Created
April 10, 2018 14:04
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Guice Dynamic Proxy Feature Toggles
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| @Target(PARAMETER) | |
| @Retention(RUNTIME) | |
| @BindingAnnotation | |
| public @interface Disabled {} |
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| @Target(PARAMETER) | |
| @Retention(RUNTIME) | |
| @BindingAnnotation | |
| public @interface Enabled {} |
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| @Target(TYPE) | |
| @Retention(RUNTIME) | |
| public @interface Feature { | |
| String key(); | |
| } |
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| public class FeatureFlipAnnotationTest { | |
| private static final Injector INJECTOR = Guice.createInjector(new FeatureFlipTestModule()); | |
| private static final SomeFeature SOME_FEATURE = INJECTOR.getInstance(SomeFeature.class); | |
| @Test | |
| public void test_enabled() { | |
| when(MOCK_FEATURE_FLIP.isFeatureEnabled("test_key")).thenReturn(true); | |
| assertThat(SOME_FEATURE.foo(), is("enabled")); | |
| } | |
| @Test | |
| public void test_disabled() { | |
| when(MOCK_FEATURE_FLIP.isFeatureEnabled("test_key")).thenReturn(false); | |
| assertThat(SOME_FEATURE.foo(), is("disabled")); | |
| } | |
| @Feature(key = "test_key") | |
| public interface SomeFeature { | |
| String foo(); | |
| } | |
| public static class EnabledImplementation implements SomeFeature { | |
| @Override | |
| public String foo() { | |
| return "enabled"; | |
| } | |
| } | |
| public static class DisabledImplementation implements SomeFeature { | |
| @Override | |
| public String foo() { | |
| return "disabled"; | |
| } | |
| } | |
| public static class SomeFeatureProvider extends FeatureFlipProxyProvider<SomeFeature> { | |
| @Inject | |
| public SomeFeatureProvider(FeatureFlip featureFlip, | |
| @Enabled SomeFeature enabledImplementation, | |
| @Disabled SomeFeature disabledImplementation) { | |
| super(SomeFeature.class, featureFlip, enabledImplementation, disabledImplementation); | |
| } | |
| } | |
| public static class FeatureFlipTestModule extends AbstractModule { | |
| public static final FeatureFlip MOCK_FEATURE_FLIP = mock(FeatureFlip.class); | |
| @Override | |
| protected void configure() { | |
| bind(FeatureFlip.class).toInstance(MOCK_FEATURE_FLIP); | |
| bind(SomeFeature.class).annotatedWith(Enabled.class).to(EnabledImplementation.class).in(SINGLETON); | |
| bind(SomeFeature.class).annotatedWith(Disabled.class).to(DisabledImplementation.class).in(SINGLETON); | |
| bind(SomeFeature.class).toProvider(SomeFeatureProvider.class); | |
| } | |
| } | |
| } |
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| public abstract class FeatureFlipProxyProvider<T> implements Provider<T> { | |
| private final T proxy; | |
| @SuppressFBWarnings("WEM_WEAK_EXCEPTION_MESSAGING") | |
| protected FeatureFlipProxyProvider(Class<T> type, | |
| FeatureFlip featureFlip, | |
| T enabledImplementation, | |
| T disabledImplementation) { | |
| Feature feature = type.getAnnotation(Feature.class); | |
| if (feature == null) { | |
| throw new IllegalArgumentException(type.getName() + " must be annotated with @Feature"); | |
| } | |
| String key = feature.key(); | |
| ClassLoader classLoader = FeatureFlipProxyProvider.class.getClassLoader(); | |
| Class<?>[] interfaces = {type}; | |
| proxy = (T) Proxy.newProxyInstance(classLoader, interfaces, | |
| (proxy1, method, args) -> featureFlip.isFeatureEnabled(key) ? | |
| method.invoke(enabledImplementation, args) : | |
| method.invoke(disabledImplementation, args)); | |
| } | |
| @Override | |
| public T get() { | |
| return proxy; | |
| } | |
| } |
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