asterix-metadata/src/main/java/org/apache/asterix/metadata/api/IMetadataEntityTupleTranslator.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.asterix.metadata.api;

import java.io.IOException;

import org.apache.asterix.metadata.MetadataException;
import org.apache.hyracks.dataflow.common.data.accessors.ITupleReference;

/**
 * Interface for translating the representation of metadata entities (datasets,
 * types, etc.) from their Java object representation to a serialized
 * representation in a Hyracks tuple, and vice versa. Implementations of this
 * interface are intended to be used within an IMetadataNode.
 */
public interface IMetadataEntityTupleTranslator<T> {

    /**
     * Transforms a metadata entity of type T from a given tuple to a Java
     * object (deserializing the appropriate field(s) in the tuple as
     * necessary).
     * 
     * @param tuple
     *            Tuple containing a serialized representation of a metadata
     *            entity of type T.
     * @return A new instance of a metadata entity of type T.
     * @throws MetadataException
     * @throws IOException
     */
    public T getMetadataEntityFromTuple(ITupleReference tuple) throws MetadataException, IOException;

    /**
     * Serializes the given metadata entity of type T into an appropriate tuple
     * representation (i.e., some number of fields containing bytes).
     * 
     * @param metadataEntity
     *            Metadata entity to be written into a tuple.
     * @throws IOException
     */
    public ITupleReference getTupleFromMetadataEntity(T metadataEntity) throws MetadataException, IOException;
}