在window10下安装了hadoop，用ida创建maven项目。
<properties>
<spark.version>2.2.0</spark.version>
<scala.version>2.11</scala.version>
<java.version>1.8</java.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-sql_${scala.version}</artifactId>
<version>${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-yarn_${scala.version}</artifactId>
<version>${spark.version}</version>
</dependency> <dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.16</version>
</dependency>
</dependencies> <build>
<finalName>learnspark</finalName>
<plugins>
<plugin>
<groupId>net.alchim31.maven</groupId>
<artifactId>scala-maven-plugin</artifactId>
<version>3.2.2</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>testCompile</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.0.0</version>
<configuration>
<archive>
<manifest>
<mainClass>learn</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
数据准备：
{"name":"张3", "age":20}
{"name":"李4", "age":20}
{"name":"王5", "age":20}
{"name":"赵6", "age":20}
路径：data/input/user/user.json
程序：
package com.zouxxyy.spark.sql import org.apache.spark.SparkConf
import org.apache.spark.sql.expressions.{Aggregator, MutableAggregationBuffer, UserDefinedAggregateFunction}
import org.apache.spark.sql.types.{DataType, DoubleType, LongType, StructType}
import org.apache.spark.sql.{Column, DataFrame, Dataset, Encoder, Encoders, Row, SparkSession, TypedColumn} /**
* UDF：用户自定义函数
*/ object UDF { def main(args: Array[String]): Unit = {
System.setProperty("hadoop.home.dir","D:\\gitworkplace\\winutils\\hadoop-2.7.1" )
//这个是用来指定我的hadoop路径的，如果你的hadoop环境变量没问题，可以不写
val sparkConf: SparkConf = new SparkConf().setMaster("local[*]").setAppName("UDF") // 创建SparkSession
val spark: SparkSession = SparkSession.builder.config(sparkConf).getOrCreate() import spark.implicits._ // 从json中read得到的是DataFrame
val frame: DataFrame = spark.read.json("data/input/user/user.json") frame.createOrReplaceTempView("user") // 案例一：自定义一个简单的函数测试
spark.udf.register("addName", (x:String)=> "Name:"+x) spark.sql("select addName(name) from user").show() // 案例二：自定义一个弱类型聚合函数测试 val udaf1 = new MyAgeAvgFunction spark.udf.register("avgAge", udaf1) spark.sql("select avgAge(age) from user").show() // 案例三：自定义一个强类型聚合函数测试 val udaf2 = new MyAgeAvgClassFunction // 将聚合函数转换为查询列
val avgCol: TypedColumn[UserBean, Double] = udaf2.toColumn.name("aveAge") // 用强类型的Dataset的DSL风格的编程语法
val userDS: Dataset[UserBean] = frame.as[UserBean] userDS.select(avgCol).show() spark.stop()
}
} /**
* 自定义内聚函数(弱类型)
*/ class MyAgeAvgFunction extends UserDefinedAggregateFunction{ // 输入的数据结构
override def inputSchema: StructType = {
new StructType().add("age", LongType)
} // 计算时的数据结构
override def bufferSchema: StructType = {
new StructType().add("sum", LongType).add("count", LongType)
} // 函数返回的数据类型
override def dataType: DataType = DoubleType // 函数是否稳定
override def deterministic: Boolean = true // 计算前缓存区的初始化
override def initialize(buffer: MutableAggregationBuffer): Unit = {
// 没有名称，只有结构
buffer(0) = 0L
buffer(1) = 0L
} // 根据查询结果，更新缓存区的数据
override def update(buffer: MutableAggregationBuffer, input: Row): Unit = {
buffer(0) = buffer.getLong(0) + input.getLong(0)
buffer(1) = buffer.getLong(1) + 1
} // 多个节点的缓存区的合并
override def merge(buffer1: MutableAggregationBuffer, buffer2: Row): Unit = {
buffer1(0) = buffer1.getLong(0) + buffer2.getLong(0)
buffer1(1) = buffer1.getLong(1) + buffer2.getLong(1)
} // 计算缓存区里的东西，得最终返回结果
override def evaluate(buffer: Row): Any = {
buffer.getLong(0).toDouble / buffer.getLong(1)
}
} /**
* 自定义内聚函数(强类型)
*/ case class UserBean (name : String, age : BigInt) // 文件读取数字默认是BigInt
case class AvgBuffer(var sum: BigInt, var count: Int) class MyAgeAvgClassFunction extends Aggregator[UserBean, AvgBuffer, Double] { // 初始化缓存区
override def zero: AvgBuffer = {
AvgBuffer(0, 0)
} // 输入数据和缓存区计算
override def reduce(b: AvgBuffer, a: UserBean): AvgBuffer = {
b.sum = b.sum + a.age
b.count = b.count + 1
// 返回b
b
} // 缓存区的合并
override def merge(b1: AvgBuffer, b2: AvgBuffer): AvgBuffer = {
b1.sum = b1.sum + b2.sum
b1.count = b1.count + b2.count b1
} // 计算返回值
override def finish(reduction: AvgBuffer): Double = {
reduction.sum.toDouble / reduction.count
} override def bufferEncoder: Encoder[AvgBuffer] = Encoders.product override def outputEncoder: Encoder[Double] = Encoders.scalaDouble
}