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ApplicationListenerDetector監聽器判斷demo

時間：2023-03-15來源：系統城裝機大師作者：佚名

判斷Bean是否是監聽器,如果是監聽器就將當前Bean加入監聽器集合

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21 public Object postProcessAfterInitialization(Object bean, String beanName) {
if (bean instanceof ApplicationListener) {
// potentially not detected as a listener by getBeanNamesForType retrieval
Boolean flag = this.singletonNames.get(beanName);
if (Boolean.TRUE.equals(flag)) {
// singleton bean (top-level or inner): register on the fly
this.applicationContext.addApplicationListener((ApplicationListener<?>) bean);
}
else if (Boolean.FALSE.equals(flag)) {
if (logger.isWarnEnabled() && !this.applicationContext.containsBean(beanName)) {
// inner bean with other scope - can't reliably process events
logger.warn("Inner bean '" + beanName + "' implements ApplicationListener interface " +
"but is not reachable for event multicasting by its containing ApplicationContext " +
"because it does not have singleton scope. Only top-level listener beans are allowed " +
"to be of non-singleton scope.");
}
this.singletonNames.remove(beanName);
}
}
return bean;
}

Bean銷毀之前

如果當前Bean是監聽器,就將當前Bean從監聽器集合中移除

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12 public void postProcessBeforeDestruction(Object bean, String beanName) {
if (bean instanceof ApplicationListener) {
try {
ApplicationEventMulticaster multicaster = this.applicationContext.getApplicationEventMulticaster();
multicaster.removeApplicationListener((ApplicationListener<?>) bean);
multicaster.removeApplicationListenerBean(beanName);
}
catch (IllegalStateException ex) {
// ApplicationEventMulticaster not initialized yet - no need to remove a listener
}
}
}