Using Nashorn with different Java versions

Nashorn has two distribution channels:

• it ships as a built-in component of OpenJDK-based Java distributions between Java versions 8 to 14. It no longer ships starting with Java 15 and is not actively developed.
• it is available as a standalone library distributed on Maven Central. The standalone library is usable with Java 11 and above and is actively developed.

We'll refer to these as "built-in" and "standalone" versions of Nashorn. The table below summarizes what versions of Java can use what version of Nashorn:

Java	Built-in	Standalone
7 and earlier	⛔	⛔
8-10	✅	⛔
11-14	✅	✅
15 and later	⛔	✅

Using Nashorn on Java 11 to 14

Some consideration is necessary if you want to distribute an application that uses Nashorn and it should run both on Java 11-14 and Java 15+ versions. You can bundle standalone Nashorn with your application, but note that when running on Java versions between 11-14, built-in Nashorn will also be available to it. Which one gets used depends on several factors:

• If you create your script engine using Nashorn APIs, you can unambiguously select which one you want by addressing the relevant package;
  • you can create an engine factory for the built-in version by instantiating jdk.nashorn.api.scripting.NashornScriptEngineFactory and
  • an engine factory for the standalone version by instantiating org.openjdk.nashorn.api.scripting.NashornScriptEngineFactory. If you use explicit APIs, we recommend you use standalone Nashorn in this case as your application is then future-proof for Java 15 and beyond and leave built-in Nashorn inactive.
• If you create your script engine using javax.script.* APIs, i.e. with an expression like ScriptEngineManager.getEngineByName("nashorn") then you will get:
  • standalone Nashorn, if you loaded Nashorn as a module through the --module-path option as it gets precedence there, but
  • built-in Nashorn, if standalone Nashorn is loaded on the ordinary classpath.