org.wikidata.query.rdf.tool.change.JsonDeserializer Maven / Gradle / Ivy

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Tools to sync Wikibase to RDF stores. Also contains overall integration tests that rely on everything else.

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package org.wikidata.query.rdf.tool.change;

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.wikidata.query.rdf.tool.MapperUtils.getObjectMapper;

import java.io.IOException;
import java.util.Map;

import org.apache.kafka.common.serialization.Deserializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * Deserializer for Kafka stream objects from JSON.
 * This class allows to deserialize a family of related classes.
 *
 * @param  Type to be deserialized into.
 */
public class JsonDeserializer implements Deserializer {

    private static final Logger logger = LoggerFactory.getLogger(JsonDeserializer.class);

    private final ObjectMapper mapper = getObjectMapper();

    private final Map> topicToClass;

    public JsonDeserializer(Map> topicToClass) {
        this.topicToClass = topicToClass;
    }

    @Override
    public void configure(Map configs, boolean isKey) {
        // all configuration is through constructor
    }

    @Override
    public T deserialize(String topic, byte[] data) {
        if (data == null) return null;

        try {
            return mapper.readValue(data, topicToClass.get(topic));
        } catch (IOException e) {
            String dataString = new String(data, UTF_8);
            logger.warn("Data in topic {} cannot be deserialized [{}].", topic, dataString, e);
            return null;
        }
    }

    @Override
    public void close() {
        // NOOP
    }
}