Just come back from testing center. Pass! Score is 91%, 63 out of 69.
Thanks Javaranch, JDiscuss and j2eeCertificate.
I used two books: "SCWCD exam study kit" and "Head first Servlet and JSP". I read through both of books three times. Personally, I think "study kit" is better to be used in the beginning of prepararion, and HFS provides better excises and tips.
In my case, the actual test is similar to the final mock in HFS. When I took the mock at the first time, I got 80%.
The parts of EL, JSTL, and Customer Tag are easier than my expectation, and similar to the questions in HFS.
I encountered a lot of questions related to response and reqeust API, DD and concepts of security. So put more time one them for your exam, please.
I spent two months preparing the exam. I took one month to read "Study kit" three times. At the beginning, one chapter each day. Then two chapters each day. It is ten days to go over "HFS" three times and take all mock exams in the book.