Ways to invoke Java function using Javascript (Client-side)

I have a Java Swing application that handles the User Interface, but requires JavaScript files for hardware testing. The application calls a JavaScript engine to execute functions using the `InvokeFunction()` method.

Currently, I am utilizing the LabJack API which is specifically designed for Java and not JavaScript. While I have already implemented a working code in Java, I now need JavaScript to trigger this Java method.

Is there a way to invoke a Java function from JavaScript code? In other words, is there an equivalent approach in JavaScript?

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("JavaScript");

// Define JavaScript code as a String
String script1 = (String)"function hello(name) {print ('Hello, ' + name);}";

// Evaluate the script
engine.eval(script1);

Invocable inv = (Invocable) engine;

inv.invokeFunction("hello", "Scripting!!" );

To provide further context, let's consider a practical example. Suppose the JavaScript code interacts with an IR Toy to send IR data to a light. My task is to capture the number of flashes generated by the light, a process that can only be achieved through Java implementation. Therefore, I require a way to call the Java method from JavaScript so that both functionalities can be integrated into a single test.

javascriptjava

Answer №1

In the transition to Java 8, the JavaScript engine was switched from Rhino to Nashorn, resulting in a change in how Java objects are created.

A versatile method that is applicable to both engines involves passing a Java object to the script using Bindings. This allows the JavaScript code to access and utilize any public method of the object.

Alternatively, the object can be passed as a parameter directly into the script.

EXAMPLE utilizing Bindings

ArrayList<String> myList = new ArrayList<>();
myList.add("Hello");

Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
bindings.put("myList", myList);

String script1 = "function hello(name) {" +
                 "  myList.add(name);" +
                 "  print(myList);" +
                 "}";
engine.eval(script1);

Invocable inv = (Invocable)engine;
inv.invokeFunction("hello", "Scripting!!" );

EXAMPLE utilizing parameters

String script1 = "function hello(myList, name) {" +
                 "  myList.add(name);" +
                 "  print(myList);" +
                 "}";
engine.eval(script1);

ArrayList<String> myList = new ArrayList<>();
myList.add("Hello");

Invocable inv = (Invocable)engine;
inv.invokeFunction("hello", myList, "Scripting!!");

OUTPUT

[Hello, Scripting!!]

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