Tag reuse by server

Question

private int i = 0;
public int doStartTag() throws JspException {
     try {
          pageContext.getOut().println(i++);
     } catch (IOException e) {
          e.printStackTrace();
     return EVAL_BODY_INCLUDE;
}Would provide a sort of counter upon each refresh. I was under the impression that tags would not keep this information. If I were to set an internal variable with a user's private information, would this mean that the next user may access it? What about optional attributes (are they set to null)? And would these tags ever be used at the same time by two users? (Which would of course be worse than a reuse, as setting all data to null afterwards would not help).
How are tags reused, and what should and shouldn't I worry about?
I'm using Apache Tomcat 5.5.3

Answer 1

I believe that tags don't have to be thread safe (which is what you're asking about correct?) because the container will instantiate another tag object if needed for a different request. You can check this out by usign a debugger and inserting a breakpoint in your tag class and watch how the servlet container creates another instance of the tag class. However, instances of your tag class will be re-used so you should make sure that you overload the release() method from TagSupport to reset all local class member variables to their "starting" value.