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servletsweb.xmlcustom-error-pages

<error-page> tag in web.xml doesn't catch java.lang.Throwable Exceptions

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.xml file in this way:

<error-page>
    <error-code>404</error-code>
    <location>/error.jsp</location>
</error-page>
<error-page>
    <exception-type>java.lang.Throwable</exception-type>
    <location>/error.jsp</location>
</error-page>

When I rise a 404 error, then it works and calls error.jsp, but when I rise a java.lang.IllegalArgumentException, then it does not work and I've a blank page instead of error.jsp. Why?

The server is Glassfish, and logs show really IllegalArgumentException rised.

Solution

  • 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: