server/mailet/mailets/src/main/java/org/apache/james/transport/mailets/MetricsMailet.java

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 * regarding copyright ownership.  The ASF licenses this file   *
 * to you under the Apache License, Version 2.0 (the            *
 * "License"); you may not use this file except in compliance   *
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package org.apache.james.transport.mailets;

import javax.inject.Inject;
import javax.mail.MessagingException;

import org.apache.james.metrics.api.Metric;
import org.apache.james.metrics.api.MetricFactory;
import org.apache.mailet.Mail;
import org.apache.mailet.base.GenericMailet;

import com.google.common.base.Preconditions;

/**
 * This Metrics mailet increments a counter on every incoming emails.
 *
 * This counter is accessible via JMX.
 *
 * Example :
 *
 * <mailet match="all" class="MetricsMailet">
 *     <metricName>relayDenied</metricName>
 * </mailet>
 *
 * Will increment a counter relay denied
 */
public class MetricsMailet extends GenericMailet {
    public static final String METRIC_NAME = "metricName";

    private final MetricFactory metricFactory;
    private Metric metric;

    @Inject
    public MetricsMailet(MetricFactory metricFactory) {
        this.metricFactory = metricFactory;
    }

    @Override
    public void init() throws MessagingException {
        String metricName = getInitParameter(METRIC_NAME);
        init(metricName);
    }

    private void init(String metricName) {
        Preconditions.checkNotNull(metricName);
        metric = metricFactory.generate(metricName);
    }

    @Override
    public void service(Mail mail) throws MessagingException {
        metric.increment();
    }

    @Override
    public String getMailetInfo() {
        return "Metrics mailet";
    }
}