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本文主要介绍下如何在spring中进行发布时间以及接收事件

定义事件

public class DemoEvent extends ApplicationEvent {    private String message;    public DemoEvent(Object source, String message) {        super(source);        this.message = message;    }    public String getMessage() {        return message;    }}

发布事件

@Autowired    private ApplicationEventPublisher applicationEventPublisher;    @GetMapping("/send-event")    public Object sendEvent(@RequestParam String msg){        DemoEvent demoEvent = new DemoEvent(this,msg);        applicationEventPublisher.publishEvent(demoEvent);        LOGGER.info("finish publish event");        return "success";    }

这里在mvc中发布，仅仅是为了演示。

接收事件(默认同步)

@Componentpublic class DemoEventListener implements ApplicationListener
    
     {    private static final Logger LOGGER = LoggerFactory.getLogger(DemoEventListener.class);    @Override    public void onApplicationEvent(DemoEvent demoEvent) {        LOGGER.info("receive event:{}",demoEvent.getMessage());    }}
    

这里是同步接收

异步处理事件

@Configurationpublic class AsyncEventConfig {    @Bean(name = "applicationEventMulticaster")    public ApplicationEventMulticaster simpleApplicationEventMulticaster() {        SimpleApplicationEventMulticaster eventMulticaster                = new SimpleApplicationEventMulticaster();        eventMulticaster.setTaskExecutor(new SimpleAsyncTaskExecutor());        return eventMulticaster;    }}

加上这个配置就ok了，不然要注意，这里自己new的task executor，要优雅关闭的话，需要自己shutdown

SimpleApplicationEventMulticaster

spring-context-4.3.11.RELEASE-sources.jar!/org/springframework/context/event/SimpleApplicationEventMulticaster.java

@Override    public void multicastEvent(ApplicationEvent event) {        multicastEvent(event, resolveDefaultEventType(event));    }    @Override    public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {        ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));        for (final ApplicationListener
     listener : getApplicationListeners(event, type)) {            Executor executor = getTaskExecutor();            if (executor != null) {                executor.execute(new Runnable() {                    @Override                    public void run() {                        invokeListener(listener, event);                    }                });            }            else {                invokeListener(listener, event);            }        }    }    private ResolvableType resolveDefaultEventType(ApplicationEvent event) {        return ResolvableType.forInstance(event);    }

可以看到，使用applicationEventMulticaster的时候，如果有线程池，则用线程池异步执行；否则则知直接调用listener的执行方法同步执行。

doc