gobblin.converter.avro.AvroToJsonStringConverterBase.java Source code

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Here is the source code for gobblin.converter.avro.AvroToJsonStringConverterBase.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 gobblin.converter.avro;

import java.io.IOException;
import java.util.Collections;

import org.apache.avro.Schema;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.Encoder;
import org.apache.avro.io.EncoderFactory;
import org.apache.commons.io.output.ByteArrayOutputStream;

import com.google.common.base.Charsets;
import com.google.common.collect.Lists;

import gobblin.configuration.WorkUnitState;
import gobblin.converter.Converter;
import gobblin.converter.DataConversionException;
import gobblin.converter.SchemaConversionException;

/**
 * Converts an Avro record to a json string.
 */
public abstract class AvroToJsonStringConverterBase<T> extends Converter<Schema, String, GenericRecord, T> {

    private Schema schema;

    private final ThreadLocal<Serializer> serializer = new ThreadLocal<Serializer>() {
        @Override
        protected Serializer initialValue() {
            return new Serializer(AvroToJsonStringConverterBase.this.schema);
        }
    };

    private static class Serializer {

        private final Encoder encoder;
        private final GenericDatumWriter<GenericRecord> writer;
        private final ByteArrayOutputStream outputStream;

        public Serializer(Schema schema) {
            try {
                this.writer = new GenericDatumWriter<>(schema);
                this.outputStream = new ByteArrayOutputStream();
                this.encoder = EncoderFactory.get().jsonEncoder(schema, this.outputStream);
            } catch (IOException ioe) {
                throw new RuntimeException("Could not initialize avro json encoder.");
            }
        }

        public byte[] serialize(GenericRecord record) throws IOException {
            this.outputStream.reset();
            this.writer.write(record, this.encoder);
            this.encoder.flush();
            return this.outputStream.toByteArray();
        }
    }

    @Override
    public String convertSchema(Schema inputSchema, WorkUnitState workUnit) throws SchemaConversionException {
        this.schema = inputSchema;
        return this.schema.toString();
    }

    @Override
    public Iterable<T> convertRecord(String outputSchema, GenericRecord inputRecord, WorkUnitState workUnit)
            throws DataConversionException {
        try {
            byte[] utf8Bytes = this.serializer.get().serialize(inputRecord);
            return Collections.singleton(processUtf8Bytes(utf8Bytes));
        } catch (IOException ioe) {
            throw new DataConversionException(ioe);
        }
    }

    protected abstract T processUtf8Bytes(byte[] utf8Bytes);
}