Render Facelets Programmatically

July 16, 2011

Render Facelets Programmatically

Recently I have been trying to build the ability to send e-mails in a JSF project. Since Facelets is a great templating technology, I want to render the e-mails with Facelets. To my surprise, this isn’t an easy thing to do.

I started by following the solution documented here. On my Apache MyFaces 2.1.1 setup, the result was empty — nothing would be rendered. After spending a few hours poking around the source code of MyFaces, it revealed that ViewDeclarationLanguage.buildView() needed to be called first. The content would now be rendered. This made me happy for about 30 minutes.

After 30 minutes, there was a second challenge. For whatever reason, calling renderView() screws up MyFaces’ response to AJAX calls. Not being able to send out e-mails when the action is triggered by an AJAX call would be a great annoyance.

In order to fix the problem, I needed to find a replacement for the renderView() call. It turned out that Seam framework’s solution was to traverse and render the components manually, instead of calling renderView() directly. It worked great!

So, my final code for rendering Facelets looks like this:

A bonus of this solution is that there is no need to capture the output via a fake response object. Since the output gets written to ResponseWriter when the components are encoded, building a ResponseWriter with a StringWriter would allow the result to be extracted.

This solution has been tested to work on MyFaces 2.1.1 and Mojarra 2.1.2.

Update Aug. 11, 2011: a usage example is available here.

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