Use Javascript scripting engine in Java 17

Question

I have to move a project from Java 8 to Java 17.

I could solve most issues, but it contains a method, in which I use the ScriptEngineManager to evaluate a mathematical term.

 ScriptEngineManager mgr = new ScriptEngineManager();
 ScriptEngine e = mgr.getEngineByName("JavaScript");
 
 String t = "5*7";
 if (isMathTerm(t)) {
    System.out.println(e.eval(t).toString());
 }

In Java 8 it works as required, but in Java 17 e is always null.

According to google, the JavaScript Engine is no longer supported in Java 17.

Due to project constraints, I am not allowed to use third party libraries.

Is there a proper way to handle this in Java 17?

Answer 1

Java 15 removed Nashorn JavaScript Engine

So you need to use different script engine, as GraalVM

switch to the GraalVM JavaScript engine. First, add the required dependencies to your project.

<dependency>
  <groupId>org.graalvm.js</groupId>
  <artifactId>js</artifactId>
  <version>22.0.0</version>
</dependency>  
<dependency>
  <groupId>org.graalvm.js</groupId>
  <artifactId>js-scriptengine</artifactId>
  <version>22.0.0</version>
</dependency>

Then change the engine name to graal.js.

// Graal
ScriptEngine graalEngine = new ScriptEngineManager().getEngineByName("graal.js");
graalEngine.eval("print('Hello World!');");

You can check which engines available using

new ScriptEngineManager().getEngineFactories();

Or add different script engines to your project as velocity, jexl, groovy,...