实验 4 RDD 编程初级实践

注意：spark的编码格式是utf-8，其他的格式会有乱码，所以文件要使用utf-8编码

pom.xml：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>gao</groupId>
    <artifactId>WordCount</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <spark.version>2.1.0</spark.version>
        <scala.version>2.11</scala.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_${scala.version}</artifactId>
            <version>${spark.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-streaming_${scala.version}</artifactId>
            <version>${spark.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-sql_${scala.version}</artifactId>
            <version>${spark.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-hive_${scala.version}</artifactId>
            <version>${spark.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-mllib_${scala.version}</artifactId>
            <version>${spark.version}</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>

            <plugin>
                <groupId>org.scala-tools</groupId>
                <artifactId>maven-scala-plugin</artifactId>
                <version>2.15.2</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.6.0</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.19</version>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>

        </plugins>
    </build>

</project>

（1）该系总共有多少学生； 

（2）该系共开设来多少门课程；

（3）Tom 同学的总成绩平均分是多少；

（4）求每名同学的选修的课程门数；

（5）该系 DataBase 课程共有多少人选修；

（6）各门课程的平均分是多少；

（7）使用累加器计算共有多少人选了 DataBase 这门课。

import org.apache.spark.SparkConf
import org.apache.spark.SparkContext
object one {
  def main(args: Array[String]) {
    val conf = new SparkConf()
    conf.setMaster("local")
      .setAppName("text1")
    val sc = new SparkContext(conf)
    val rdd = sc.textFile("C:\\Users\\Administrator\\Desktop\\Data01.txt")
    //该系总共有多少学生；
    val par=rdd.map( row=>row.split(",")(0))
    var count=par.distinct()
    println("学生总人数："+count.count())
    //该系共开设来多少门课程；
    val couse=rdd.map( row=>row.split(",")(1))
    println("课程数："+couse.distinct().count())
   //Tom 同学的总成绩平均分是多少；
    val pare = rdd.filter(row=>row.split(",")(0)=="Tom")
    /*pare.foreach(println)*/
    pare.map(row=>(row.split(",")(0),row.split(",")(2).toInt))
      .mapValues(x=>(x,1))
      .reduceByKey((x,y) => (x._1+y._1,x._2 + y._2))
      .mapValues(x => (x._1 / x._2))
      .collect().foreach(x=>println("Tom的平均成绩："+x._2))
    //求每名同学的选修的课程门数；
    val pare2 = rdd.map(row=>(row.split(",")(0),row.split(",")(1)))
    pare2.mapValues(x => (x,1)).reduceByKey((x,y) => (" ",x._2 + y._2)).mapValues(x => x._2).foreach(println)
   //该系 DataBase 课程共有多少人选修；
    val pare3 = rdd.filter(row=>row.split(",")(1)=="DataBase")
    println("DataBase的选修人数："+pare3.count)
    // 各门课程的平均分是多少；
    val pare4 = rdd.map(row=>(row.split(",")(1),row.split(",")(2).toInt))
    pare4.mapValues(x=>(x,1))
      .reduceByKey((x,y) => (x._1+y._1,x._2 + y._2))
      .mapValues(x => (x._1/ x._2))
      .collect().foreach(println)
    //使用累加器计算共有多少人选了 DataBase 这门课。
    val pare5 = rdd.filter(row=>row.split(",")(1)=="DataBase")
      .map(row=>(row.split(",")(1),1))
    val accum = sc.longAccumulator("My Accumulator")
    pare5.values.foreach(x => accum.add(x))
    println("选了 DataBase 这门课的人数："+accum.value)
  }
}

2.对于两个输入文件 A 和 B，编写 Spark 独立应用程序，对两个文件进行合并，并剔除其 中重复的内容，得到一个新文件 C

import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf
import org.apache.spark.HashPartitioner

object two
{
  def main(args: Array[String]) {
    val conf = new SparkConf()
    conf.setMaster("local")
      .setAppName("text2")
    val sc = new SparkContext(conf)
    val dataFile = "C:\\Users\\Administrator\\Desktop\\data"
    val data = sc.textFile(dataFile,2)
    val res = data.filter(_.trim().length>0).map(line=>(line.trim,"\t"))
      .partitionBy(new HashPartitioner(1)).groupByKey().sortByKey().keys
    res.saveAsTextFile("result")
  }
}

3.每个输入文件表示班级学生某个学科的成绩，每行内容由两个字段组成，第一个是学生 名字，第二个是学生的成绩；编写 Spark 独立应用程序求出所有学生的平均成绩，并输出到 一个新文件中。

import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf
import org.apache.spark.HashPartitioner

object three {
  def main(args: Array[String]) {
    val conf = new SparkConf()
    conf.setMaster("local")
      .setAppName("text3")
    val sc = new SparkContext(conf)
    val dataFile = "C:\\Users\\Administrator\\Desktop\\data1"
    val data = sc.textFile(dataFile,3)
    val res = data.filter(_.trim().length>0)
      .map(line=>(line.split("\t")(0).trim()
        ,line.split("\t")(1).trim().toInt))
      .partitionBy(new HashPartitioner(1))
      .groupByKey().map(x => {
      var n = 0
      var sum = 0.0
      for(i <- x._2){
        sum = sum + i
        n = n +1
      }
      val avg = sum/n
      val format = f"$avg%1.2f".toDouble
      (x._1,format)
    })
    res.saveAsTextFile("result1")
  }
}

原文地址：https://www.cnblogs.com/miria-486/p/10519630.html