Spark之 RDD转换成DataFrame的Scala实现

水深无声 2022-01-07 10:57 284阅读 0赞

### 依赖 ###

<dependency>
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-sql_2.11</artifactId>
        <version>2.1.3</version>
    </dependency>

### RDD转化成DataFrame:通过StructType指定schema ###

package com.zy.sparksql

import org.apache.spark.SparkContext  
import org.apache.spark.rdd.RDD  
import org.apache.spark.sql.types.\{IntegerType, StringType, StructType\}  
import org.apache.spark.sql.\{DataFrame, Row, SparkSession\}

/\*\*  
  \* RDD转化成DataFrame:通过StructType指定schema  
  \*/  
object StructTypeSchema \{  
  def main(args: Array\[String\]): Unit = \{  
    //创建sparkSession对象  
    val sparkSession: SparkSession = SparkSession.builder().appName("StructTypeSchema").master("local\[2\]").getOrCreate()  
    //获取sparkContext  
    val sc: SparkContext = sparkSession.sparkContext  
    //设置日志级别  
    sc.setLogLevel("WARN")

//读取文件  
    val textFile: RDD\[String\] = sc.textFile("D:\\\\person.txt")  
    //切分文件  
    val lineArrayRDD: RDD\[Array\[String\]\] = textFile.map(\_.split(","))

//关联对象  
    val rowRDD: RDD\[Row\] = lineArrayRDD.map(x => Row(x(0).toInt, x(1), x(2).toInt))  
    //创建rdd的schema信息  
    val schema: StructType = (new StructType)  
      .add("id", IntegerType, true, "id")  
      .add("name", StringType, false, "姓名")  
      .add("age", IntegerType, true, "年龄")  
    //根据rdd和schema信息创建DataFrame  
    val personDF: DataFrame = sparkSession.createDataFrame(rowRDD, schema)

//DSL操作  
    personDF.show()

//sql 操作  
    //将df注册成表  
    personDF.createTempView("person")

sparkSession.sql("select \* from person where id =3").show()

sparkSession.stop()  
  \}  
\}

package com.zy.sparksql

import org.apache.spark.SparkContext  
import org.apache.spark.rdd.RDD  
import org.apache.spark.sql.\{DataFrame, SparkSession\}

RDD转化成DataFrame:利用反射机制推断schema  
/\*\*  
  \* RDD转化成DataFrame:利用反射机制推断schema  
  \*/

//todo 定义一个样例类  
case class Person(id: Int, name: String, age: Int)

object CaseClassSchema \{  
  def main(args: Array\[String\]): Unit = \{  
    //构建sparkSession 指定appName和master地址(本地测试local)  
    val sparkSession: SparkSession = SparkSession.builder().appName("CaseClassSchema").master("local\[2\]").getOrCreate()  
    //获取sparkContext  
    val sc: SparkContext = sparkSession.sparkContext

//设置日志输出级别  
    sc.setLogLevel("WARN")

//加载数据  
    val dataRDD: RDD\[String\] = sc.textFile("D:\\\\person.txt")  
    //切分数据  
    val lineArrayRDD: RDD\[Array\[String\]\] = dataRDD.map(\_.split(","))  
    //将rdd和person样例类关联  
    val personRDD: RDD\[Person\] = lineArrayRDD.map(x => Person(x(0).toInt, x(1), x(2).toInt))

//将rdd转换成dataFrame 导入隐式转换  
    import sparkSession.implicits.\_  
    val personDF: DataFrame = personRDD.toDF

//DSL语法  
    personDF.show()  
    personDF.printSchema()  
    personDF.select("name").show()  
    personDF.filter($"age" > 30).show()

println("---------------------------------------------")

//sql语法  
    //首先要创建临时视图  
    personDF.createTempView("person")  
    sparkSession.sql("select \* from person where id>1").show()

sparkSession.stop()  
  \}  
\}