Created
May 22, 2017 13:51
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Guice custom logger annotation without additional dependencies
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public class InjectLoggerTest { | |
@InjectLogger | |
private Logger logger; | |
public static void main(String[] args) throws Exception { | |
final Injector injector = Guice.createInjector(new ModuleInjectLogger()); | |
final InjectLoggerTest injectLoggerTest = injector.getInstance(InjectLoggerTest.class); | |
injectLoggerTest.f(); | |
} | |
@Inject | |
InjectLoggerTest(final Logger logger) { | |
this.logger = logger; | |
logger.warn("the fallback 'default' logger"); | |
} | |
private void f() { | |
logger.warn("the specific logger"); | |
} | |
} | |
@java.lang.annotation.Target({ FIELD }) | |
@Retention(RUNTIME) | |
@interface InjectLogger { | |
} | |
class ModuleInjectLogger extends AbstractModule { | |
@Override | |
protected void configure() { | |
bindListener(Matchers.any(), new ListenerInjectLogger()); | |
final Logger defaultLogger = LoggerFactory.getLogger("default"); | |
bind(org.slf4j.Logger.class).toInstance(defaultLogger); | |
} | |
} | |
class ListenerInjectLogger implements TypeListener { | |
@Override | |
public <I> void hear(final TypeLiteral<I> type, final TypeEncounter<I> encounter) { | |
Class<? super I> rawType = type.getRawType(); | |
while(rawType != null) { | |
for(final Field field : rawType.getDeclaredFields()) { | |
if( | |
field.getType() == Logger.class && | |
field.isAnnotationPresent(InjectLogger.class) | |
) { | |
final Logger logger = LoggerFactory.getLogger(field.getDeclaringClass()); | |
field.setAccessible(true); | |
encounter.register((MembersInjector<I>) instance -> { | |
try { | |
field.set(instance, logger); | |
} catch(final IllegalAccessException e) { | |
throw new RuntimeException(e); | |
} | |
}); | |
} | |
} | |
rawType = rawType.getSuperclass(); | |
} | |
} | |
} |
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