| Qualifier and Scope annotations are used by dependency injection frameworks to |
| adjust their behavior. Not having runtime retention on scoping or qualifier |
| annotations will cause unexpected behavior in frameworks that use reflection: |
| |
| ```java |
| class CreditCardProcessor { @Inject CreditCardProcessor(...) } |
| |
| @Qualifier |
| @interface ForTests |
| |
| @Provides |
| @ForTests |
| CreditCardProcessor providesTestProcessor() { return new TestCreditCardProcessor(...) } |
| ... |
| |
| @Inject |
| MyApp(CreditCardProcessor processor) { |
| processor.issueCharge(...); // Issues a charge against a fake! |
| } |
| ``` |
| |
| Since the Qualifier doesn't have runtime retention, the Guice provider method |
| doesn't see the annotation, and will use the TestCreditCardProcessor for the |
| normal CreditCardProcessor injection point. |
| |
| NOTE: Even for dependency injection frameworks traditionally considered to be |
| compile-time dependent, the JSR-330 specification still requires runtime |
| retention for both [`Qualifier`] and [`Scope`]. |
| |
| [`Qualifier`]: http://docs.oracle.com/javaee/6/api/javax/inject/Qualifier.html |
| [`Scope`]: http://docs.oracle.com/javaee/6/api/javax/inject/Scope.html |
