SpringBoot容器初始化/卸載資源的幾種姿勢

日常開發中長需要在Bean初始化過程中加載一些資源或者是在Bean銷燬前釋放一些資源，Spring提供了多種不同的方式初始化和銷燬Bean。這裏我收集了幾個分享給進來的朋友們!

> 1. initMethod / destroyMethod

@Configuration
public class InitializeOne {
	
	@Bean(initMethod = "init", destroyMethod = "destroy")
	 public HelloService hello() {
		
		return new HelloService();
	 }
}

HelloService.java

public class HelloService {
	
	public void init() {
		System.out.println("this is init......");
	}
	
	public void destroy() {
		System.out.println("this is destroy......");
	}

}

> 2. InitializingBean (初始化)、DisposableBean (銷燬)

@Configuration
public class initializeTwo implements InitializingBean, DisposableBean{

	@Override
	public void afterPropertiesSet() throws Exception {
		// TODO Auto-generated method stub
		System.out.println("this is InitializingBean 的 init......");
	}

	@Override
	public void destroy() throws Exception {
		// TODO Auto-generated method stub
		System.out.println("this is DisposableBean 的 destory......");
	}

}

> 3. @PostConstruct (初始化)、 @PreDestroy(銷燬)

注：這兩個不是spring的註解

@Configuration
public class initializeThree {
	
	@PostConstruct
	public void init() {
		System.out.println("@PostConstruct 的 init......");
	}
	
	@PreDestroy
	public void preDestory() {
		System.out.println("@PreDestroy 的 preDestory......");
	}

}

> 4. ContextStartedEvent (初始化)、ContextClosedEvent (銷燬)

說明：這種方式使用 Spring 事件機制,Spring 啓動之後調用ApplicationContext.start() 方法將會發送 ContextStartedEvent 事件，調用ApplicationContext.close()將會發送 ContextClosedEvent事件，這種方式會相對麻煩一些，如果不想用這種方式可以修改爲第5中方法。

@Configuration
public class initializeFour implements ApplicationListener{

	@Override
	public void onApplicationEvent(ApplicationEvent event) {
		// TODO Auto-generated method stub
		if(event instanceof ContextStartedEvent) {
			System.out.println("this is ContextStartedEvent ......");
		}else if(event instanceof ContextClosedEvent) {
			System.out.println("this is ContextClosedEvent ......");
		}
		
	}

> 5. ApplicationListener<ContextRefreshedEvent>

說明：監聽 ContextRefreshedEvent 事件，一旦 Spring 容器初始化完成，就會發送 ContextRefreshedEvent。

@Configuration
public class initializeFour implements ApplicationListener<ContextRefreshedEvent>{

	@Override
	public void onApplicationEvent(ContextRefreshedEvent event) {
		// TODO Auto-generated method stub
		if(event.getApplicationContext().getParent() == null) {
			System.out.println("this is ContextRefreshedEvent ......");
		}
	}
	
}

啓動程序，運行結果如下：