我希望镶木地板文件数据采用以下字符串格式.有人能帮我吗

Question

我正在尝试获取以下格式的数据。有人能帮我为spark和scala创建一个UDF吗。我是新手。有人能帮忙吗？我期望的输出是字符串输出

Java|XX||Scala|XA

如果它在数组中有一个continuation值，它应该继续请帮帮我，非常重要的任务

root
|-- name: string (nullable = true)
|-- booksIntersted: array (nullable = true)
|    |-- element: struct (containsNull = true)
|    |    |-- name: string (nullable = true)
|    |    |-- author: string (nullable = true)
|    |    

+----------+-----------------------------------+
|name      |booksIntersted                     |
+----------+-----------------------------------+
|James     |[[Java, XX], [Scala, XA]]|
|Michael   |[[Java, XY], [Scala, XB]]|
|Robert    |[[Java, XZ], [Scala, XC]]|
|Washington|null                               |
+----------+-----------------------------------+
```

Answer 1

检查以下代码。

val finalDF = df
.withColumn(
"booksIntersted",
when(
size($"booksIntersted") > 0,
expr("concat_ws('||',transform(booksIntersted,x -> concat(x.name,'|',x.author)))")
)
)

finalDF.printSchema

root
|-- name: string (nullable = true)
|-- booksIntersted: string (nullable = true)

finalDF.show(false(

+----------+-----------------+
|name      |booksIntersted   |
+----------+-----------------+
|James     |Java|XX||Scala|XA|
|Michael   |Java|XY||Scala|XB|
|Robert    |Java|XZ||Scala|XC|
|Washington|null             |
+----------+-----------------+

以csv格式写入数据

finalDF
.repartition(1)
.write
.format("csv")
.option("header","true")
.save("/tmp/csv/data")

cd /tmp/csv/data
> cat part-00000-c8527721-5b25-4689-bfe4-028ac2873def-c000.csv
name,booksIntersted
James,Java|XX||Scala|XA
Michael,Java|XY||Scala|XB
Robert,Java|XZ||Scala|XC
Washington,""

使用udf

scala> val combine = udf((row: Seq[Row]) => {
row
.map(r => r.getAs[String]("name") + "|" + r.getAs[String]("author"))
.reduce(_+ "||" + _)
})

scala> df
.withColumn(
"booksInterstedNew",
when(
size($"booksIntersted") > 0,
combine($"booksIntersted")
)
)
.show(false)

+----------+-------------------------+-----------------+
|name      |booksIntersted           |booksInterstedNew|
+----------+-------------------------+-----------------+
|James     |[[Java, XX], [Scala, XA]]|Java|XX||Scala|XA|
|Michael   |[[Java, XY], [Scala, XB]]|Java|XY||Scala|XB|
|Robert    |[[Java, XZ], [Scala, XC]]|Java|XZ||Scala|XC|
|Washington|[]                       |null             |
+----------+-------------------------+-----------------+