Nashorn, a JavaScript engine in Java 8 and earlier versions, provides seamless interoperability between Java and JavaScript code. This allows developers to leverage the power of both languages within the same application. In this blog post, we will explore how to achieve interoperability between Java and JavaScript in Nashorn.

Table of Contents

• Introduction to Nashorn
• Accessing Java from JavaScript
• Accessing JavaScript from Java
• Conclusion

Introduction to Nashorn

Nashorn is a modern JavaScript runtime developed for the Java Virtual Machine (JVM). With Nashorn, you can execute JavaScript code within a Java application. Nashorn aims to provide better performance compared to earlier JavaScript engines such as Rhino.

Nashorn supports ECMAScript 5.1 specification, including many of its features, such as scopes, functions, arrays, regular expressions, and more. It seamlessly integrates with existing Java libraries and provides interoperability between Java and JavaScript code.

Accessing Java from JavaScript

Nashorn allows you to access Java classes, methods, and fields from JavaScript code. By importing Java packages and classes, you can create Java objects, invoke Java methods, and access Java fields.

Here’s a simple example that demonstrates accessing a Java class from JavaScript:

import javax.swing.JOptionPane;

public class HelloWorld {
    public static void sayHello(String name) {
        JOptionPane.showMessageDialog(null, "Hello, " + name + "!");
    }
}

To invoke the sayHello method from JavaScript, you can use the Java.type function to create an instance of the HelloWorld Java class and call the method:

var HelloWorld = Java.type('HelloWorld');
HelloWorld.sayHello('John');

This will display a message dialog saying “Hello, John!”.

Accessing JavaScript from Java

Nashorn also allows Java code to access and execute JavaScript code. You can evaluate JavaScript expressions, invoke JavaScript functions, and access JavaScript objects and properties from your Java code.

Here’s an example that demonstrates accessing JavaScript code from Java:

import javax.script.*;

public class JavaScriptAccess {
    public static void main(String[] args) throws ScriptException {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("nashorn");

        engine.eval("var message = 'Hello, World!';");
        engine.eval("print(message);");
    }
}

In this example, we create a ScriptEngine using ScriptEngineManager and evaluate JavaScript code using the eval method. We define a message variable in JavaScript and print it using the print function.

Conclusion

Nashorn provides powerful interoperability between Java and JavaScript, allowing developers to leverage the strengths of both languages within the same application. By accessing Java from JavaScript and accessing JavaScript from Java, you can create more flexible and efficient applications.

With Nashorn’s seamless integration, it becomes easier to utilize existing Java libraries and frameworks in JavaScript code and vice versa. This opens up a wide range of possibilities for developers to build robust and scalable applications.

#java #javascript