package com.palominolabs.metrics.guice;
import com.codahale.metrics.Meter;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.annotation.ExceptionMetered;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import java.lang.reflect.Method;
/**
* A method interceptor which creates a meter for the declaring class with the given name (or the
* method's name, if none was provided), and which measures the rate at which the annotated method
* throws exceptions of a given type.
*/
class ExceptionMeteredInterceptor implements MethodInterceptor {
static MethodInterceptor forMethod(MetricRegistry metricRegistry, Class<?> klass, Method method) {
final ExceptionMetered annotation = method.getAnnotation(ExceptionMetered.class);
if (annotation != null) {
final Meter meter = metricRegistry.meter(determineName(annotation, klass, method));
return new ExceptionMeteredInterceptor(meter, annotation.cause());
}
return null;
}
private static String determineName(ExceptionMetered annotation, Class<?> klass, Method method) {
if (annotation.absolute()) {
return annotation.name();
}
if (annotation.name().isEmpty()) {
return MetricRegistry.name(klass, method.getName(), ExceptionMetered.DEFAULT_NAME_SUFFIX);
}
return MetricRegistry.name(klass, annotation.name());
}
private final Meter meter;
private final Class<? extends Throwable> klass;
private ExceptionMeteredInterceptor(Meter meter, Class<? extends Throwable> klass) {
this.meter = meter;
this.klass = klass;
}
@Override
public Object invoke(MethodInvocation invocation) throws Throwable {
try {
return invocation.proceed();
} catch (Throwable t) {
if (klass.isAssignableFrom(t.getClass())) {
meter.mark();
}
throw t;
}
}
}