spark 下java list 或者scala list 转DataFrame or DataSet 总结

一、JAVA list 转 DataFrame or DataSet

case class CaseJava(
                           var num: String,
                           var id: String,
                           var start_time: String,
                           var istop_time: String)
						   
val listData: java.util.List[CaseJava] = new java.util.ArrayList[CaseJava]

listData.add(new CaseJava("11","22","33","44"))
val dataFrame = spark.createDataFrame(listData, classOf[CaseJava])

二、scala MutableList 转 DataFrame or DataSe

1、方式一：

val spark = SparkSession.builder().appName("Spark-SQL").master("local[2]").getOrCreate()

import spark.implicits._

var tom = new TestPerson("Tom Hanks",37,35.5)
var sam = new TestPerson("Sam Smith",40,40.5)

val PersonList = mutable.MutableList[TestPerson]()

//Adding data in list
PersonList += tom
PersonList += sam

//It will be work.
var personDS = Seq(PersonList).toDS()

2、方式二：

case class TestPerson(name: String, age: Long, salary: Double)

val spark = SparkSession.builder().appName("List to Dataset").master("local[*]").getOrCreate()

var tom = new TestPerson("Tom Hanks",37,35.5)
var sam = new TestPerson("Sam Smith",40,40.5)
   
// mutable.MutableList[TestPerson]() is not required , i used below way which was 
// cleaner
val PersonList =  List(tom,sam)

import spark.implicits._
PersonList.toDS().show

3、方式三：

case class TestPerson(name: String, age: Long, salary: Double)
val tom = TestPerson("Tom Hanks",37,35.5)
val sam = TestPerson("Sam Smith",40,40.5)
val PersonList = mutable.MutableList[TestPerson]()
PersonList += tom
PersonList += sam

val personDS = PersonList.toDS()
println(personDS.getClass)
personDS.show()

val personDF = PersonList.toDF()
println(personDF.getClass)
personDF.show()
personDF.select("name", "age").show()

 更多请参考：https://stackoverflow.com/questions/39397652/convert-scala-list-to-dataframe-or-dataset