Question

I have a question on handling exception in web application. Often I hear catching the super class Exception is a bad idea.

Often I write codes to catch all exceptions in struts action / java servlet classes.

try {
     // call business facade
     // business facade calls DAO
     // any exception from DAO bubbles up 
} catch (Exception e) {
  log.error("error", e);
}

If we do not catch superclass Exception. How do we handle any unexpected runtime errors and logged them appropriately

Answer 1

You can setup a DefaultUncaughtExceptionHandler for your project to deal with uncaught exceptions. For example, this is a piece of code that I have in one of my projects:

private static void setDefaultUncaughtExceptionHandler() {
    try {
        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {

            @Override
            public void uncaughtException(Thread t, Throwable e) {
                logger.error("Uncaught Exception detected in thread {}", t, e);
            }
        });
    } catch (SecurityException e) {
        logger.error("Could not set the Default Uncaught Exception Handler", e);
    }
}