All the semantic information you want is thrown away very early by Guice,
so there's probably not a way to get the kind of details that you want.
The internal implementation
<https://github.com/google/guice/blob/master/core/src/com/google/inject/internal/Errors.java>
uses
the same Message class that you see in the ProvisionException.
On Wednesday, 25 November 2015 03:46:36 UTC-5, jwa wrote:
>
> I would like to intercept some of the exceptions being thrown by Guice,
> with access to the full context of the underlying error, and use
> domain-specific details to come up with meaningful error messages.
>
> To illustrate this problem I am using a vastly simplified domain, this may
> be a bit tenuous, bear with me.
>
> I provide my clients with a simplified API which allows them to build-up
> the event without exposing them to the fact that Guice will be used to wire
> everything together:
>
> AthelticsBuilder builder = new AthelticsBuilder()
> .withTicketIssuer(ResultRecorded.class) // <-- This is a singleton,
> one ticket issuer per event
> .withObserver(ResultRecorded.class) // <--- This is race-scoped,
> one created per race
> .addRace("100 meter sprint")
> .build();
>
> Behind the scenes the AthleticsBuilder will use Guice to obtain instances
> of each of the classes described above. Framework-related dependencies may
> be injected into these classes, for example RaceObservers might want to
> gain access to the StopWatch that is timing the event they are responsible
> for observing:
>
> public class ResultRecorder implements RaceObserver {
> @Inject
> public ResultRecorder(Race race, StopWatch watch) { /* ... */ }
> }
>
> The injection of these race-specific dependencies is facilitated by a
> custom "RaceScope" which is entered/exited as the AthelticsBuilder creates
> each race added to the builder.
>
> It is possible for my API clients to make rather silly mistakes. For
> example, they might ask for a StopWatch to be injected into their
> TicketIssuer. This is not legal, as the TicketIssuer is a singleton, and
> has no access to members injected by the RaceScope. For eaxmple, if the
> following constructor is used:
>
> public class TicketMachine implements TicketIssuer {
>
> @Inject
> public TicketMachine(StopWatch watch) { /* ... */ }
> }
>
> Guice will throw a ProvisionException when attempting to instantiate the
> TicketMachine. This will have the following error:
>
> Caused by: com.google.inject.ProvisionException: Unable to provision, see
> the following errors:
>
> 1) Error in custom provider, com.google.inject.OutOfScopeException: Cannot
> access Key[type=com.acme.StopWatch, annotation=[none]] outside of a scoping
> block
> at com.acme.RaceScopeModule.configure(RaceScopeModule.java:25)
> while locating com.acme.StopWatch
> for parameter 0 at com.acme.TicketMachine.<init>(TicketMachine.java:85)
> while locating com.acme.TicketMachine
>
> This is rather unfortunate for two reasons:
>
> - It exposes my API clients to the fact I'm using Guice. My API
> completely insulates them from this, which is nice. It's only when errors
> are encountered that they suddenly become aware what's happening
> under-the-covers
> - The API consumer isn't likely to be able to decipher this error, and
> identifying the underlying issue
>
> It would be much nicer if I could intercept this exception (more likely
> the underlying exception) and provide something far more meaningful:
> "*TicketMachine
> cannot access com.acme.StopWatch as it does not have reference to a race*
> ".
>
> To be able to achieve this, I'd need to be able to intercept the exact
> details of the binding error. Simply catching ProvisionException is of
> little use to me; it just contains "Messages", which don't have any of the
> rich context-specific information I need to produce more meaningful errors.
>
> Is there some mechanism for handling / intercepting this errors, in order
> to produce more meaningful exceptions?
>
> Any pointers would be greatly appreciated.
>
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