Spark查看变量数据类型和Dataframe每列类型

• 变量类型

val x = 5
println(x.getClass)

结果是：
class java.lang.Integer

• 查看Dataframe每列类型

val data = Array(("1", "2", "3", "4", "5"), ("6", "7", "8", "9", "10"))
val df = spark.createDataFrame(data).toDF("col1", "col2", "col3", "col4", "col5")

df.dtypes
结果：

 Array[(String, String)] = Array((col1,StringType), (col2,StringType), (col3,StringType), (col4,StringType), (col5,StringType))

• 用Map存储列名和类型

val a = df.dtypes.toMap
println(a)

a: scala.collection.immutable.Map[String,String] = Map(col3 -> StringType, col2 -> StringType, col5 -> StringType, col1 -> StringType, col4 -> StringType)
Map(col3 -> StringType, col2 -> StringType, col5 -> StringType, col1 -> StringType, col4 -> StringType)