What are jftfdi jffi doing to my query string?

Question

We are using JavaServer Faces 2.2 (Mojarra 2.2.1) in our project. I noticed something odd. On a page called reporting.xhtml where I use f:metadata

Answer 1

It's part of the new JSF 2.2 feature as described by spec issue 949. Basically, it enables JSF to identify the client window. It's basically the same as cid in CDI's @ConversationScoped and windowId in CODI's @ViewScoped/@ViewAccessScoped. This client window ID is in turn used by among others the new JSF 2.2 @FlowScoped scope as described by spec issue 730.

The "What's new in JSF 2.2?" article of my fellow Arjan Tijms explains the need pretty clearly:

LifeCycle

Identify client windows via a Window Id

Arguably one of the biggest problems that has been plaguing web application development since its inception is the inability to distinguish requests originating from different windows of a single browser. Not only has an actual solution been long overdue, it has taken a long time to realize this even was a problem.

The root of the problem, as always, is that the HTTP protocol is inherently stateless while applications in general are not. There is the concept of a cookie though, which is overwhelmingly the mechanism used to distinguish requests from different users and to implement things like a session scope where on its turn the bulk of login mechanisms are based on.

While a cookie does work for this, it’s global per browser and domain. If a user opens multiple tabs or windows for the same domain then requests from those will all send the same cookie to the server. Logging in as a different user in a different window for the same website is thus not normally possible, and having workflows (involving post-backs, navigation) in different windows can also be troublesome because of this.

In JSF there are various solutions that are somehow related to this. The view scope effectively implements a session per window as long as the user stays on the same page and does only post-backs. The Flash is used for transferring data between different pages (presumably within the same window) when navigation is done via Redirect/GET. There’s a wide variety of scopes implemented by third parties that do something similar.

All of these have some implicit notion or assumption of the concept of a ‘client window’, but there is no explicit API for this.

JSF 2.2 will introduce support for two different aspects of this:

• Identification of an individual window: the Client Window Id
• API and life-cyle awareness of the window concept

Apparently you've configured your application as such.

See also:

• What's new in JSF 2.2? - Lifecycle - Identify client windows via window Id
• What's new in JSF 2.2? - Navigation - Faces Flow