Most web programmers use a logging framework and handle unexpected errors by reporting them through a static reporting object and forwarding the user to an error page.

My code for reporting an unexpected exception looks something like this:

       public static synchronized void report(Throwable e) {
            ByteArrayOutputStream logResult = new ByteArrayOutputStream();
            e.printStackTrace(new PrintStream(logResult));
            logger.error(logResult.toString());
       }
    

Logging helps me identify problems by examining the logs for errors and figuring out what is happening. The problem this method is that I don't examine the logs until someone reports a problem. It would be really nice to figure out that I have an error before most of my users do. The best way I've found to do is to email the error log to myself using Java Mail API.

I like to send email errors only to myself, because I always find problems that aren't really problems at all (eg: user closed their browser during a request). I've found that sending error emails out to people who aren't used to checking code gets me a gaggle of chicken little helpers in my office that keep me from actually figuring out if the latest exception was a real problem or not.

Another nice trick I like to do is add the machine name in the mail subject. I use the command, "InetAddress.getLocalHost().getHostName()," to get the local host and set up a filter that separates my dev, test and production instances. On a production instance if something goes seriously wrong, then if I'm at my desk, I will learn about the problem before my users and can address it before the any chicken little is any the wiser.