如何从Scala中调用Groovy脚本？附XML内嵌Groovy示例解析

Let's walk through how to extract and execute the Groovy script embedded in your XML file from Scala. We'll break this into two main parts: parsing the XML to get the script content, then running that script using Groovy's libraries.

Step 1: Extract the Groovy Script from XML #

First, we need to pull the Groovy code out of the <script> tag's CDATA section. You mentioned a Java utility NREUtils.readXml that returns a List<Fact>—since Scala plays nice with Java, we can reuse that directly.

Assuming your Fact class has a method to retrieve the script (like getScript()), here's how to grab the relevant code:

import com.yourpackage.NREUtils
import com.yourpackage.Fact
import scala.jdk.CollectionConverters._

// Read XML into a list of Fact objects using your existing Java utility
val factList: List[Fact] = NREUtils.readXml("path/to/your/facts.xml").asScala.toList

// Find the "ItemPrice" fact and extract its script
val itemPriceScript = factList
  .find(_.getId == "ItemPrice")
  .map(_.getScript)
  .getOrElse(throw new IllegalArgumentException("ItemPrice fact not found"))

If you prefer a pure Scala XML parsing approach (no Java utility required), use Scala's built-in XML handling:

import scala.xml.XML

// Load the XML file
val xml = XML.loadFile("path/to/your/facts.xml")

// Extract the script text from the CDATA section
val groovyScript = (xml \ "fact" \ "script").text.trim

Step 2: Execute the Groovy Script in Scala #

To run the Groovy script, you'll need to add the Groovy library to your project. Update your build.sbt with this dependency:

libraryDependencies += "org.codehaus.groovy" % "groovy" % "3.0.17" // Use the latest stable version

Then use GroovyShell—the simplest way to execute Groovy code from Scala:

import groovy.lang.GroovyShell

// Create a GroovyShell instance
val shell = new GroovyShell()

// Execute the script and cast the result to the expected type
val calculatedPrice = shell.evaluate(groovyScript).asInstanceOf[Double]

println(s"Calculated Item Price: $calculatedPrice") // Outputs 50.0 for your example

If you need to pass custom variables to the script (instead of hardcoding them inside the CDATA), use a Binding:

import groovy.lang.GroovyShell
import groovy.lang.Binding

// Define variables to pass to the script
val binding = new Binding()
binding.setVariable("Value_Sales", 750.0)
binding.setVariable("Unit_Sales", 15.0)

// Execute the script with the custom binding
val shell = new GroovyShell(binding)
val customPrice = shell.evaluate(groovyScript).asInstanceOf[Double]

println(s"Custom Calculated Price: $customPrice") // Outputs 50.0 here too

Full Combined Example #

Here's a complete Scala program that ties everything together:

import scala.xml.XML
import groovy.lang.GroovyShell

object GroovyScriptRunner extends App {
  // Extract script from XML
  val xml = XML.loadFile("path/to/your/facts.xml")
  val groovyScript = (xml \ "fact" \ "script").text.trim

  // Execute the script
  val shell = new GroovyShell()
  val itemPrice = shell.evaluate(groovyScript).asInstanceOf[Double]

  println(s"Final Item Price Result: $itemPrice") // Prints 50.0
}

Key Notes #

• Always handle potential errors in production code (e.g., missing facts, script execution failures, type casting issues).
• Ensure your project's classpath includes the Groovy library—this is critical for the script execution to work.
• If you're using the Java NREUtils utility, make sure the Scala code has access to the Fact class and its methods.

内容的提问来源于stack exchange，提问作者Sujith AK