10、自定义排序
文本中有如下内容：
1 5
2 4
3 6
1 3
2 1
现要求对文本行进行排序，第一列相同时，比较第二列
Java版：
package sparkcore.java;
import java.io.Serializable;
import scala.math.Ordered;
/**
* 自定义的二次排序key
*/
public class SecondarySortKey implements Ordered<SecondarySortKey>, Serializable {
private static final long serialVersionUID = -2366006422945129991L;
// 首先在自定义key里面，定义需要进行排序的列
private int first;
private int second;
public SecondarySortKey(int first, int second) {
this.first = first;
this.second = second;
}
@Override
// 大于
public boolean $greater(SecondarySortKey other) {
if (this.first > other.getFirst()) {
return true;
} else if (this.first == other.getFirst() && this.second > other.getSecond()) {
return true;
}
return false;
}
@Override
// 大于等于
public boolean $greater$eq(SecondarySortKey other) {
if (this.$greater(other)) {
return true;
} else if (this.first == other.getFirst() && this.second == other.getSecond()) {
return true;
}
return false;
}
@Override
// 小于
public boolean $less(SecondarySortKey other) {
if (this.first < other.getFirst()) {
return true;
} else if (this.first == other.getFirst() && this.second < other.getSecond()) {
return true;
}
return false;
}
@Override
// 小于等于
public boolean $less$eq(SecondarySortKey other) {
if (this.$less(other)) {
return true;
} else if (this.first == other.getFirst() && this.second == other.getSecond()) {
return true;
}
return false;
}
@Override
public int compare(SecondarySortKey other) {
if (this.first - other.getFirst() != 0) {
return this.first - other.getFirst();
} else {
return this.second - other.getSecond();
}
}
@Override
public int compareTo(SecondarySortKey other) {
return this.compare(other);
}
// 为要进行排序的多个列，提供getter和setter方法，以及hashcode和equals方法
public int getFirst() {
return first;
}
public void setFirst(int first) {
this.first = first;
}
public int getSecond() {
return second;
}
public void setSecond(int second) {
this.second = second;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + first;
result = prime * result + second;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
SecondarySortKey other = (SecondarySortKey) obj;
if (first != other.first)
return false;
if (second != other.second)
return false;
return true;
}
}package sparkcore.java;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.PairFunction;
import org.apache.spark.api.java.function.VoidFunction;
import scala.Tuple2;
/**
* 二次排序
* 1、实现自定义的key，要实现Ordered接口和Serializable接口，在key中实现自己对多个列的排序算法
* 2、将包含文本的RDD，映射成key为自定义key，value为文本的JavaPairRDD
* 3、使用sortByKey算子按照自定义的key进行排序
* 4、再次映射，剔除自定义的key，只保留文本行
*/
public class SecondarySort {
public static void main(String[] args) {
SparkConf conf = new SparkConf().setAppName("SecondarySort").setMaster("local");
JavaSparkContext sc = new JavaSparkContext(conf);
JavaRDD<String> lines = sc.textFile("test.txt");
JavaPairRDD<SecondarySortKey, String> pairs = lines.mapToPair(
new PairFunction<String, SecondarySortKey, String>() {
private static final long serialVersionUID = 1L;
@Override
public Tuple2<SecondarySortKey, String> call(String line) throws Exception {
String[] lineSplited = line.split(" ");
SecondarySortKey key = new SecondarySortKey(Integer.valueOf(lineSplited[0]),
Integer.valueOf(lineSplited[1]));
//自定义Key做为key，原文本行作为value值
return new Tuple2<SecondarySortKey, String>(key, line);
}
});
JavaPairRDD<SecondarySortKey, String> sortedPairs = pairs.sortByKey();
JavaRDD<String> sortedLines = sortedPairs.map(
new Function<Tuple2<SecondarySortKey, String>, String>() {
private static final long serialVersionUID = 1L;
@Override
public String call(Tuple2<SecondarySortKey, String> v1) throws Exception {
return v1._2;//key丢弃，取文本行
}
});
sortedLines.foreach(new VoidFunction<String>() {
private static final long serialVersionUID = 1L;
@Override
public void call(String t) throws Exception {
System.out.println(t);
}
});
sc.close();
}
}
Scala版本：
package sparkcore.scala
class SecondSortKey(val first: Int, val second: Int)
extends Ordered[SecondSortKey] with Serializable {
def compare(that: SecondSortKey): Int = {
if (this.first - that.first != 0) {
this.first - that.first
} else {
this.second - that.second
}
}
}package sparkcore.scala
import org.apache.spark.SparkConf
import org.apache.spark.SparkContext
object SecondSort {
def main(args: Array[String]): Unit = {
val conf = new SparkConf()
.setAppName("SecondSort")
.setMaster("local")
val sc = new SparkContext(conf)
val lines = sc.textFile("test.txt", 1)
val pairs = lines.map { line => (
new SecondSortKey(line.split(" ")(0).toInt, line.split(" ")(1).toInt),
line)}
val sortedPairs = pairs.sortByKey()
val sortedLines = sortedPairs.map(sortedPair => sortedPair._2)
sortedLines.foreach { sortedLine => println(sortedLine) }
}
}
原文出自 江正军 技术博客，博客链接：www.cnblogs.com/jiangzhengjun
