Struts2在重定向后ActionErrors和ActionMessage丢失问题

Step1：把 B Action的信息储存到Session中去
        

     /**
	 * Store action messages and errors.
	 */
	protected void storeActionMessagesAndErrors() {
		Collection<String> actionMessages = this.getActionMessages();
		if (CollectionUtils.isNotEmpty(actionMessages)) {
			this.setToSession(Constants.SESSION_ACTION_MESSAGES,
					actionMessages);
		}
		Collection<String> actionErrors = this.getActionErrors();
		if (CollectionUtils.isNotEmpty(actionErrors)) {
			this.setToSession(Constants.SESSION_ACTION_ERRORS,
					this.getActionErrors());
		}
	}
        /**
	 * Set an object in the session.
	 * 
	 * @param key
	 *            the object key
	 * @param object
	 *            the object to set.
	 */
	protected void setToSession(String key, Object object) {
		ServletActionContext.getRequest().getSession()
				.setAttribute(key, object);
	}

Step2:在从B Action重定向A Action的时候，在从Session中取出来

         /**
	 * Retrieve action messages.
	 */
	@SuppressWarnings("unchecked")
	protected void retrieveActionMessagesAndErrors() {
		Collection<String> actionErrorsRetrieved = (Collection<String>) this
				.getFromSession(Constants.SESSION_ACTION_ERRORS);
		Collection<String> actionMessagesRetrieved = (Collection<String>) this
				.getFromSession(Constants.SESSION_ACTION_MESSAGES);
		if (actionErrorsRetrieved != null) {
			Collection<String> actionErrors = this.getActionErrors();
			actionErrors.addAll(actionErrorsRetrieved);
			this.setActionErrors(actionErrors);
			this.removeSession(Constants.SESSION_ACTION_ERRORS);
		}
		if (actionMessagesRetrieved != null) {
			Collection<String> actionMessages = this.getActionMessages();
			actionMessages.addAll(actionMessagesRetrieved);
			this.setActionMessages(actionMessages);
			this.removeSession(Constants.SESSION_ACTION_MESSAGES);
		}
	}

	/**
	 * 
	 * Get an object from Session.
	 * 
	 * @param key
	 *            the object key.
	 * @return the object.
	 */
	protected Object getFromSession(String key) {
		return ServletActionContext.getRequest().getSession().getAttribute(key);
	}

	/**
	 * Removes the session.
	 * 
	 * @param key
	 *            the key
	 */
	protected void removeSession(String key) {
		ServletActionContext.getRequest().getSession().removeAttribute(key);
	}