本文為《Spark大型電商專案實戰》 系列文章之一，主要介紹使用Scala實現二次排序。

程式碼實現

在Scala IDE中的包com.erik.sparkproject中建立SortKey.scala，實現二次排序，程式碼如下：

package com.erik.sparkproject

/**
 * @author Erik
 */
class SortKey(val clickCount: Int, 
    val orderCount: Int, 
    val payCount: Int)
    extends Ordered[SortKey] with Serializable {

  def
 
 compare(that: SortKey): Int = {
    if(clickCount - that.clickCount != 0) {
      clickCount - that.clickCount
    } else if(orderCount - that.orderCount != 0) {
      orderCount - that.orderCount 
    } else if(payCount - that.payCount != 0) {
      payCount - that.payCount
    } else {
      0
    }
  }
}
 

測試

對實現的二次排序方法進行測試，新建SortKeyTest.scala，程式碼如下：

package com.erik.sparkproject

import org.apache.spark.SparkConf
import org.apache.spark.SparkContext


/**
 * @author Erik
 */
object SortKeyTest {

  def main(args: Array[String]): Unit = {
    val conf = new SparkConf()
        .setAppName("SortKeyTest"
 
)  
        .setMaster("local")  
    val sc = new SparkContext(conf) 

    val arr = Array(Tuple2(new SortKey(30, 35, 40), "1"),
        Tuple2(new SortKey(35, 30, 40), "2"),
        Tuple2(new SortKey(30, 38, 30), "3"))  
    val rdd = sc.parallelize(arr, 1)  

    val sortedRdd = rdd.sortByKey(false)

    for(tuple <- sortedRdd.collect()) {
      println(tuple._2)  
    }
  }

}

如果執行後結果為2 3 1，則說明測試通過。