Thanks Frank, obviously I made test and used alerts and saw lines numbers and I didn´t found the error.
Of that 100 implementions that I can quickly find in Google, can you give me two links (more if possible), to make that an application that was made in struts, and it's already finnished, in which I can´t change the architecture or logic, only can change de JSPs, was able to use Ajax?? Thanks p.d: i'm checking javawebparts