How to get the TypeTag for a class in Java

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I'm trying to call the functions.typedLit from Spark library in my other question. And it asks for two parameters, a literal object and its type (a TypeTag).

The first argument, I can come up with myself (I think). But as for the second one, I don't know how to instantiate an object for it. I'm trying to pass the TypeTag<Seq<Integer>> as the second parameter.

Can someone please tell how to create the TypeTag for Seq<Integer> in Java? Here's the code I'm trying to complete:

Seq<Integer> seq =  JavaConverters
                      .asScalaIteratorConverter((new ArrayList<Integer>()).iterator())
                      .asScala()
                      .toSeq();
Column litColumn = functions.<Seq<Integer>>typedLit(seq, ???)
apache-spark scala java
1 Answers

In your other question I said

and supplying the CanBuildFrom argument from Java is... technically possible, but not something you want to do.

Unfortunately, for TypeTag it's even less possible: unlike CanBuildFrom, they aren't supplied by a library, but built into Scala compiler.

The best advice I can give is to create a Scala file supplying the type tags you need to use from Java, since you only should need a limited number of them:

object TypeTags {
  val SeqInteger = typeTag[Seq[Integer]]
  ...
  // or 
  val Integer = typeTag[Integer]
  def Seq[A](implicit tt: TypeTag[A]) = typeTag[Seq[A]]
}

and then from Java TypeTags.SeqInteger or TypeTags.Seq(TypeTags.Integer).

In other places Spark provides special API for use from Java (look for .java packages), but I couldn't find one for functions.typedLit.

alexey_r_92040
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