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 package org.apache.oozie.util;
019
020 import org.apache.hadoop.io.Writable;
021 import org.apache.hadoop.util.ReflectionUtils;
022
023 import java.io.ByteArrayInputStream;
024 import java.io.ByteArrayOutputStream;
025 import java.io.DataInputStream;
026 import java.io.DataOutputStream;
027 import java.io.IOException;
028 import java.io.DataOutput;
029 import java.io.DataInput;
030
031 /**
032 * Utility class to write/read Hadoop writables to/from a byte array.
033 */
034 public 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 }