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Added support for schema evolution for the Avro generic serializer
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src/java/voldemort/serialization/avro/versioned/AvroVersionedGenericSerializer.java
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| /* | ||
| * Copyright 2011 LinkedIn, Inc | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); you may not | ||
| * use this file except in compliance with the License. You may obtain a copy of | ||
| * the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| * License for the specific language governing permissions and limitations under | ||
| * the License. | ||
| */ | ||
| package voldemort.serialization.avro.versioned; | ||
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| import java.io.ByteArrayOutputStream; | ||
| import java.io.IOException; | ||
| import java.util.Map; | ||
| import java.util.SortedMap; | ||
| import java.util.TreeMap; | ||
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| import org.apache.avro.Schema; | ||
| import org.apache.avro.generic.GenericDatumReader; | ||
| import org.apache.avro.generic.GenericDatumWriter; | ||
| import org.apache.avro.io.BinaryEncoder; | ||
| import org.apache.avro.io.Decoder; | ||
| import org.apache.avro.io.DecoderFactory; | ||
| import org.apache.avro.io.Encoder; | ||
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| import voldemort.serialization.SerializationException; | ||
| import voldemort.serialization.SerializationUtils; | ||
| import voldemort.serialization.Serializer; | ||
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| /** | ||
| * Avro serializer that uses the generic representation for Avro data. This | ||
| * representation is best for applications which deal with dynamic data, whose | ||
| * schemas are not known until runtime. | ||
| * | ||
| */ | ||
| public class AvroVersionedGenericSerializer implements Serializer<Object> { | ||
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| private final SortedMap<Integer, String> typeDefVersions; | ||
| private final Integer newestVersion; | ||
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| // reader's schema | ||
| private final Schema typeDef; | ||
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| /** | ||
| * Constructor accepting the schema definition as a JSON string. | ||
| * | ||
| * @param schema a serialized JSON object representing a Avro schema. | ||
| */ | ||
| public AvroVersionedGenericSerializer(String schema) { | ||
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| this.typeDefVersions = new TreeMap<Integer, String>(); | ||
| this.typeDefVersions.put(0, schema); | ||
| newestVersion = typeDefVersions.lastKey(); | ||
| typeDef = Schema.parse(typeDefVersions.get(newestVersion)); | ||
| } | ||
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| public AvroVersionedGenericSerializer(Map<Integer, String> typeDefVersions) { | ||
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| this.typeDefVersions = new TreeMap<Integer, String>(typeDefVersions); | ||
| newestVersion = this.typeDefVersions.lastKey(); | ||
| typeDef = Schema.parse(typeDefVersions.get(newestVersion)); | ||
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| } | ||
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| public byte[] toBytes(Object object) { | ||
| ByteArrayOutputStream output = new ByteArrayOutputStream(); | ||
| Encoder encoder = new BinaryEncoder(output); | ||
| GenericDatumWriter<Object> datumWriter = null; | ||
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| output.write(newestVersion.byteValue()); | ||
| try { | ||
| datumWriter = new GenericDatumWriter<Object>(typeDef); | ||
| datumWriter.write(object, encoder); | ||
| encoder.flush(); | ||
| } catch(IOException e) { | ||
| throw new SerializationException(e); | ||
| } finally { | ||
| SerializationUtils.close(output); | ||
| } | ||
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| byte version = newestVersion.byteValue(); | ||
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| return output.toByteArray(); | ||
| } | ||
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| public Object toObject(byte[] bytes) { | ||
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| Integer version = Integer.valueOf(bytes[0]); | ||
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| Schema typeDefWriter = Schema.parse(typeDefVersions.get(version)); | ||
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| byte[] dataBytes = new byte[bytes.length - 1]; | ||
| System.arraycopy(bytes, 1, dataBytes, 0, bytes.length - 1); | ||
| Decoder decoder = DecoderFactory.defaultFactory().createBinaryDecoder(dataBytes, null); | ||
| GenericDatumReader<Object> reader = null; | ||
| try { | ||
| reader = new GenericDatumReader<Object>(typeDefWriter, typeDef); | ||
| // writer's schema | ||
| reader.setSchema(typeDefWriter); | ||
| // Reader's schema | ||
| reader.setExpected(typeDef); | ||
| return reader.read(null, decoder); | ||
| } catch(IOException e) { | ||
| throw new SerializationException(e); | ||
| } | ||
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| } | ||
| } |