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    
019    package org.apache.hadoop.io.serializer;
020    
021    import java.io.DataInputStream;
022    import java.io.DataOutputStream;
023    import java.io.IOException;
024    import java.io.InputStream;
025    import java.io.OutputStream;
026    import java.util.Map;
027    
028    import org.apache.hadoop.classification.InterfaceAudience;
029    import org.apache.hadoop.classification.InterfaceStability;
030    import org.apache.hadoop.conf.Configuration;
031    import org.apache.hadoop.conf.Configured;
032    import org.apache.hadoop.io.Writable;
033    import org.apache.hadoop.util.ReflectionUtils;
034    
035    /**
036     * A {@link Serialization} for {@link Writable}s that delegates to
037     * {@link Writable#write(java.io.DataOutput)} and
038     * {@link Writable#readFields(java.io.DataInput)}.
039     */
040    @InterfaceAudience.Public
041    @InterfaceStability.Evolving
042    public class WritableSerialization extends Configured
043            implements Serialization<Writable> {
044      static class WritableDeserializer extends Configured
045            implements Deserializer<Writable> {
046    
047        private Class<?> writableClass;
048        private DataInputStream dataIn;
049        
050        public WritableDeserializer(Configuration conf, Class<?> c) {
051          setConf(conf);
052          this.writableClass = c;
053        }
054        
055        @Override
056        public void open(InputStream in) {
057          if (in instanceof DataInputStream) {
058            dataIn = (DataInputStream) in;
059          } else {
060            dataIn = new DataInputStream(in);
061          }
062        }
063        
064        @Override
065        public Writable deserialize(Writable w) throws IOException {
066          Writable writable;
067          if (w == null) {
068            writable 
069              = (Writable) ReflectionUtils.newInstance(writableClass, getConf());
070          } else {
071            writable = w;
072          }
073          writable.readFields(dataIn);
074          return writable;
075        }
076    
077        @Override
078        public void close() throws IOException {
079          dataIn.close();
080        }
081        
082      }
083      
084      static class WritableSerializer extends Configured implements
085            Serializer<Writable> {
086        
087        private DataOutputStream dataOut;
088        
089        @Override
090        public void open(OutputStream out) {
091          if (out instanceof DataOutputStream) {
092            dataOut = (DataOutputStream) out;
093          } else {
094            dataOut = new DataOutputStream(out);
095          }
096        }
097    
098        @Override
099        public void serialize(Writable w) throws IOException {
100          w.write(dataOut);
101        }
102    
103        @Override
104        public void close() throws IOException {
105          dataOut.close();
106        }
107    
108      }
109    
110      @InterfaceAudience.Private
111      @Override
112      public boolean accept(Class<?> c) {
113        return Writable.class.isAssignableFrom(c);
114      }
115    
116      @InterfaceAudience.Private
117      @Override
118      public Serializer<Writable> getSerializer(Class<Writable> c) {
119        return new WritableSerializer();
120      }
121      
122      @InterfaceAudience.Private
123      @Override
124      public Deserializer<Writable> getDeserializer(Class<Writable> c) {
125        return new WritableDeserializer(getConf(), c);
126      }
127    
128    }