A not too uncommon runtime error occurs by trying to call response.sendRedirect(…) twice on a single JSP or calling response.sendRedirect(…) while writing any output to a servlet or JSP output stream.

A trick that I use to avoid this problem is to simply ‘return’ immediately after calling response.sendRedirect(…). This is required because the page is not redirected instantly – it occurs after all the output to the page is written.

Simple trick, but I never see this in other people’s JSP code, so I thought that it was worth mentioning it.