Try/Catch not catching exception

Question

I'm trying to do java class loading. I'm using eclipse (luna) with 1.8.0_25 on a macos yosemite.

I'm using the following code in order to do it. It's working, until it reaches a class that has a dependency that isn't contained inside the jar that I'm loading classes from. Neither on the environment.

I'm not interested in this classes, so, it's safe to ignore then. So, I put it inside a try/catch and just log it.

But, when the exception occurs, the execution is canceled.

The exception (summarized) is:

Exception in thread "main" java.lang.NoClassDefFoundError: org/aspectj/runtime/internal/AroundClosure

Caused by: java.lang.ClassNotFoundException: org.aspectj.runtime.internal.AroundClosure

It rises at the exact line that is inside the inner try/catch block.

Why? Shouldn't the try/catch just log it and move on?

URLClassLoader ucl = null;
try {
    URL url = Utils.getURIFromPath(jarFilePath).toURL();
    URL[] urls = new URL[] { url };
    ucl = new URLClassLoader(urls);
    for (String tmp : classes) {
        String clazz = tmp.substring(0, tmp.indexOf(".class")).replaceAll("/", ".");
        try {
            ucl.loadClass(clazz);
        } catch (Exception e) {
            LOGGER.error(e.getMessage(), e);
        }
    }
} catch (MalformedURLException e) {
    LOGGER.error(e.getMessage(), e);
} finally {
    if (ucl != null) {
        try {
            ucl.close();
        } catch (IOException e) {
            LOGGER.error(e.getMessage(), e);
        }
    }
}

Answer 1

NoClassDefFoundError is an Error, not an Exception, you should never¹ try to catch an error, as stated here, catching it won't help you.

Check your classpath and fix it.

¹ In some cases you might want to catch an error and handle it accordingly, as stated in the comments, maybe "never" is a little bit strong

Answer 2

Ok then try this:

catch (Throwable e) {
LOGGER.error(e.getMessage(), e);
}

Although using the above code will handle both Errors and Exceptions for you (both extend from Throwable), but it's not the right way to do it, only in very special cases do we handle errors using try-catch, errors are something we need to check in our code and resolve them.