什么是JavaInPutdStream中的“classRecordClass”？

Question

我试图使用下面的API与Kafka火花流。我必须用spark流avro序列化数据，数据位于Kafka中。

static <K,V,KD extends kafka.serializer.Decoder<K>,VD extends kafka.serializer.Decoder<V>,R> 
    JavaInputDStream<R> createDirectStream(JavaStreamingContext jssc, Class<K> keyClass, Class<V> valueClass, Class<KD> keyDecoderClass, Class<VD> valueDecoderClass, Class<R> recordClass, java.util.Map<String,String> kafkaParams, java.util.Map<kafka.common.TopicAndPartition,Long> fromOffsets, Function<kafka.message.MessageAndMetadata<K,V>,R> messageHandler)
    :: Experimental :: Create an input stream that directly pulls messages from Kafka Brokers without using any receiver.

JavaInputDStream<byte[]> directKafkaStream = KafkaUtils.createDirectStream(jsc, String.class, byte[].class,
        StringDecoder.class, DefaultDecoder.class, byte[].class, kafkaParams, topicMap,
        (Function<MessageAndMetadata<String, String>, String>) MessageAndMetadata::message);

错误：未解决的编译问题：KafkaUtils类型中的方法createDirectStream(JavaStreamingContext,Class,Class,Class,Class,Class,Class,Class,Class,Class,Map,Map,Function,r>)不适用于参数(JavaStreamingContext,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,Class,

Answer 1

试试这个。

 JavaInputDStream<byte[]> directKafkaStream = KafkaUtils.createDirectStream(jssc, String.class, byte[].class,
                StringDecoder.class, DefaultDecoder.class, byte[].class, kafkaParams, fromOffset,
                (Function<MessageAndMetadata<String, byte[]>, byte[]>) MessageAndMetadata::message);

这里有一篇为Kafka，阿夫罗和Spark写的文章。