Hello and welcome to the forums, Huamin!
There are some things you have to have in mind when asking questions in forums, either here or outside. The readers of these forums are technical ones, of the type who appreciate seeing that you strived to do something, but failed, only then came up here for help. In other words, technical readers in the programming field appreciate seeing your unsuccessful attempts, the condition usually met so that you start receiving answers for your questions.
If you ask "How can I do something?" or "Give me an example of...", you're not likely to receive answers, also because such things may be found at Google through a simple search. As a real case scenario, I did a quick search at Google for "jsf bean binding" and took the first link to share here with you:
http://www.jsftutorials.net/components/step5.html. Take a look and check to see if it helps to bind a button to its respective Java class, or search a bit more on the web.
Cheers