Of all the MVC Frameworks I've developed with in the last few weeks (Struts, Spring MVC, WebWork and Tapestry) - JSF was by far the worst. And it's not the implementations that are the problem, it's the spec itself (as far as I can tell). Plain and simple, it does not simplify web development.
I spent 3 days developing a simple JSF app - most of it which I had done in the first day. The last 2 days have been spent migrating to MyFaces and trying to find clean ways to do things. My perspective on JSF after this experience? Run away. Run far, far away. All of the above mentioned frameworks are MUCH superior to this technology. Let's get on with the things I learned.
- MyFaces handles duplicate posts nicely. If you hit "reload" on your browser after saving a record, you get presented with an empty form rather than a duplicate record. I believe I got a duplicate record with Sun's RI.
- The ability to specify an "action" attribute on a button (or a link) and them map that action to a page (in faces-config.xml) is pretty cool.
- Every button or link clicked results in a form post. That's just wrong - why can't I have true links like the web is supposed to? So much for bookmarks.
- Saving state on the client results in enormously long URLs and/or hidden fields.
- JSF support is fairly non-existent. Unlike the other MVC frameworks, the MyFaces mailing list has hardly any traffic and the Sun forums aren't much better.
- The MyFaces website seems to be down whenever I want to look something up on it, like right now.
- I did find some CRUD examples, like this this one, but was disappointed to find that i18n is not considered for setting success messages. I ended up using the solution described in this post. 6 lines of code to set a success message - you've got to be kidding me! Most frameworks have a simple 1-2 liner.
- Waiting for JSPs to compile the first time has surprisingly become painful after using Tapestry, Velocity and FreeMarker for the last 2 weeks.
- Integration with Spring is fairly easy (code is in CVS), but MyFaces spits out an error when it shouldn't be.
- Validation messages are ugly. For instance, when a required field isn't filled in, I get: "lastName": Value is required. I was able to override the default messages, but I was never able to use the label of the field (vs. the field's id).
- The <h:messages> tag is practically worthless. Sure it's great for displaying messages (error and success), but that's about it. It has a "layout" attribute that doesn't even work in Sun's RI, and in MyFaces it just wraps a <span> with a <ul><li> or a <table>. Both of these layouts are useless b/c you can't set a css class on them. I ended up using "table" and having to set a generic CSS rule (width: 100%) in order to get the message/error bar to show across the top of my page. This tag also doesn't allow you to escape HTML.
- The <h:dataTable> component is nothing like the displaytag. MyFaces claims to have a pageable/sortable component, but it requires custom logic/methods in your managed-bean. Yuck. I ended up using <h:dataTable>, which has neither sorting or paging. This is only because I couldn't get an <h:commandLink> working inside a displaytag column.
- When using "ant reload" to reload my application (using Tomcat's Ant Tasks), I kept encountering a ThreadDeath error. This seems to be specific to MyFaces as I never saw it with other frameworks or Sun's RI.
My opinion after all of this? If you know Struts, Spring MVC and WebWork are fairly easy to learn. WebWork is simpler and elegant, but Spring MVC supports more view options out-of-the-box. Tapestry is cool, but you'll have to invest a lot of time into learning it and you'll probably get caught up in its cult and forever be claiming "Tapestry Rocks!" which can get annoying to your fellow developers. Finally, I can confirm that SiteMesh rocks - it worked for all the frameworks I used and I never had to change a single line of code.
Whatever you do, don't use JSF. Not yet anyway.