Need help with Java Scripting API.

Greetings!

Ladys and Gentlemen, I need help with Java Scripting API.

I want to be able to manipulate fields and methods of instance of my class via embedded Javascript Rhino Engine. To do this I have written the following:

List<ScriptEngineFactory> factories = mgr.getEngineFactories(); ScriptEngineManager factory = new ScriptEngineManager(); ScriptEngine engine = factory.getEngineByName("JavaScript"); if ( pcode != null && (!pcode.isEmpty()) ) { MyClass mc = new MyClass(); try{ engine.put("mc", mc); engine.eval(print("mc.myfield")); } catch (Exception e) {e.printStackTrace();} }

Unfortunately this doesn't work: it prints 'undefined'. But if I replace MyClass with ArrayList for example, the sane scheme works. I mean that I can get the size of my ArrayList by ArrayList.size(), for example. If object of my own class is put into the Engine the situatuin is different: I can't use its fields and methods.
If I evaluate the following: 'for (i in mc) { print(i + '\n ') }' it prints all the methods that respond to Object class, but not methods from MyClass.

So, as far as I understand, the problem is with my own class. Probably I must import it somehow to the Engine? Please, help.

That code won't even compile; what code are you actually trying to run?

Right now you're printing the literal string "mc.myfield" (or would be if you were evaluating a string, which you're not, unless you didn't post all the relevant code).

Try correcting the code and following up.

OK, David, here is the full code with the same problem:


public class ScriptingExample { class MyClass { int myfield = 5; int getInt() {return 7;} } public void runExample() { ScriptEngineManager mgr = new ScriptEngineManager(); List<ScriptEngineFactory> factories = mgr.getEngineFactories(); ScriptEngineManager factory = new ScriptEngineManager(); ScriptEngine engine = factory.getEngineByName("JavaScript"); MyClass mc = new MyClass(); try{ engine.put("mc", mc); engine.eval("print(mc.myfield); print(mc.getInt())"); } catch (Exception e) {e.printStackTrace();} } }

When I run runExample function it prints "undefined" if I try to print only field, and the following error if I want to run the Java Object mc method getInt():

undefinedjavax.script.ScriptException: sun.org.mozilla.javascript.internal.EcmaError: TypeError: Cannot find function getInt. (<Unknown source>#1) in <Unknown source> at line number 1
at com.sun.script.javascript.RhinoScriptEngine.eval(Unknown Source)
at com.sun.script.javascript.RhinoScriptEngine.eval(Unknown Source)
at javax.script.AbstractScriptEngine.eval(Unknown Source)
at solutiondatabase.ScriptingExample.runExample(ScriptingExample.java:26)
at solutiondatabase.Main.main(Main.java:49)

Try making the fields and the method coderanch.

That's (mostly) correct--the scripting engine requires a publicly-accessible getter; it cannot directly access properties (at least it won't for me).

Thank you guys!

This works for functions. After I have marked my getInt function as public it started to work. Though I cannot get the 'myfield' anyway, if I make it public it throws an exception:

javax.script.ScriptException: sun.org.mozilla.javascript.internal.WrappedException: Wrapped java.lang.IllegalAccessException: Class sun.org.mozilla.javascript.internal.JavaMembers can not access a member of class solutiondatabase.ScriptingExample$MyClass with modifiers "public" (<Unknown source>#1) in <Unknown source> at line number 1
at com.sun.script.javascript.RhinoScriptEngine.eval(Unknown Source)
at com.sun.script.javascript.RhinoScriptEngine.eval(Unknown Source)
at javax.script.AbstractScriptEngine.eval(Unknown Source)
at solutiondatabase.ScriptingExample.runExample(ScriptingExample.java:33)
at solutiondatabase.Main.main(Main.java:49)

Otherwise the return is 'undefined'.

As David said, you apparently need public getters and setters for accessing fields, in line with how JavaBeans work.