从JDBC Connector反序列化avro kafka消息时出错

Question

我正在尝试使用汇合的kafka连接功能来收听我发布的主题。但是，我无法对其进行反序列化。我相信它的avro序列化但无法找到正确的解串器。

消息如下所示在控制台主题中

null    {"c1":{"int":10},"c2":{"string":"foo"},"create_ts":1552598863000,"update_ts":1552598863000}

下面是解串器

public class AvroDeserializer<T extends SpecificRecordBase> implements Deserializer<T> {

    private static final Logger LOGGER = LoggerFactory.getLogger(AvroDeserializer.class);

    protected final Class<T> targetType;

    public AvroDeserializer(Class<T> targetType) {
        this.targetType = targetType;
    }

    @Override
    public void close() {
        // No-op
    }

    @Override
    public void configure(Map<String, ?> arg0, boolean arg1) {
        // No-op
    }

    @SuppressWarnings("unchecked")
    @Override
    public T deserialize(String topic, byte[] data) {
        try {
            T result = null;

            if (data != null) {
                LOGGER.debug("data='{}'", DatatypeConverter.printHexBinary(data));

                DatumReader<GenericRecord> datumReader =
                        new SpecificDatumReader<>(targetType.newInstance().getSchema());
                Decoder decoder = DecoderFactory.get().binaryDecoder(data, null);

                result = (T) datumReader.read(null, decoder);
                LOGGER.debug("deserialized data='{}'", result);
            }
            return result;
        } catch (Exception ex) {
            throw new SerializationException(
                    "Can't deserialize data '" + Arrays.toString(data) + "' from topic '" + topic + "'", ex);
        }
    }
}

例外

org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition mysql-foobar-0 at offset 10. If needed, please seek past the record to continue consumption.
Caused by: org.apache.kafka.common.errors.SerializationException: Can't deserialize data '[0, 0, 0, 0, 21, 2, 20, 2, 6, 102, 111, 111, -80, -78, -44, -31, -81, 90, -80, -78, -44, -31, -81, 90]' from topic 'mysql-foobar'
Caused by: java.lang.InstantiationException: null
    at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48) ~[na:1.8.0_131]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_131]
    at java.lang.Class.newInstance(Class.java:442) ~[na:1.8.0_131]
    at com.spring.kafkaexample.springbootkafkaconsumer.config.AvroDeserializer.deserialize(AvroDeserializer.java:48) ~[classes/:na]
    at com.spring.kafkaexample.springbootkafkaconsumer.config.AvroDeserializer.deserialize(AvroDeserializer.java:18) ~[classes/:na]

Answer 1

如下所示在控制台主题中

目前尚不清楚你是使用kafka-avro-console-consumer还是仅仅使用kafka-console-consumer。了解您的数据是否为Avro的方法是查看Producer / connector配置。

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但是，没有必要编写自己的反序列化器。另外，Confluent不会使用您的代码所具有的Avro架构+消息约定（因此您会收到该错误）。您需要首先从架构注册表中查找架构。

添加Confluent Maven仓库

<repositories>

  <repository>
    <id>confluent</id>
    <url>https://packages.confluent.io/maven/</url>
  </repository>

</repositories>

然后添加Confluent序列化程序依赖项

<dependency>
  <groupId>io.confluent</groupId>
  <artifactId>kafka-avro-serializer</artifactId>
  <version>${confluent.version}</version>
</dependency>

然后import io.confluent.kafka.serializers.KafkaAvroDeserializer，或在您的消费者配置中使用该类

https://docs.confluent.io/current/clients/install.html#java

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或者，您可以将MySQL连接器切换为不使用Avro Converter