Make My Java Program Supports Dynamic Language (2)

However, when you are thinking about script language support, the first thing you would be concerned might probably not be the performance, but the Java language interoperable. As I mentioned in the previous POST, JDK 6’s script engine only support engine.eval() method. If you have experience with BeanShell, you might probably be comfortable with it. Yes, I can feed the method with a script and return an Object so that I can go further. How about the parameters? OK, there are Bindings I can use.

Invocable

The only access to your script via ScriptEngine is .eval(), however, some ScriptEngine implements another interface:

Invocable

Code Example 7: You can use the Invocable interface to call specific methods in a script.

  jsEngine.eval("function sayHello() {" +
                "  println('Hello, world!');" +
                "}");
  Invocable invocableEngine = (Invocable) jsEngine;
  invocableEngine.invokeFunction("sayHello");

Just look at the Invocable interface’s description:

Method Summary
<T> T	getInterface(Class<T> clasz)            Returns an implementation of an interface using functions compiled in the interpreter.
<T> T	getInterface(Object thiz, Class<T> clasz)            Returns an implementation of an interface using member functions of a scripting object compiled in the interpreter.
Object	invokeFunction(String name, Object... args)            Used to call top-level procedures and functions defined in scripts.
Object	invokeMethod(Object thiz, String name, Object... args)            Calls a method on a script object compiled during a previous script execution, which is retained in the state of the ScriptEngine.

It looks nice. It’s much better than using the stupid eval() and binding methods in ScriptEngine.