Is PrimceFaces 3.1 Backward Compatible to 2.x version - jsf-2

Question

I'm developing a web app using JSF 2.0 + PrimeFaces 2.2.1
Now I think PrimeFaces 3.x is stable enough. (3.1)
Can I replace the library (PrimeFaces jar file) and continue the development. I know some features have been re-invented in PrimeFaces 3.1.
Will this change make any problem to my app?

Answer 1

You can find the main changes in PrimeFaces 2.2 --> 3.0 in the PrimeFaces wiki. Here's an extract of relevance:
General Changes
Taglib namespaces are changed as;
http://primefaces.prime.com.tr/ui -> http://primefaces.org/ui
http://primefaces.prime.com.tr/mobile -> http://primefaces.org/mobile
Note that this change applies 3.0.M4 and newer.
Component events are now decoupled and implemented as ajax behaviors to improve flexibility. Read more at here. Common *Listener and *Update attributes are now removed, an example is rating component;
2.x;
<p:rating value="#{ratingController.ratingValue}" rateListener="#{ratingController.handleRate}" update="messages"/>
3.x;
<p:rating value="#{ratingController.ratingValue}">
<p:ajax event="rate" listener="#{ratingController.handleRate}" update="messages" />
</p:rating>
User's guide and Taglib docs(IDE completion) will provide all the available events of a component.
RequestContext now allows to execute javascript from backing beans (e.g. deciding to keep a dialog open or hide it), In 2.x this conditional javascript execution on callbacks like oncomplete are achieved via callback params, execute("script here") makes it very easy to implement the same compared to callback params. Note that callback params are still supported and will be in future as they are also used internally in PrimeFaces.
Tag/Attribute docs are available again in facelet taglib to take advantage of quick documentation via IDE code completion.
Aristo replaced Sam as the built-in theme, sam is available at theme gallery as a downloadable theme.
You can find the main changes in PrimeFaces 3.0 --> 3.1 in this PrimeFaces blog. Here's an extract of relevance:
Backward Compatibility
There are two points to note regarding backward compatibility with 3.0;
Component referencing is now aligned with JSF Spec, if PrimeFaces cannot find a component, it will throw an exception. Since PrimeFaces 2.2 we’ve been logging an info message that component cannot be found and falling back to the client id. If you haven’t ignored these messages and fixed your code since 2.2, there won’t be a problem. If not, you need to update your component referencing with respect to findComponent specification.
primefaces.THEME_FORMS setting is removed in favor of plain css, if you need to reset the theme aware styles on input components, add a reset css instead.