从火花中的卡夫卡爵士中寻找最低温度

Question

我从kafka获取json消息并将其转换为key，pair值。这是我的kafka制作人代码。

val r = scala.util.Random
      for( a <- 1 to 100){
   var id1=s"ST_${r.nextInt(50)}"
   val date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
   val d = new Date()
   val dateString = date.format(d)
   val date1=date.toString
   val temp=r.nextInt(90)
   val press=r.nextInt(70)
   val hum=r.nextInt(30)
   var first= new data(id1,dateString,temp,press,hum)


 implicit val writes = Json.writes[data]
   val jsonString = Json.toJson(first).toString

   val record = new ProducerRecord(TOPIC, "key", jsonString)

   producer.send(record)
   Thread.sleep(5000)

对于我正在使用的火花消费者

val lines = KafkaUtils.createStream(ssc, "localhost:2181", "spark-streaming-consumer-group", Map("test1" -> 5))
val k=lines.map(_._2)

我的输出是

{"id":"ST_44","date":"2018-02-23 23:56:12","temp":76,"pressure":40,"humidity":29})

我想找到所有100个站点的最低温度值和id。我该怎么办？