JSP error page from servlet

We can invoke the JSP error page and pass the exception object to it from within a servlet. The trick is to create a request dispatcher for the JSP error page, and pass the exception object as a javax.servlet.jsp.jspException request attribute. However, note that you can do this from only within controller servlets.

If your servlet opens an OutputStream or PrintWriter, the JSP engine will throw the following translation error:
java.lang.IllegalStateException: Cannot forward as OutputStream or Writer has already been obtained.

The following code snippet demonstrates the invocation of a JSP error page from within a controller servlet:

protected void sendErrorRedirect(HttpServletRequest request,
HttpServletResponse response, String errorPageURL, Throwable e) throws
ServletException, IOException {
request.setAttribute ("javax.servlet.jsp.jspException", e);
getServletConfig().getServletContext().
getRequestDispatcher(errorPageURL).forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
{
try {
// do something
} catch (Exception ex) {
try {
sendErrorRedirect(request,response,"/jsp/MyErrorPage.jsp",ex);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Some More Information -
1. Error page is jsp page and there is tag called IsErrorPage = True.
2. To set the port for server, you just go to server /default/deploy/tomacat5.5.rar/server.xml. Inside server.xml you can see Tag
8080. Give some other name apart from 8080.