애노테이션 @PostConstruct, @PreDestroy

NetworkClient

package inflearn.spring_core.lifecycle;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

public class NetworkClient { // implement 지움

    private String url;

    public NetworkClient() {
        System.out.println("생성자 호출, url = " + url);
    }

    public void setUrl(String url) {
        this.url = url;
    }

    //서비스 시작시 호출
    public void connect() {
        System.out.println("connect: " + url);
    }

    public void call(String message) {
        System.out.println("call: " + url + " message = " + message);
    }

    //서비스 종료시 호출
    public void disConnect() {
        System.out.println("close + " + url);
    }


    @PostConstruct
    public void init() {
        System.out.println("NetworkClient.init");
        connect();
        call("초기화 연결 메시지");
    }

    @PreDestroy
    public void close() {
        System.out.println("NetworkClient.close");
        disConnect();
    }
}

 

BeanLifecycleTest

package inflearn.spring_core.lifecycle;

import org.junit.jupiter.api.Test;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

public class BeanLifeCycleTest {

    @Test
    public void lifeCycleTest() {
        ConfigurableApplicationContext ac = new AnnotationConfigApplicationContext(LifeCycleConfig.class);
        NetworkClient client = ac.getBean(NetworkClient.class);
        ac.close(); //스프링 컨테이너를 종료, ConfigurableApplicationContext 필요
    }


    // static 클래스
    @Configuration
    static class LifeCycleConfig {

        @Bean
        public NetworkClient networkClient() {
            NetworkClient networkClient = new NetworkClient();
            networkClient.setUrl("http://hello-spring.dev");
            return networkClient;
        }
    }
}

 

 

실행 결과

생성자 호출, url = null
NetworkClient.init
connect: http://hello-spring.dev
call: http://hello-spring.dev message = 초기화 연결 메시지
20:49:04.729 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@43dac38f, started on Wed Oct 11 20:49:04 KST 2023
NetworkClient.close
close + http://hello-spring.dev

Process finished with exit code 0

• @PostConstruct , @PreDestroy 이 두 애노테이션을 사용하면 가장 편리하게 초기화와 종료를 실행할 수 있다.

 

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정리

# @PostConstruct, @PreDestroy 애노테이션을 사용하자

# 코드를 고칠 수 없는 외부 라이브러리를 초기화, 종료해야 하면 @Bean 의 initMethod, destroyMethod 를 사용하자.