Scala writeStream()正在批处理数据中打印空值,即使我通过writeStream()在kafka中提供了正确的json数据
我试图使用模式转换json并将值打印到控制台,但writeStream()在所有列中打印空值,即使我提供了正确的数据 我给卡夫卡主题的数据Scala writeStream()正在批处理数据中打印空值,即使我通过writeStream()在kafka中提供了正确的json数据,scala,apache-spark,apache-kafka,apache-spark-sql,spark-structured-streaming,Scala,Apache Spark,Apache Kafka,Apache Spark Sql,Spark Structured Streaming,我试图使用模式转换json并将值打印到控制台,但writeStream()在所有列中打印空值,即使我提供了正确的数据 我给卡夫卡主题的数据 {"stock":"SEE","buy":12,"sell":15,"profit":3,quantity:27,"loss":0,"gender":"M"} {"stock":"SEE","buy":12,"sell":15,"profit":3,quantity:27,"loss":0,"gender":"M"} {"stock":"SEE","buy"
{"stock":"SEE","buy":12,"sell":15,"profit":3,quantity:27,"loss":0,"gender":"M"}
{"stock":"SEE","buy":12,"sell":15,"profit":3,quantity:27,"loss":0,"gender":"M"}
{"stock":"SEE","buy":12,"sell":15,"profit":3,quantity:27,"loss":0,"gender":"M"}
下面是我的scala代码
val readStreamDFInd = sparkSession.readStream.format("kafka").option("kafka.bootstrap.servers", "localhost:9092")
.option("subscribe", "IndiaStocks")
.option("startingOffsets", "earliest")
.load()
//readStreamDFInd.printSchema()
val readStreamDFUS = sparkSession.readStream.format("kafka").option("kafka.bootstrap.servers", "localhost:9092")
.option("subscribe", "USStocks")
.option("startingOffsets", "earliest")
.load()
val schema = new StructType()
.add("stock", StringType)
.add("buy", IntegerType)
.add("sell", IntegerType)
.add("profit", IntegerType)
.add("quantity", IntegerType)
.add("loss", IntegerType)
.add("gender", StringType)
val stocksIndia = readStreamDFInd.selectExpr("CAST(value as STRING) as json").select(from_json($"json", schema).as("data")).select("data.*")
val stocksUSA = readStreamDFUS.selectExpr("CAST(value as STRING) as json").select(from_json($"json", schema).as("data")).select("data.*")
stocksIndia.printSchema() stocksUSA.writeStream
.format("console")
.outputMode("append").trigger(Trigger.ProcessingTime("5 seconds"))
.start()
.awaitTermination()
代码运行良好,您也可以在中看到 查看来自_json函数的
文档,会创建null
值,因为字符串是不可解析的
=>您缺少json字符串中数量
字段周围的引号。问题在于您的卡夫卡数据中,数量列应该在引号中。请在下面查看
{“股票”:“见”,“买”:12,“卖”:15,“利润”:3,“数量”:27,“损失”:0,“性别”:“M”}
{“股票”:“见”,“买”:12,“卖”:15,“利润”:3,“数量”:27,“损失”:0,“性别”:“M”}
{“股票”:“见”,“买”:12,“卖”:15,“利润”:3,“数量”:27,“损失”:0,“性别”:“M”}