Expanding Java Classes and Replacing Methods with Multiple Parameters in ES4X/Graal

Question

Expanding Java Classes and Replacing Methods with Multiple Parameters in ES4X/Graal

I am currently facing a challenge in my JavaScript project using ES4X/Graal, where I need to extend a Java class. This Java class has methods with overloaded parameters that I must override. While I understand how to call a specific Java method by specifying the type in square brackets, it seems that there is no clear way to specify parameter types when overriding based on the Graal/Oracle/Nashorn documentation. For example:

package com.mycomp;

class A {
    public void method(String parameter) {...}
    public void method(int parameter) {...}
}

In JavaScript, calling these methods can be done as follows:

var a = Java.type("com.mycomp.A");

a["method(String)"]("Some string parameter")
a["method(int)"](42)
a.method(stringOrIntParam)

However, during extension, the options are limited:

var ClassAFromJava = Java.type("com.mycom.A");
var MyJavaScriptClassA = Java.extend(ClassAFromJava, {
    method: function(stringOrIntParam) {...}
}

I desire the ability to extend only one of the "method(...)" methods. Additionally, how would this work for overloaded methods with distinct return types?

Thank you!

javascript java graalvm graaljs

Answer 1

Answer №1

Utilizing the sj4js framework enables you to achieve all of this.

This specific scenario is slightly adjusted from the official documentation...

public class TestObject extends JsProxyObject {
    
    // constructor containing the property 
    public TestObject (String name) {
        super ();
        
        this.name = name;
        
        // initialization of the proxy object
        init(this);
    }

    // mandatory override method for the proxy object functionality 
    @Override
    protected Object newInstance() {
        return new TestClass(this.name);
    }

    // method with a String parameter
    public String method (String s) {
        return "String";
    }

    // method with an int parameter
    public String method (int i) {
        return "42";
    }
}

You can interact with this object as if it were a JS object, and the library handles selecting the appropriate method.

try (JScriptEngine engine = new JScriptEngine()) {
    engine.addObject("test", new TestClass("123"));
            
    // invoking the method with the String parameter will 
    // execute the corresponding java method
    engine.exec("test.method('123')");
    // returns "String"

    // invoking the method with the int parameter will 
    // execute the relevant java method
    engine.exec("test.method(123)");
    // returns "42"
}

Answer 2

Utilizing the sj4js framework enables you to achieve all of this.

This specific scenario is slightly adjusted from the official documentation...

public class TestObject extends JsProxyObject {
    
    // constructor containing the property 
    public TestObject (String name) {
        super ();
        
        this.name = name;
        
        // initialization of the proxy object
        init(this);
    }

    // mandatory override method for the proxy object functionality 
    @Override
    protected Object newInstance() {
        return new TestClass(this.name);
    }

    // method with a String parameter
    public String method (String s) {
        return "String";
    }

    // method with an int parameter
    public String method (int i) {
        return "42";
    }
}

You can interact with this object as if it were a JS object, and the library handles selecting the appropriate method.

try (JScriptEngine engine = new JScriptEngine()) {
    engine.addObject("test", new TestClass("123"));
            
    // invoking the method with the String parameter will 
    // execute the corresponding java method
    engine.exec("test.method('123')");
    // returns "String"

    // invoking the method with the int parameter will 
    // execute the relevant java method
    engine.exec("test.method(123)");
    // returns "42"
}

Expanding Java Classes and Replacing Methods with Multiple Parameters in ES4X/Graal

Answer №1

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