example using rhino's JavaAdapter

Question

Hi

Can someone provide me an example on how to extend a java class in java script using Rhino's java adapter ?

Answer 1

Depends on what you want to inherit. I find that if I use the JavaScript prototype for object “definitions” I get the static methods of Java objects only:

function test() {
  this.hello = function() {
    for(var i in this) {
      println(i);
    }
  };
}
test.prototype= com.acme.app.TestClass; // use your class with static methods
// see the inheritance in action:
var testInstance=new test();
test.hello();

However, JavaScript allows you to do prototype assignments on object instances as well, so you could use a function like this, and get a more Java-like inheritance behaviour:

function test(baseInstance) {
  var obj = new function() {
    this.hello=function() { 
      for(var i in this) { 
        println(i); 
      }
    };
  };
  obj.prototype=baseInstance; // inherit from baseInstance.
}

// see the thing in action:
var testInstance=test(new com.acme.TestClass()); // provide your base type
testInstance.hello();

Or use a function (e.g. init) similar to the above function in the object itself:

function test() {
  this.init=function(baseInstance) {
    this.prototype=baseInstance;
  };
  this.hello=function() {
    for(var i in this) {
      println(i);
    }
  };
}

var testInstance=new test();
println(typeof(testInstance.prototype)); // is null or undefined
testInstance.init(new com.acme.TestClass()); //  inherit from base object

// see it in action:
println(typeof(testInstance.prototype)); // is now com.acme.TestClass
testInstance.hello();

Answer 2

Since I am not a 100% sure that by Java Adapter you mean what I think it is, Java interfaces and such can be created with property lists (name = function()):

var runnable = new java.lang.Runnable({
   run: function() { println('hello world!'); } // uses methodName: implementationFunction convention
};
java.awt.EventQueue.invokeLater(runnable); // test it

Or alternatively for single-method things like that:

function runnableFunc() { println('hello world!'); }
var runnable = new java.lang.Runnable(runnableFunc); // use function name
java.awt.EventQueue.invokeLater(runnable); // test it