)

 

 

스프링이 다양한 형태의 설정 정보를 BeanDefinition으로 추상화해서 사용한다는 것이 핵심