co.cask.cdap.api.dataset.lib.partitioned.ComparableCodec.java Source code

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Here is the source code for co.cask.cdap.api.dataset.lib.partitioned.ComparableCodec.java

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/*
 * Copyright  2016 Cask Data, Inc.
 *
 * 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 co.cask.cdap.api.dataset.lib.partitioned;

import com.google.gson.JsonArray;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonElement;
import com.google.gson.JsonSerializationContext;

import javax.annotation.Nullable;

/**
 * Responsible for serialization and deserialization of {@link Comparable}.
 */
public class ComparableCodec {

    @Nullable
    protected JsonElement serializeComparable(@Nullable Comparable comparable,
            JsonSerializationContext jsonSerializationContext) {
        if (comparable == null) {
            return null;
        }
        JsonArray jsonArray = new JsonArray();
        jsonArray.add(jsonSerializationContext.serialize(comparable.getClass().getName()));
        jsonArray.add(jsonSerializationContext.serialize(comparable));
        return jsonArray;
    }

    @Nullable
    protected Comparable deserializeComparable(@Nullable JsonElement comparableJson,
            JsonDeserializationContext jsonDeserializationContext) {
        if (comparableJson == null) {
            return null;
        }
        JsonArray jsonArray = comparableJson.getAsJsonArray();
        // the classname is serialized as the first element, the value is serialized as the second
        Class<? extends Comparable> comparableClass = forName(jsonArray.get(0).getAsString());
        return jsonDeserializationContext.deserialize(jsonArray.get(1), comparableClass);
    }

    @SuppressWarnings("unchecked")
    private Class<? extends Comparable> forName(String className) {
        try {
            // we know that the class is a Comparable because all partition keys are of type Comparable
            return (Class<? extends Comparable>) Class.forName(className);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }
}