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

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Here is the source code for com.ryantenney.metrics.spring.MetricAnnotationBeanPostProcessor.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.Counter;
import com.codahale.metrics.Histogram;
import com.codahale.metrics.Meter;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.Timer;
import com.ryantenney.metrics.annotation.Metric;

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

class MetricAnnotationBeanPostProcessor extends AbstractAnnotationBeanPostProcessor implements Ordered {

    private static final AnnotationFilter FILTER = new AnnotationFilter(Metric.class, INJECTABLE_FIELDS);

    private final MetricRegistry metrics;

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

    @Override
    protected void withField(Object bean, String beanName, Class<?> targetClass, Field field) {
        final Metric annotation = field.getAnnotation(Metric.class);
        final String metricName = Util.forMetricField(targetClass, field, annotation);

        final Class<?> type = field.getType();
        if (!com.codahale.metrics.Metric.class.isAssignableFrom(type)) {
            throw new IllegalArgumentException("Field " + targetClass.getCanonicalName() + "." + field.getName()
                    + " must be a subtype of " + com.codahale.metrics.Metric.class.getCanonicalName());
        }

        ReflectionUtils.makeAccessible(field);

        // Get the value of the field annotated with @Metric
        com.codahale.metrics.Metric metric = (com.codahale.metrics.Metric) ReflectionUtils.getField(field, bean);

        if (metric == null) {
            // If null, create a metric of the appropriate type and inject it
            metric = getMetric(metrics, type, metricName);
            ReflectionUtils.setField(field, bean, metric);
            LOG.debug("Injected metric {} for field {}.{}", metricName, targetClass.getCanonicalName(),
                    field.getName());
        } else {
            // If non-null, register that instance of the metric
            try {
                // Attempt to register that instance of the metric
                metrics.register(metricName, metric);
                LOG.debug("Registered metric {} for field {}.{}", metricName, targetClass.getCanonicalName(),
                        field.getName());
            } catch (IllegalArgumentException ex1) {
                // A metric is already registered under that name
                // (Cannot determine the cause without parsing the Exception's message)
                try {
                    metric = getMetric(metrics, type, metricName);
                    ReflectionUtils.setField(field, bean, metric);
                    LOG.debug("Injected metric {} for field {}.{}", metricName, targetClass.getCanonicalName(),
                            field.getName());
                } catch (IllegalArgumentException ex2) {
                    // A metric of a different type is already registered under that name
                    throw new IllegalArgumentException("Error injecting metric for field "
                            + targetClass.getCanonicalName() + "." + field.getName(), ex2);
                }
            }
        }
    }

    private com.codahale.metrics.Metric getMetric(MetricRegistry metricRegistry, Class<?> type, String metricName) {
        com.codahale.metrics.Metric metric;
        if (Meter.class == type) {
            metric = metrics.meter(metricName);
        } else if (Timer.class == type) {
            metric = metrics.timer(metricName);
        } else if (Counter.class == type) {
            metric = metrics.counter(metricName);
        } else if (Histogram.class == type) {
            metric = metrics.histogram(metricName);
        } else {
            throw new IllegalArgumentException("Invalid @Metric type " + type.getCanonicalName());
        }
        return metric;
    }

    @Override
    public int getOrder() {
        return LOWEST_PRECEDENCE - 2;
    }

}