org.kiji.rest.serializers.AvroToJsonStringSerializer.java Source code

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Here is the source code for org.kiji.rest.serializers.AvroToJsonStringSerializer.java

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/**
 * (c) Copyright 2013 WibiData, Inc.
 *
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * 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 org.kiji.rest.serializers;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.Charset;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;

import org.apache.avro.AvroRuntimeException;
import org.apache.avro.generic.GenericContainer;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.io.JsonEncoder;
import org.apache.avro.specific.SpecificDatumWriter;
import org.apache.avro.specific.SpecificRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Avro's specific types don't seem to serialize properly so this class provides
 * the necessary hook to convert an Avro SpecificRecordBase to a Json string literal meant to
 * be embedded in another JSON object sent back to the client.
 *
 */
public class AvroToJsonStringSerializer extends JsonSerializer<GenericContainer> {

    private static final Logger LOG = LoggerFactory.getLogger(AvroToJsonStringSerializer.class);

    /**
     * {@inheritDoc}
     */
    @Override
    public void serialize(GenericContainer record, JsonGenerator generator, SerializerProvider provider)
            throws IOException {
        try {
            generator.writeObject(getJsonNode(record));
        } catch (AvroRuntimeException are) {
            LOG.error("Error writing Avro record ", are);
            throw are;
        }
    }

    /**
     * Returns an encoded JSON string for the given Avro object.
     *
     * @param record is the record to encode
     * @return the JSON string representing this Avro object.
     *
     * @throws IOException if there is an error.
     */
    public static String getJsonString(GenericContainer record) throws IOException {
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        JsonEncoder encoder = EncoderFactory.get().jsonEncoder(record.getSchema(), os);
        DatumWriter<GenericContainer> writer = new GenericDatumWriter<GenericContainer>();
        if (record instanceof SpecificRecord) {
            writer = new SpecificDatumWriter<GenericContainer>();
        }

        writer.setSchema(record.getSchema());
        writer.write(record, encoder);
        encoder.flush();
        String jsonString = new String(os.toByteArray(), Charset.forName("UTF-8"));
        os.close();
        return jsonString;
    }

    /**
     * Returns an encoded JSON object for the given Avro object.
     *
     * @param record is the record to encode
     * @return the JSON object representing this Avro object.
     *
     * @throws IOException if there is an error.
     */
    public static JsonNode getJsonNode(GenericContainer record) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readTree(getJsonString(record));
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Class<GenericContainer> handledType() {
        return GenericContainer.class;
    }
}