001    /**
002     * Copyright (c) 2010 Yahoo! Inc. All rights reserved.
003     * Licensed under the Apache License, Version 2.0 (the "License");
004     * you may not use this file except in compliance with the License.
005     * You may obtain a copy of the License at
006     *
007     *   http://www.apache.org/licenses/LICENSE-2.0
008     *
009     *  Unless required by applicable law or agreed to in writing, software
010     *  distributed under the License is distributed on an "AS IS" BASIS,
011     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012     *  See the License for the specific language governing permissions and
013     *  limitations under the License. See accompanying LICENSE file.
014     */
015    package org.apache.oozie.util;
016    
017    import org.apache.hadoop.io.Writable;
018    import org.apache.hadoop.util.ReflectionUtils;
019    
020    import java.io.ByteArrayInputStream;
021    import java.io.ByteArrayOutputStream;
022    import java.io.DataInputStream;
023    import java.io.DataOutputStream;
024    import java.io.IOException;
025    import java.io.DataOutput;
026    import java.io.DataInput;
027    
028    /**
029     * Utility class to write/read Hadoop writables to/from a byte array.
030     */
031    public class WritableUtils {
032    
033        /**
034         * Write a writable to a byte array.
035         *
036         * @param writable writable to write.
037         * @return array containing the serialized writable.
038         */
039        public static byte[] toByteArray(Writable writable) {
040            try {
041                ByteArrayOutputStream baos = new ByteArrayOutputStream();
042                DataOutputStream daos = new DataOutputStream(baos);
043                writable.write(daos);
044                daos.close();
045                return baos.toByteArray();
046            }
047            catch (IOException ex) {
048                throw new RuntimeException(ex);
049            }
050        }
051    
052        /**
053         * Read a writable from a byte array.
054         *
055         * @param array byte array with the serialized writable.
056         * @param clazz writable class.
057         * @return writable deserialized from the byte array.
058         */
059        @SuppressWarnings("unchecked")
060        public static <T extends Writable> T fromByteArray(byte[] array, Class<T> clazz) {
061            try {
062                T o = (T) ReflectionUtils.newInstance(clazz, null);
063                o.readFields(new DataInputStream(new ByteArrayInputStream(array)));
064                return o;
065            }
066            catch (IOException ex) {
067                throw new RuntimeException(ex);
068            }
069        }
070    
071        private static final String NULL = "||";
072    
073        /**
074         * Write a string to a data output supporting <code>null</code> values. <p/> It uses the '||' token to represent
075         * <code>null</code>.
076         *
077         * @param dataOutput data output.
078         * @param str string to write.
079         * @throws IOException thrown if the string could not be written.
080         */
081        public static void writeStr(DataOutput dataOutput, String str) throws IOException {
082            str = (str != null) ? str : NULL;
083            dataOutput.writeUTF(str);
084        }
085    
086        /**
087         * Read a string from a data input supporting <code>null</code> values. <p/> It uses the '||' token to represent
088         * <code>null</code>.
089         *
090         * @param dataInput data input.
091         * @return read string, <code>null</code> if the '||' token was read.
092         * @throws IOException thrown if the string could not be read.
093         */
094        public static String readStr(DataInput dataInput) throws IOException {
095            String str = dataInput.readUTF();
096            return (str.equals(NULL)) ? null : str;
097        }
098    }