com.hpcloud.mon.common.model.metric.Metrics.java Source code

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Here is the source code for com.hpcloud.mon.common.model.metric.Metrics.java

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/*
 * Copyright (c) 2014 Hewlett-Packard Development Company, L.P.
 *
 * 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.hpcloud.mon.common.model.metric;

import java.io.IOException;
import java.util.Map;

import org.apache.commons.lang3.StringEscapeUtils;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.hpcloud.util.Exceptions;

/**
 * Utilities for working with Metrics.
 */
public final class Metrics {
    static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();

    static {
        OBJECT_MAPPER.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
        SimpleModule module = new SimpleModule();
        module.addSerializer(new MetricSerializer());
        OBJECT_MAPPER.registerModule(module);
    }

    /** Metric serializer */
    private static class MetricSerializer extends JsonSerializer<Metric> {
        @Override
        public Class<Metric> handledType() {
            return Metric.class;
        }

        public void serialize(Metric value, JsonGenerator jgen, SerializerProvider provider)
                throws IOException, JsonProcessingException {
            jgen.writeStartObject();

            jgen.writeStringField("name", value.name);
            if (value.dimensions != null && !value.dimensions.isEmpty())
                jgen.writeObjectField("dimensions", value.dimensions);
            jgen.writeNumberField("timestamp", value.timestamp);

            if (value.timeValues == null)
                jgen.writeNumberField("value", value.value);
            else {
                jgen.writeArrayFieldStart("time_values");
                for (double[] timeValue : value.timeValues) {
                    jgen.writeStartArray();
                    jgen.writeNumber((long) timeValue[0]); // Write timestamp as a long
                    jgen.writeNumber(timeValue[1]);
                    jgen.writeEndArray();
                }
                jgen.writeEndArray();
            }

            jgen.writeEndObject();
        }
    }

    private Metrics() {
    }

    /**
     * Returns the Metric for the {@code metricJson}.
     * 
     * @throws RuntimeException if an error occurs while parsing {@code metricJson}
     */
    public static Metric fromJson(byte[] metricJson) {
        try {
            String jsonStr = StringEscapeUtils.unescapeJava(new String(metricJson, "UTF-8"));
            return OBJECT_MAPPER.readValue(jsonStr, Metric.class);
        } catch (Exception e) {
            throw Exceptions.uncheck(e, "Failed to parse metric json: %s", new String(metricJson));
        }
    }

    /**
     * Returns the JSON representation of the {@code metric} else null if it could not be converted to
     * JSON.
     */
    public static String toJson(Metric metric) {
        try {
            return OBJECT_MAPPER.writeValueAsString(metric);
        } catch (JsonProcessingException e) {
            return null;
        }
    }

    /**
     * Returns a metric for the {@code metric} and {@code dimensions}.
     */
    public static Metric of(Metric metric, Map<String, String> dimensions) {
        return metric.timeValues == null ? new Metric(metric.name, dimensions, metric.timestamp, metric.value)
                : new Metric(metric.name, dimensions, metric.timestamp, metric.timeValues);
    }
}