Embracing an exception

The Exception class includes various methods that help you better understand why an exception was thrown. You can even find out the type of exception, what line of Apex code caused the exception, and even get the entire stack trace. In addition to the built-in exception types, Apex includes the ability to create your own exception types. This allows you to catch a system exception, evaluate it, and throw your own custom exception. Although it involves slightly more work, a custom exception type can be the difference between frantically debugging code in the middle of the night and sleeping like a baby. Imagine writing code to integrate with an outside system. There are times where that process will fail (like when the other system is under maintenance). If you proactively throw your own exception, you'll immediately know why it failed. The following code will show you how to define a custom exception type:

//Define our custom Exception type
Public class myCustomException extends Exception{}

//Try calling out to our outside system
try {
httpRequest req = new httpRequest();
//You have to whitelist the endpoint in Setup|Remote Site Settings
req.setEndpoint('http://www.madeUpUrl.net');
req.setMethod('GET');
//Set the timeout to 1 millisecond to force an exception
req.setTimeout(1);
httpResponse res = new http().send(req);
} catch ( Exception e){
if (e.getTypeName() == 'System.CalloutException' && e.getMessage() == 'Read timed out'){
  throw new myCustomException('Go Back to Sleep', e);
} else {
  throw e;
}
}