scala-xml : how to move child to another parent node

[RobsonNLPT]

Hi all

The mandatory rowTag for writing to XML cause doesn't make any sense as I have the complete nested dataframe schema.

In my case I need to implement an extra step to remove that extra node (default: Row) after xml generation.

I need some examples using scala-xml library and Transform/RuleTransformer/RewriteRule to move child to root parent and remove the node "Row" 

Any help?

[Kaniz]

Hi @RobsonNLPT, Working with XML in Scala using the scala-xml library can be powerful and flexible.

Let’s break down your requirements and provide an example of how to achieve this.

1. Removing the “Row” Node: When converting a DataFrame to XML, the default behaviour is to wrap each row in a <Row> node. However, you want to remove this extra layer and directly nest the child elements under the root parent. We can achieve this using the scala-xml library.

2. Example Using RuleTransformer: We’ll use the RuleTransformer to transform the XML structure. Specifically, we’ll create a custom rule that removes the <Row> node and moves its children to the root parent.

Here’s an example of how you can achieve this:

import scala.xml._
import scala.xml.transform._

// Sample XML with the <Row> node
val xmlWithRow: Elem =
  <root>
    <Row>
      <name>Alice</name>
      <age>30</age>
    </Row>
    <Row>
      <name>Bob</name>
      <age>25</age>
    </Row>
  </root>

// Custom rule to remove <Row> and move children to root
class RemoveRowRule extends RewriteRule {
  override def transform(node: Node😞 Seq[Node] = node match {
    case Elem(_, "Row", _, _, children @ _*) => children
    case other => other
  }

  // Apply the rule to the entire XML
  def apply(xml: Node😞 Node = new RuleTransformer(this).transform(xml)
}

// Apply the rule to the sample XML
val transformedXml: Node = new RemoveRowRule().apply(xmlWithRow)

// Print the transformed XML
println(transformedXml)

In this example:

• We define a custom RemoveRowRule that matches <Row> nodes and replaces them with their children.
• The RuleTransformer applies this rule to the entire XML structure.
• The resulting transformedXml will have the <Row> nodes removed, and their children will be directly under the root <root> node.

Feel free to adapt this example to your specific use case by replacing the sample XML with your actual data. Remember to adjust the rule to match your schema and nesting structure.

Remember that XML in Scala is immutable, so the transformation creates a new XML structure without modifying the original.

I hope this helps! Let me know if you have any further questions or need additional examples. 🌟

[RobsonNLPT]

Hi Kaniz. Thank you

Your code is not correct

command-3498107737134944:21: error: type mismatch; found : Seq[scala.xml.Node] required: scala.xml.Node def apply(xml: Node): Node = new RuleTransformer(this).transform(xml)

Can you check?

[RobsonNLPT · Accepted solution]

I just adapted the code and it worked. Thank you.