Spring Session event事件分析

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