tag in web.xml doesn't catch java.lang.Throwable Exceptions

Question

I have a web-app developed with servlet & JSP. I configured my app to throw an IllegalArgumentException if I insert bad parameters. Then I configured my web

Answer 1

You should not catch and suppress it, but just let it go.

I.e. do not do:

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        doSomethingWhichMayThrowException();
    } catch (IllegalArgumentException e) {
        e.printStackTrace(); // Or something else which totally suppresses the exception.
    }
}

But rather just let it go:

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doSomethingWhichMayThrowException();
}

Or, if you actually intented to catch it for logging or so (I'd rather use a filter for that, but ala), then rethrow it:

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        doSomethingWhichMayThrowException();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
        throw e;
    }
}

Or, if it's not an runtime exception, then rethrow it wrapped in ServletException, it will be automatically unwrapped by the container:

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        doSomethingWhichMayThrowException();
    } catch (NotARuntimeException e) {
        throw new ServletException(e);
    }
}

See also:

• How does server prioritize which type of web.xml error page to use?
• Submitting form to Servlet which interacts with database results in blank page