Source code

001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *      http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.oozie.util;
020
021import org.apache.hadoop.io.Writable;
022import org.apache.hadoop.util.ReflectionUtils;
023
024import java.io.ByteArrayInputStream;
025import java.io.ByteArrayOutputStream;
026import java.io.DataInputStream;
027import java.io.DataOutputStream;
028import java.io.IOException;
029import java.io.DataOutput;
030import java.io.DataInput;
031
032/**
033 * Utility class to write/read Hadoop writables to/from a byte array.
034 */
035public class WritableUtils {
036
037    /**
038     * Write a writable to a byte array.
039     *
040     * @param writable writable to write.
041     * @return array containing the serialized writable.
042     */
043    public static byte[] toByteArray(Writable writable) {
044        try {
045            ByteArrayOutputStream baos = new ByteArrayOutputStream();
046            DataOutputStream daos = new DataOutputStream(baos);
047            writable.write(daos);
048            daos.close();
049            return baos.toByteArray();
050        }
051        catch (IOException ex) {
052            throw new RuntimeException(ex);
053        }
054    }
055
056    /**
057     * Read a writable from a byte array.
058     *
059     * @param array byte array with the serialized writable.
060     * @param clazz writable class.
061     * @return writable deserialized from the byte array.
062     */
063    @SuppressWarnings("unchecked")
064    public static <T extends Writable> T fromByteArray(byte[] array, Class<T> clazz) {
065        try {
066            T o = (T) ReflectionUtils.newInstance(clazz, null);
067            o.readFields(new DataInputStream(new ByteArrayInputStream(array)));
068            return o;
069        }
070        catch (IOException ex) {
071            throw new RuntimeException(ex);
072        }
073    }
074
075    private static final String NULL = "||";
076
077    /**
078     * Write a string to a data output supporting <code>null</code> values. <p/> It uses the '||' token to represent
079     * <code>null</code>.
080     *
081     * @param dataOutput data output.
082     * @param str string to write.
083     * @throws IOException thrown if the string could not be written.
084     */
085    public static void writeStr(DataOutput dataOutput, String str) throws IOException {
086        str = (str != null) ? str : NULL;
087        dataOutput.writeUTF(str);
088    }
089
090    /**
091     * Read a string from a data input supporting <code>null</code> values. <p/> It uses the '||' token to represent
092     * <code>null</code>.
093     *
094     * @param dataInput data input.
095     * @return read string, <code>null</code> if the '||' token was read.
096     * @throws IOException thrown if the string could not be read.
097     */
098    public static String readStr(DataInput dataInput) throws IOException {
099        String str = dataInput.readUTF();
100        return (str.equals(NULL)) ? null : str;
101    }
102}