A Flash in the Pan?

JSF 2 introduces an EL variable flash. Anything you set persists for one post-redirect-get cycle. (In contrast, anything in the request scope is gone after a redirect.) A typical use of the flash is for messages. A managed bean method might put a message in the flash, ExternalContext.getFlash().put("warning", "Your password is about to expire"); Then the message can be displayed on the next page as #{flash.warning} That's handy—the message survives one redirect, and then it is gone. But it also points to a weakness of the flash. It doesn't really fit into the managed bean model. Normally, I would put a message in a managed bean object, without using the JSF API. Then I'd use it as #{myPage.warning}. In the published uses of the flash, you always see unsightly code in which data are shoveled in or out of the flash. Of course, I'd want the myPage bean to go away soon, and do so automatically. Maybe a CDI FlashScope is in order, so that I can do @Named @FlashScoped public class MyPage There is a discussion about this on the Seam 3 board. Similar to Rails, the JSF 2 flash allows you to keep an entry for another cycle, by using #{flash.keep.key} This way, you can carry data along a page flow. You can have a data entry page with followed by a confirmation page with #{flash.keep.description} followed by another page that shovels the description into its final destination. (When I first saw this, I stared a...

Date: January, 12 2010
Url: http://www.java.net/blog/cayhorstmann/archive/2010/01/12/flash-pan

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