CODEWITHSUNDEEP
javaexceptiondependency-injectionguice
Drejc
Drejc

Reputation: 14286

How can I unwrap Guice ProvisionException?

In case and exception is thrown while Guice is creating a class a ProvisionException wraps the original exception.

Is there a way to force the throw of the original exception instead?

For instance:

@Inject
public myClass() {

  throw new MySpecificException();
}

I know, I can catch ProvisionException and call getCause() to unwrap and get to the MySpecificException. However, if possible I would prefer to override the default Guice exception instead.

Upvotes: 1

Views: 1130

Answers (1)

durron597
durron597

Reputation: 32323

No, you can't.

ProvisionException does a lot more than wrap one Exception; Guice is set up to catch many exceptions at once, roll them together into a single Exception and send a convenient, useful message back to you to figure out what went wrong.

For example, in the Guice source code there's lots of code like this:

try {
  result = callable.call();
  // Make sure we don't return the provisioned object if there were any errors
  // injecting its field/method dependencies.
  errors.throwIfNewErrors(numErrorsBefore);
} catch(ErrorsException ee) {
  exceptionDuringProvision = ee;
  throw new ProvisionException(errors.merge(ee.getErrors()).getMessages())
}

The error handling system is so deeply integrated that you're not going to be able to extract it out; and, honestly, why would you want to? The whole point of doing it this way is to make it easy for you to isolate the problem. If you're getting a ProvisionException, that means that your code is doing the wrong thing and needs to be changed; it is not the sort of thing that you can recover from and return to normal operations.

In my production system, I catch many exceptions in various places and handle them, log them and attempt to recover. But, ProvisionException is not one of them; if my system throws it, I want the whole darn thing to crash so I can figure it out immediately and fix it. (Of course, by the time I'm deploying a new build, it's been thoroughly tested so that I know, at the very least, if there is a problem it's not going to be ProvisionException).

Upvotes: 2

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