Spring中@PostConstruct、@PreDestroy、InitializingBean、DisposableBean、initMethod、des

最新推荐文章于 2023-11-29 16:51:25 发布

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最新推荐文章于 2023-11-29 16:51:25 发布

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分类专栏： spring 文章标签： java

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本文深入探讨了Spring框架中@PostConstruct、@PreDestroy等注解的执行顺序，以及与注入顺序的关系，通过具体示例展示了如何在Java层面自定义组件的生命周期。

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这次的博客比较Spring中@PostConstruct、@PreDestroy、InitializingBean、DisposableBean、initMethod、destoryMethod的执行顺序，顺便会将construct以及与注入顺序一并比较

为了方便起见，这次不使用xml文件定义bean，完全采用注解配置，共3个类，都放在annotations包下

下面是定义的两个bean，Bean2直接加上@Conponent注解，加入到ioc容器

而Bean1，有1个注入属性、1个普通属性、1个构造器、3个初始化方法、3个销毁方法

public class Bean1 implements InitializingBean, DisposableBean{
	
	@Autowired
	public Bean2 bean2;
	
	public String state;
	
	public Bean1 (){
		state = "construct!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}
	
	public void init_method (){
		state = "init-method!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}
	
	public void destory_method (){
		state = "destory-method!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}
	
	@PostConstruct 
	public void postConstruct (){
		state = "postConstruct!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}
	
	@PreDestroy 
	public void preDestory (){
		state = "preDestory!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}

	@Override
	public void destroy() throws Exception {
		state = "destory!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		state = "afterPropertiesSet!";
		System.out.println("bean1 -> " + state + "..." + "bean2: " + bean2);
	}

}

@Component
public class Bean2 {
	
}

不要奇怪为什么Bean1没有加入到ioc容器，我们下面马上进行：

@Configuration
@org.springframework.context.annotation.ComponentScan(basePackages = "annotations")
public class ComponentScan {
	
	@Bean(initMethod = "init_method", destroyMethod = "destory_method")
	public Bean1 bean1 (){
		return new Bean1();
	}

	public static void main(String[] args) {
		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
		ctx.register(ComponentScan.class);
		ctx.refresh();
		ctx.registerShutdownHook();
	}
	
}

可以通过@Configuration注册bean，和xml是一样的效果

打印结果为

bean1 -> construct!...bean2: null
bean1 -> postConstruct!...bean2: annotations.Bean2@35fc6dc4
bean1 -> afterPropertiesSet!...bean2: annotations.Bean2@35fc6dc4
bean1 -> init-method!...bean2: annotations.Bean2@35fc6dc4
bean1 -> preDestory!...bean2: annotations.Bean2@35fc6dc4
bean1 -> destory!...bean2: annotations.Bean2@35fc6dc4
bean1 -> destory-method!...bean2: annotations.Bean2@35fc6dc4

所以执行顺序如下：

初始化时：构造器Construct -> 属性注入 -> @PostConstruct -> InitializingBean接口 -> bean定义的initMethod

销毁时：@PreDestroy -> DisposableBean接口 -> bean定义的destoryMethod

When you work directly in Java, you can do anything you like with your objects and do not always need to rely on the container lifecycle!