fix @Gauge and @CachedGauge annotation BeanPostProcessor bugs and add more tests

[segeon]

When I try to config metrics-spring using JavaConfig and add @Gauge and @CachedGauge annotation on methods, I can't get their metric info through jmx. Other annotations like @counted, @metered, @timed work well. I looked into the source code, and find some problem that may be bugs.

In GaugeMethodAnnotationBeanPostProcessor line 28, the "return ReflectionUtils.invokeMethod(method, bean); " statement throw out java.lang.IllegalArgumentException: object is not an instance of declaring class. To my understanding, the argument bean is a proxy object, while method is the original Method object of the proxy target. We can't just call method like this. One simple solution is to find out the proxy object's corresponding Method and call it like this:

return ReflectionUtils.invokeMethod(bean.getClass().getMethod(method.getName(), method.parameterTypes), bean);

CachedGaugeAnnotationBeanPostProcessor class has the same problem and can be fixed in the same way.

[ryantenney]

Can you help me understand why you're referencing MBeans?

    …
    MBeanProxyFactoryBean factoryBean = new MBeanProxyFactoryBean();
    try {
        factoryBean.setObjectName(new ObjectName("metrics", "name", com.ryantenney.metrics.spring.javaconfig.MetricServiceImpl.gaugeValue"));
    }
    …

[segeon]

By referencing MBeans, I'm trying to ensure that the Metrics can produce right values through JMX reporter.

[ryantenney]

Okay, thanks for clarifying. I'd rather not do any JMX testing in this project, as it's already thoroughly tested by JmxReporterTest in Metrics.

The resolution of the issue you're seeing shouldn't be to look up the method on every call to get/loadValue in the Gauge. Perhaps we can to check if the bean is an instance of Advised, and then grab the target object, and invoke the gauged method on that. I'll do some work on this and get back to you.

[selslack]

Any updates on this?

[madhurir12]

Any update on this issue? I am seeing the same error.