一、最值

计算文本里面的最值（最大值、最小值、平均值），输出结果。

 

二、maven设置

<?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>com.mk</groupId><artifactId>spark-test</artifactId><version>1.0</version><name>spark-test</name><url>http://spark.mk.com</url><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target><scala.version>2.11.1</scala.version><spark.version>2.4.4</spark.version><hadoop.version>2.6.0</hadoop.version></properties><dependencies><!-- scala依赖--><dependency><groupId>org.scala-lang</groupId><artifactId>scala-library</artifactId><version>${scala.version}</version></dependency><!-- spark依赖--><dependency><groupId>org.apache.spark</groupId><artifactId>spark-core_2.11</artifactId><version>${spark.version}</version></dependency><dependency><groupId>org.apache.spark</groupId><artifactId>spark-sql_2.11</artifactId><version>${spark.version}</version></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.11</version><scope>test</scope></dependency></dependencies><build><pluginManagement><plugins><plugin><artifactId>maven-clean-plugin</artifactId><version>3.1.0</version></plugin><plugin><artifactId>maven-resources-plugin</artifactId><version>3.0.2</version></plugin><plugin><artifactId>maven-compiler-plugin</artifactId><version>3.8.0</version></plugin><plugin><artifactId>maven-surefire-plugin</artifactId><version>2.22.1</version></plugin><plugin><artifactId>maven-jar-plugin</artifactId><version>3.0.2</version></plugin></plugins></pluginManagement></build>
</project>

 

三、编程代码 

public class MaxApp implements SparkConfInfo{public static class IntegerComp implements Comparator<Integer>, Serializable{@Overridepublic int compare(Integer o1, Integer o2) {return o1.compareTo(o2);}}public static void main(String[]args){String filePath = "E:\\spark\\number.txt";SparkSession sparkSession = new MaxApp().getSparkConf("MaxApp");JavaRDD<Integer> numbers = sparkSession.sparkContext().textFile(filePath, 4).toJavaRDD().flatMap(v -> Arrays.asList(v.split("\n")).iterator()).map(Integer::new).cache();Integer max = numbers.max(new IntegerComp());Integer min = numbers.min(new IntegerComp());Integer sum = numbers.reduce(Integer::sum);long count = numbers.count();System.out.println("max:" + max);System.out.println("min:" + min);System.out.println("sum:" + sum);System.out.println("count:" + count);System.out.println("avg:" + sum * 1.0 / count);sparkSession.stop();}
}public interface SparkConfInfo {default SparkSession getSparkConf(String appName){SparkConf sparkConf = new SparkConf();if(System.getProperty("os.name").toLowerCase().contains("win")) {sparkConf.setMaster("local[4]");System.out.println("使用本地模拟是spark");}else{sparkConf.setMaster("spark://hadoop01:7077,hadoop02:7077,hadoop03:7077");sparkConf.set("spark.driver.host","192.168.150.1");//本地ip，必须与spark集群能够相互访问，如：同一个局域网sparkConf.setJars(new String[] {".\\out\\artifacts\\spark_test\\spark-test.jar"});//项目构建生成的路径}SparkSession session = SparkSession.builder().appName(appName).config(sparkConf).config(sparkConf).getOrCreate();return session;}
}

number.txt文件内容

100
24
43
774
43
37
78
42
68
89
49
543
36
888
258
538
79
6
67
99

输出

max:888
min:6
sum:3861
count:20
avg:193.05

 

遇到的问题

使用函数接口报错

 Integer max = numbers.max(Integer::compareTo);

org.apache.spark.SparkException: Task not serializableCaused by: java.io.NotSerializableException: com.mk.MaxApp$$Lambda$11/501991708
Serialization stack:- object not serializable (class: com.mk.MaxApp$$Lambda$11/501991708, value: com.mk.MaxApp$$Lambda$11/501991708@7fd26ad8)- field (class: scala.math.LowPriorityOrderingImplicits$$anon$7, name: cmp$2, type: interface java.util.Comparator)- object (class scala.math.LowPriorityOrderingImplicits$$anon$7, scala.math.LowPriorityOrderingImplicits$$anon$7@63b3ee82)- field (class: org.apache.spark.rdd.RDD$$anonfun$max$1, name: ord$10, type: interface scala.math.Ordering)- object (class org.apache.spark.rdd.RDD$$anonfun$max$1, <function0>)- field (class: org.apache.spark.rdd.RDD$$anonfun$max$1$$anonfun$apply$50, name: $outer, type: class org.apache.spark.rdd.RDD$$anonfun$max$1)- object (class org.apache.spark.rdd.RDD$$anonfun$max$1$$anonfun$apply$50, <function2>)

原因是函数接口对象实现没有序列化接口，需要实现序列化接口Serializable

Integer max = numbers.max(new IntegerComp());public static class IntegerComp implements Comparator<Integer>, Serializable{@Overridepublic int compare(Integer o1, Integer o2) {return o1.compareTo(o2);}}