[Spring] Component Scan을 통한 의존관계 설정

HelloSpringApplication.class

package hello.hellospring;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class HelloSpringApplication {

	public static void main(String[] args) {
		SpringApplication.run(HelloSpringApplication.class, args);
	}

}

 

controller.MemberController.class

package hello.hellospring.controller;

import hello.hellospring.service.MemberService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

@Controller
public class MemberController {

    private final MemberService memberService;

    @Autowired
    public MemberController(MemberService memberService) {
        this.memberService = memberService;
    }
}

 

 

 

MemberService.class

 

package hello.hellospring.service;

import hello.hellospring.domain.Member;
import hello.hellospring.repository.MemberRepository;
import hello.hellospring.repository.MemoryMemberRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class MemberService {

    private final MemberRepository  memberRepository;

    //MemberService입장에서 외부repository를 넣어줌 - > Dependency Injection!
    @Autowired
    public MemberService(MemberRepository memberRepository){
        this.memberRepository = memberRepository;
    }

    //회원가입

    public Long join(Member member){
        //같은 있는 중복 회원X
        validateDuplicateMember(member);

        memberRepository.save(member);
        return member.getId();
    }

    private void validateDuplicateMember(Member member) {
        memberRepository.findByName(member.getName())
                        .ifPresent(m -> {
                            throw new IllegalStateException("이미 존재하는 회원입니다.");
                        });
    }

    public List<Member> findMembers(){
        return memberRepository.findAll();
    }

    public Optional<Member> findOne(Long memberId){
        return memberRepository.findById(memberId);
    }


}

 

 

 

 

MemoryMemberRepository.class

package hello.hellospring.repository;
import hello.hellospring.domain.Member;
import org.springframework.stereotype.Repository;

import java.util.*;



@Repository
public class MemoryMemberRepository implements MemberRepository{
    private static Map<Long, Member> store = new HashMap<>();
    private static long sequence = 0L;

    @Override
    public Member save(Member member) {
        member.setId(++sequence);
        store.put(member.getId(), member);
        return member;
    }

    @Override
    public Optional<Member> findById(Long id) {
        return Optional.ofNullable(store.get(id));
    }

    @Override
    public Optional<Member> findByName(String name) {
        return store.values().stream()
                .filter(member-> member.getName().equals(name))
                .findAny();
    }

    @Override
    public List<Member> findAll() {
        return new ArrayList<>(store.values());
    }



    public void clearStore(){
        store.clear();
    }
}

 

 

@Component annotation을 통해

MemberController -> MemberService -> MemoryMemberRepository 순으로

의존관계를 주입하고 있다.

 

 

 

cf.

/*
 * Copyright 2002-2022 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.stereotype;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.core.annotation.AliasFor;

/**
 * Indicates that an annotated class is a "Repository", originally defined by
 * Domain-Driven Design (Evans, 2003) as "a mechanism for encapsulating storage,
 * retrieval, and search behavior which emulates a collection of objects".
 *
 * <p>Teams implementing traditional Java EE patterns such as "Data Access Object"
 * may also apply this stereotype to DAO classes, though care should be taken to
 * understand the distinction between Data Access Object and DDD-style repositories
 * before doing so. This annotation is a general-purpose stereotype and individual teams
 * may narrow their semantics and use as appropriate.
 *
 * <p>A class thus annotated is eligible for Spring
 * {@link org.springframework.dao.DataAccessException DataAccessException} translation
 * when used in conjunction with a {@link
 * org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor
 * PersistenceExceptionTranslationPostProcessor}. The annotated class is also clarified as
 * to its role in the overall application architecture for the purpose of tooling,
 * aspects, etc.
 *
 * <p>As of Spring 2.5, this annotation also serves as a specialization of
 * {@link Component @Component}, allowing for implementation classes to be autodetected
 * through classpath scanning.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 2.0
 * @see Component
 * @see Service
 * @see org.springframework.dao.DataAccessException
 * @see org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Repository {

	/**
	 * The value may indicate a suggestion for a logical component name,
	 * to be turned into a Spring bean in case of an autodetected component.
	 * @return the suggested component name, if any (or empty String otherwise)
	 */
	@AliasFor(annotation = Component.class)
	String value() default "";

}

 

@Controller, @Service, @Repository 내부에

@Component가 포함되어 있다.