Java Nashorn JavaScript Engine

Nashorn is a lightweight JavaScript engine that allows developers to run JavaScript code directly within Java applications. It is part of the Java Development Kit (JDK) starting from Java 8.

Key Concepts

• Integration: Nashorn enables seamless integration between Java and JavaScript, allowing Java applications to execute JavaScript code and vice versa.
• Performance: It is designed to provide better performance than its predecessor, Rhino, and supports the ECMAScript 5.1 standard.
• Scripting API: Nashorn uses the Java Scripting API (JSR 223) to facilitate the execution of JavaScript in Java applications.

Features

• Scripting Support: Easily run JavaScript scripts from Java code.
• Java Object Access: JavaScript can access and manipulate Java objects.
• JavaScript-to-Java Calls: You can call Java methods from JavaScript and vice versa.

Basic Usage

Running JavaScript in Java

You can run JavaScript code in a Java application using the ScriptEngine interface. Here’s a simple example:

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class NashornExample {
    public static void main(String[] args) {
        // Create a ScriptEngineManager
        ScriptEngineManager manager = new ScriptEngineManager();
        
        // Create a Nashorn script engine
        ScriptEngine engine = manager.getEngineByName("nashorn");
        
        // Execute a JavaScript script
        try {
            engine.eval("print('Hello from Nashorn!');");
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

Accessing Java Objects

You can also access Java objects in your JavaScript code. Here’s an example:

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

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

        // Create a Java object
        String message = "Hello from Java!";
        
        // Pass the Java object to JavaScript
        engine.put("javaMessage", message);
        
        // Access the Java object in JavaScript
        try {
            engine.eval("print(javaMessage);");
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

Conclusion

Nashorn offers a powerful way to integrate JavaScript into Java applications, making it easier for developers to leverage both languages effectively. With its ability to execute scripts and interact with Java objects, Nashorn opens up new possibilities for Java development.