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

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

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/**
 * Copyright (C) 2012 Ryan W Tenney (ryan@10e.us)
 *
 * 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 org.springframework.core.Ordered;
import org.springframework.util.ReflectionUtils;

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

import static com.ryantenney.metrics.spring.AnnotationFilter.INSTANCE_FIELDS;

class GaugeFieldAnnotationBeanPostProcessor extends AbstractAnnotationBeanPostProcessor implements Ordered {

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

    private final MetricRegistry metrics;

    public GaugeFieldAnnotationBeanPostProcessor(final MetricRegistry metrics) {
        super(Members.ALL, Phase.PRE_INIT, FILTER);
        this.metrics = metrics;
    }

    @Override
    protected void withField(final Object bean, String beanName, Class<?> targetClass, final Field field) {
        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());
    }

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

}