Spring Event & SpringBoot Event 示例

最近看到有说 Spring Event和SpringBoot Event两种 Event
仔细看才知道，他们将SpringApplication中新增的SpringApplicationRunListener 视为是SpringBoot Event的处理类，而以往实现ApplicationListener的称为Spring Event

这么分有些道理，毕竟 SpringApplicationRunListener是SpringBoot新引进的，且在SpringApplication的run()方法中进行调用，并且初始化在onRefresh()之前。那我姑且接受这一分类方式

具体原理不做说明，可以参考SpringBoot中的事件机制

自定义Spring Event 示例

自定义 Spring Event 可以自定义 Event、publisher和listener


public class ISpringEvent extends ApplicationEvent {
    /**
     * Create a new ApplicationEvent.
     *
     * @param source the object on which the event initially occurred (never {@code null})
     */
    public ISpringEvent(Object source) {
        super(source);
    }
}

@Component
public class ISpringEventPublisher {

    @Autowired
    private ApplicationEventPublisher publisher;


    public void publish(){
        ISpringEvent springEvent = new ISpringEvent(this);
        publisher.publishEvent(springEvent);
    }

}

// 实现接口方式
@Component
public class ISpringEventListener implements ApplicationListener<ISpringEvent> {
    @Override
    public void onApplicationEvent(ISpringEvent event) {

        System.out.println("This is event listener");

    }
}
// 注解实现方式
@Component
public class ISpringAnnotationEventListener {

    @EventListener(classes = ISpringEvent.class)
    public void onEvent(){
        System.out.println("This is Annotation Event listener");
    }
}

运行结果:

This is Annotation Event listener
This is event listener

自定义SpringBoot Event 示例

其实这篇随笔最主要是为了记录这里的一个坑

自定义SpringBoot Event的时候，由于SpringApplication#getRunListener 方法里指定了其构造函数的参数为
SpringApplication和String[]，因此一直要自定义一个构造函数

private SpringApplicationRunListeners getRunListeners(String[] args) {
              // 构造函数的参数数组
        Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
        return new SpringApplicationRunListeners(logger,
                getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
    }

因此必须实现一个(SpringApplication application, String[] args)的构造函数

否则会保错Caused by: java.lang.NoSuchMethodException: com.wesley.xxx.springboot.ISpringBootListener.<init>(org.springframework.boot.SpringApplication, [Ljava.lang.String;)

则对应的代码为

public class ISpringBootListener implements SpringApplicationRunListener , Ordered {
    @Override
    public void starting() {
        System.out.println("context starting");
    }

    @Override
    public void environmentPrepared(ConfigurableEnvironment environment) {
        System.out.println("environment settled");
    }

    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {

    }

    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {

    }

    @Override
    public void started(ConfigurableApplicationContext context) {

    }

    @Override
    public void running(ConfigurableApplicationContext context) {

    }

    @Override
    public void failed(ConfigurableApplicationContext context, Throwable exception) {

    }

    @Override
    public int getOrder() {
        return 0;
    }
    public ISpringBootListener(SpringApplication application, String[] args) {
    }
}

并在配置文件META-INF/spring.factories中加上

org.springframework.boot.SpringApplicationRunListener=\
com.wesley.myannoation.event.springboot.ISpringBootListener

此时的Event的语句输出在启动日志里

最后编辑于：2020.09.16 10:24:49