Question

为什么以下行与KafkaUtils.createStream

val reciver = KafkaUtils.createStream[String, String , StringDecoder, StringDecoder](ssc, kafkaParams, topics).map(_._2)

给我error: overloaded method value createStream with alternatives:？

error: overloaded method value createStream with alternatives:
(jssc: org.apache.spark.streaming.api.java.JavaStreamingContext,keyTypeClass: Class[String],valueTypeClass: Class[String],keyDecoderClass: Class[kafka.serializer.StringDecoder],valueDecoderClass: Class[kafka.serializer.StringDecoder],kafkaParams: java.util.Map[String,String],topics: java.util.Map[String,Integer],storageLevel: org.apache.spark.storage.StorageLevel)org.apache.spark.streaming.api.java.JavaPairReceiverInputDStream[String,String] <and> (ssc: org.apache.spark.streaming.StreamingContext,kafkaParams: scala.collection.immutable.Map[String,String],topics: scala.collection.immutable.Map[String,Int],storageLevel: org.apache.spark.storage.StorageLevel)(implicit evidence$1: scala.reflect.ClassTag[String], implicit evidence$2: scala.reflect.ClassTag[String], implicit evidence$3: scala.reflect.ClassTag[kafka.serializer.StringDecoder], implicit evidence$4: scala.reflect.ClassTag[kafka.serializer.StringDecoder])org.apache.spark.streaming.dstream.ReceiverInputDStream[(String, String)]
 cannot be applied to (org.apache.spark.streaming.StreamingContext, scala.collection.immutable.Map[String,String], scala.collection.immutable.Set[String])
       KafkaUtils.createStream(ssc, kafkaParams, topics)
                  ^

Answer 1

无法应用于（org.apache.spark.streaming.StreamingContext，scala.collection.mutable.Map [String，String]，scala.collection.immutable.Set [String]）

请注意与KafkaUtils.createStream支持的类型不匹配的类型。

您似乎最接近以下内容：

createStream[K, V, U <: Decoder[_], T <: Decoder[_]](
    ssc: StreamingContext,
    kafkaParams: Map[String, String],
    topics: Map[String, Int],
    storageLevel: StorageLevel)(/** implicits removed */): ReceiverInputDStream[(K, V)]

且您的topics类型为Set，而非Map（！）

使用官方KafkaWordCount示例获取支持。

为什么KafkaUtils.createStream失败并出现“错误：重载方法值createStream with alternatives”？

1 个答案: