com.ryantenney.metrics.spring.GaugeAnnotationBeanPostProcessor.java Source code

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Here is the source code for com.ryantenney.metrics.spring.GaugeAnnotationBeanPostProcessor.java

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/*
 * Copyright 2012 Ryan W Tenney (http://ryan.10e.us)
 *            and Martello Technologies (http://martellotech.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.ryantenney.metrics.spring;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.Ordered;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.ReflectionUtils.FieldCallback;
import org.springframework.util.ReflectionUtils.MethodCallback;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.annotation.Gauge;

class GaugeAnnotationBeanPostProcessor implements BeanPostProcessor, Ordered {

    private static final Logger LOG = LoggerFactory.getLogger(GaugeAnnotationBeanPostProcessor.class);

    private static final AnnotationFilter FILTER = new AnnotationFilter(Gauge.class);

    private final MetricRegistry metrics;

    public GaugeAnnotationBeanPostProcessor(final MetricRegistry metrics) {
        this.metrics = metrics;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) {
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(final Object bean, String beanName) {
        final Class<?> targetClass = AopUtils.getTargetClass(bean);

        ReflectionUtils.doWithFields(targetClass, new FieldCallback() {
            @Override
            public void doWith(final Field field) throws IllegalAccessException {
                ReflectionUtils.makeAccessible(field);

                final Gauge annotation = field.getAnnotation(Gauge.class);
                final String metricName = Util.forGauge(targetClass, field, annotation);

                metrics.register(metricName, new com.codahale.metrics.Gauge<Object>() {
                    @Override
                    public Object getValue() {
                        Object value = ReflectionUtils.getField(field, bean);
                        if (value instanceof com.codahale.metrics.Gauge) {
                            value = ((com.codahale.metrics.Gauge<?>) value).getValue();
                        }
                        return value;
                    }
                });

                LOG.debug("Created gauge {} for field {}.{}", metricName, targetClass.getCanonicalName(),
                        field.getName());
            }
        }, FILTER);

        ReflectionUtils.doWithMethods(targetClass, new MethodCallback() {
            @Override
            public void doWith(final Method method) throws IllegalAccessException {
                if (method.getParameterTypes().length > 0) {
                    throw new IllegalStateException(
                            "Method " + method.getName() + " is annotated with @Gauge but requires parameters.");
                }

                final Gauge annotation = method.getAnnotation(Gauge.class);
                final String metricName = Util.forGauge(targetClass, method, annotation);

                metrics.register(metricName, new com.codahale.metrics.Gauge<Object>() {
                    @Override
                    public Object getValue() {
                        return ReflectionUtils.invokeMethod(method, bean);
                    }
                });

                LOG.debug("Created gauge {} for method {}.{}", metricName, targetClass.getCanonicalName(),
                        method.getName());
            }
        }, FILTER);

        return bean;
    }

    @Override
    public int getOrder() {
        return LOWEST_PRECEDENCE;
    }

}