这篇文章主要介绍“如何使用spark Context转成RDD”，在日常操作中，相信很多人在如何使用spark Context转成RDD问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”如何使用spark Context转成RDD”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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一. 背景
在spark rdd转换算子中join和cogroup是有些需要区分的算子转换，这里使用示例来说明一下。
二. 示例
1.构建List示例数据
List> studentsList = Arrays.asList(
new Tuple2(1,"xufengnian"),
new Tuple2(2,"xuyao"),
new Tuple2(2,"wangchudong"),
new Tuple2(3,"laohuang")
);
List> scoresList = Arrays.asList(
new Tuple2(1,100),
new Tuple2(2,90),
new Tuple2(3,80),
new Tuple2(1,101),
new Tuple2(2,91),
new Tuple2(3,81),
new Tuple2(3,71)
);
2.使用sparkContext转成RDD
JavaPairRDD studentsRDD = sc.parallelizePairs(studentsList);
JavaPairRDD scoresRDD = sc.parallelizePairs(scoresList);
//studentsRDD 为：List>
//(1,xufengnian)(2,xuyao)(2,wangchudong)(3,laohuang),下面进行打印查看
studentsRDD.foreach(new VoidFunction>(){
public void call(Tuple2 tuple){
System.out.println(tuple._1);//1 2 3
System.out.println(tuple._2);// xufengnian xuyao laohuang
}
});
3.进行join
/*
前面数据
(1,xufengnian)(2,xuyao)(2,"wangchudong")(3,laohuang)
(1,100)(2,90)(3,80)(1,101)(2,91)(3,81)(3,71)
join之后：
(1,(xufengnian,100))(1,(xufengnian,101))(3,(laohuang,80))(3,(laohuang,81))(3,(laohuang,71))
(2,(xuyao,90))(2,(xuyao,91))(2,(wangchudong,90))(2,(wangchudong,91))
*/
JavaPairRDD> studentScores = studentsRDD.join(scoresRDD);
//join为key相同的join,key不变，value变成(string,integer)
studentScores.foreach(new VoidFunction>>() {
private static final long serialVersionUID = 1L;
@Override
public void call(Tuple2> student)
throws Exception {
System.out.println("student id: " + student._1);//1 1 3
System.out.println("student name: " + student._2._1);//xufengnian xufengnian laohuang
System.out.println("student score: " + student._2._2);//100 101 80
System.out.println("===================================");
}
});
4.进行cogroup
/*
前面的数据
(1,xufengnian)(2,xuyao)(2,"wangchudong")(3,laohuang)
(1,100)(2,90)(3,80)(1,101)(2,91)(3,81)(3,71)
cogroup之后：
(1,([xufengnian],[100,101])) (3,([laohuang],[80,81,71])) (2,([xuyao,wangchudong],[90,91]))
*/
JavaPairRDD,Iterable>> studentScores2 = studentsRDD.cogroup(scoresRDD);
studentScores2.foreach(new VoidFunction, Iterable>>>() {
@Override
public void call(Tuple2, Iterable>> stu) throws Exception {
System.out.println("stu id:"+stu._1);//1 3
System.out.println("stu name:"+stu._2._1);//[xufengnian] [laohuang]
System.out.println("stu score:"+stu._2._2);//[100,101] [80,81,71]
Iterable integers = stu._2._2;
for (Iterator iter = integers.iterator(); iter.hasNext();) {
Integer str = (Integer)iter.next();
System.out.println(str);//100 101 80 81 71
}
System.out.println("===================================");
}
});
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