1. org.apache.catalina.session.StandardSession 这是servlet-api jar包中的一个类。是session接口的标准实现。当session创建的时候会通知监听者,同理，session销毁的时候也会产生事件，代码如下：
/**
* Inform the listeners about the new session.
*
*/
public void tellNew() { // Notify interested session event listeners
fireSessionEvent(Session.SESSION_CREATED_EVENT, null); // Notify interested application event listeners
Context context = (Context) manager.getContainer();
Object listeners[] = context.getApplicationLifecycleListeners();
if (listeners != null) {
HttpSessionEvent event =
new HttpSessionEvent(getSession());
for (int i = 0; i < listeners.length; i++) {
if (!(listeners[i] instanceof HttpSessionListener))
continue;
HttpSessionListener listener =
(HttpSessionListener) listeners[i];
try {
context.fireContainerEvent("beforeSessionCreated",
listener);
listener.sessionCreated(event);
context.fireContainerEvent("afterSessionCreated", listener);
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
try {
context.fireContainerEvent("afterSessionCreated",
listener);
} catch (Exception e) {
// Ignore
}
manager.getContainer().getLogger().error
(sm.getString("standardSession.sessionEvent"), t);
}
}
} }
2. 上面标红的session event监听器哪里来的呢？答案是web.xml。我们需要在web.xml中添加如下配置：
<listener>
<listener-class>org.springframework.security.web.session.HttpSessionEventPublisher</listener-class>
</listener>
3. 接着，在HttpSessionEventPublisher中，从HttpSessionEvent中获取session,再从session中获取ServletContext，进而获取spring 容器（ApplicationContext)，然后往容器发送event,代码如下：
/**
* Handles the HttpSessionEvent by publishing a {@link HttpSessionCreatedEvent} to the
* application appContext.
*
* @param event HttpSessionEvent passed in by the container
*/
public void sessionCreated(HttpSessionEvent event) {
HttpSessionCreatedEvent e = new HttpSessionCreatedEvent(event.getSession());
Log log = LogFactory.getLog(LOGGER_NAME); if (log.isDebugEnabled()) {
log.debug("Publishing event: " + e);
} getContext(event.getSession().getServletContext()).publishEvent(e);
}
AbstractApplicationContext.java: 事件发布
protected void publishEvent(Object event, ResolvableType eventType) {
Assert.notNull(event, "Event must not be null");
if (logger.isTraceEnabled()) {
logger.trace("Publishing event in " + getDisplayName() + ": " + event);
}
// Decorate event as an ApplicationEvent if necessary
ApplicationEvent applicationEvent;
if (event instanceof ApplicationEvent) {
applicationEvent = (ApplicationEvent) event;
}
else {
applicationEvent = new PayloadApplicationEvent<Object>(this, event);
if (eventType == null) {
eventType = ((PayloadApplicationEvent)applicationEvent).getResolvableType();
}
}
// Multicast right now if possible - or lazily once the multicaster is initialized
if (this.earlyApplicationEvents != null) {
this.earlyApplicationEvents.add(applicationEvent);
}
else {
getApplicationEventMulticaster().multicastEvent(applicationEvent, eventType); // 通过事件广播器广播事件
}
// Publish event via parent context as well...
if (this.parent != null) {
if (this.parent instanceof AbstractApplicationContext) {
((AbstractApplicationContext) this.parent).publishEvent(event, eventType);
}
else {
this.parent.publishEvent(event);
}
}
}
SimpleApplicationEventMulticaster: 应用事件广播器
@Override
public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {
ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) { // 根据event和type找到对应的监听器，并通知监听器
Executor executor = getTaskExecutor();
if (executor != null) {
executor.execute(new Runnable() {
@Override
public void run() {
invokeListener(listener, event);
}
});
}
else {
invokeListener(listener, event);
}
}
}
4. spring 事件的消费者 ApplicationEventListener extend EventListener