external/storm-cassandra/src/main/java/org/apache/storm/cassandra/trident/state/SerializedStateMapper.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information 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 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 org.apache.storm.cassandra.trident.state;

import java.nio.ByteBuffer;
import java.util.List;
import org.apache.storm.trident.state.Serializer;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Values;

public class SerializedStateMapper<T> implements StateMapper<T> {

    private final Fields stateFields;
    private final Serializer<T> serializer;

    public SerializedStateMapper(String fieldName, Serializer<T> serializer) {
        this.stateFields = new Fields(fieldName);
        this.serializer = serializer;
    }

    @Override
    public Fields getStateFields() {
        return stateFields;
    }

    @Override
    public Values toValues(T value) {
        byte[] serialized = serializer.serialize(value);
        return new Values(ByteBuffer.wrap(serialized));
    }

    @Override
    public T fromValues(List<Values> values) {
        if (values.size() == 0) {
            return null;
        } else if (values.size() == 1) {
            ByteBuffer bytes = (ByteBuffer) values.get(0).get(0);
            return serializer.deserialize(bytes.array());
        } else {
            throw new IllegalArgumentException("Can only convert single values, " + values.size() + " encountered");
        }
    }

    @Override
    public String toString() {
        return String.format("{type: %s, fields: %s, serializer: %s}", this.getClass().getSimpleName(), stateFields, serializer);
    }
}