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 */
018package org.apache.oozie.util;
019
020import org.apache.hadoop.io.Writable;
021import org.apache.hadoop.util.ReflectionUtils;
022
023import java.io.ByteArrayInputStream;
024import java.io.ByteArrayOutputStream;
025import java.io.DataInputStream;
026import java.io.DataOutputStream;
027import java.io.IOException;
028import java.io.DataOutput;
029import java.io.DataInput;
030
031/**
032 * Utility class to write/read Hadoop writables to/from a byte array.
033 */
034public class WritableUtils {
035
036    /**
037     * Write a writable to a byte array.
038     *
039     * @param writable writable to write.
040     * @return array containing the serialized writable.
041     */
042    public static byte[] toByteArray(Writable writable) {
043        try {
044            ByteArrayOutputStream baos = new ByteArrayOutputStream();
045            DataOutputStream daos = new DataOutputStream(baos);
046            writable.write(daos);
047            daos.close();
048            return baos.toByteArray();
049        }
050        catch (IOException ex) {
051            throw new RuntimeException(ex);
052        }
053    }
054
055    /**
056     * Read a writable from a byte array.
057     *
058     * @param array byte array with the serialized writable.
059     * @param clazz writable class.
060     * @return writable deserialized from the byte array.
061     */
062    @SuppressWarnings("unchecked")
063    public static <T extends Writable> T fromByteArray(byte[] array, Class<T> clazz) {
064        try {
065            T o = (T) ReflectionUtils.newInstance(clazz, null);
066            o.readFields(new DataInputStream(new ByteArrayInputStream(array)));
067            return o;
068        }
069        catch (IOException ex) {
070            throw new RuntimeException(ex);
071        }
072    }
073
074    private static final String NULL = "||";
075
076    /**
077     * Write a string to a data output supporting <code>null</code> values. <p/> It uses the '||' token to represent
078     * <code>null</code>.
079     *
080     * @param dataOutput data output.
081     * @param str string to write.
082     * @throws IOException thrown if the string could not be written.
083     */
084    public static void writeStr(DataOutput dataOutput, String str) throws IOException {
085        str = (str != null) ? str : NULL;
086        dataOutput.writeUTF(str);
087    }
088
089    /**
090     * Read a string from a data input supporting <code>null</code> values. <p/> It uses the '||' token to represent
091     * <code>null</code>.
092     *
093     * @param dataInput data input.
094     * @return read string, <code>null</code> if the '||' token was read.
095     * @throws IOException thrown if the string could not be read.
096     */
097    public static String readStr(DataInput dataInput) throws IOException {
098        String str = dataInput.readUTF();
099        return (str.equals(NULL)) ? null : str;
100    }
101}