# JSR 223 javax.script API

version 3.0.21

| JSR-223 is a standard API for calling scripting frameworks in Java. It is available since Java 6 and aims at providing a common framework for calling multiple languages from Java. Groovy provides its own richer integration mechanisms, and if you don’t plan to use multiple languages in the same application, it is recommended that you use the Groovy integration mechanisms instead of the limited JSR-223 API.

Here is how you need to initialize the JSR-223 engine to talk to Groovy from Java:

    import javax.script.ScriptEngine;
    import javax.script.ScriptEngineManager;
    import javax.script.ScriptException;
    ...
    ScriptEngineManager factory = new ScriptEngineManager();
    ScriptEngine engine = factory.getEngineByName("groovy");

Then you can execute Groovy scripts easily:

    Integer sum = (Integer) engine.eval("(1..10).sum()");
    assertEquals(new Integer(55), sum);

It is also possible to share variables:

    engine.put("first", "HELLO");
    engine.put("second", "world");
    String result = (String) engine.eval("first.toLowerCase() + ' ' + second.toUpperCase()");
    assertEquals("hello WORLD", result);

This next example illustrates calling an invokable function:

    import javax.script.Invocable;
    ...
    ScriptEngineManager factory = new ScriptEngineManager();
    ScriptEngine engine = factory.getEngineByName("groovy");
    String fact = "def factorial(n) { n == 1 ? 1 : n * factorial(n - 1) }";
    engine.eval(fact);
    Invocable inv = (Invocable) engine;
    Object[] params = {5};
    Object result = inv.invokeFunction("factorial", params);
    assertEquals(new Integer(120), result);

The engine keeps per default hard references to the script functions. To change this you should set a engine level scoped attribute to the script context of the name `#jsr223.groovy.engine.keep.globals` with a String being `phantom` to use phantom references, `weak` to use weak references or `soft` to use soft references - casing is ignored. Any other string will cause the use of hard references.