Nashorn is a lightweight JavaScript engine that ships with Java 8 and later versions. It allows developers to execute JavaScript code within the Java Virtual Machine (JVM), providing seamless integration between Java and JavaScript.

In this article, we will explore how to integrate Nashorn with existing Java frameworks and libraries, and leverage the power of JavaScript within your Java-based applications.

Table of Contents

1. Introduction to Nashorn
2. Integration with Java Frameworks
3. Using Nashorn with Libraries
4. Example: Spring Boot Integration
5. Conclusion

Introduction to Nashorn

Nashorn is a high-performance JavaScript engine developed by Oracle. It allows developers to execute JavaScript code directly on the JVM, eliminating the need for an external JavaScript runtime environment.

Nashorn provides seamless interoperability between Java and JavaScript, allowing you to call Java code from JavaScript and vice versa. It also provides access to Java APIs, making it easy to leverage existing Java libraries and frameworks within your JavaScript code.

Integration with Java Frameworks

One of the main benefits of using Nashorn is its ability to integrate with existing Java frameworks. Whether you are using Spring, JavaFX, or any other Java framework, you can easily incorporate Nashorn to execute JavaScript code within your application.

To integrate Nashorn with a Java framework, you typically need to follow these steps:

1. Import the necessary Nashorn classes and interfaces.
2. Create an instance of the Nashorn engine.
3. Execute JavaScript code using the Nashorn engine.
4. Access Java objects and APIs from your JavaScript code.
5. Optionally, bind Java objects to JavaScript variables for easier interaction.

By following these steps, you can seamlessly incorporate JavaScript functionality into your Java applications without the need for any additional setup.

Using Nashorn with Libraries

Another advantage of Nashorn is its ability to work with existing Java libraries. You can leverage the power of JavaScript to interact with Java libraries and make use of their functionality within your JavaScript code.

To use Nashorn with Java libraries, you need to:

1. Add the required Java library to your classpath.
2. Import the necessary Java classes into your JavaScript code.
3. Use the imported Java classes and methods within your JavaScript code.

For example, if you want to use a JSON processing library like Jackson with Nashorn, you can simply import the Jackson classes in your JavaScript code and perform JSON-related operations.

Example: Spring Boot Integration

Let’s take a practical example of integrating Nashorn with the Spring Boot framework.

First, include the necessary dependencies in your pom.xml file:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
</dependency>

Create a Java class, ScriptService, to handle the JavaScript execution:

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

public class ScriptService {
    
    public String executeScript(String script) throws ScriptException {
        ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
        ScriptEngine engine = scriptEngineManager.getEngineByName("nashorn");
        return (String) engine.eval(script);
    }
}

In your Spring Boot application, use ScriptService to execute JavaScript code:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MyApp {

    public static void main(String[] args) {
        SpringApplication.run(MyApp.class, args);

        ScriptService scriptService = new ScriptService();
        try {
            System.out.println(scriptService.executeScript("print('Hello, Nashorn!');"));
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

In the above example, we create an instance of ScriptService and execute a simple JavaScript code that prints “Hello, Nashorn!” to the console.

Conclusion

By integrating Nashorn with existing Java frameworks and libraries, you can unlock the full potential of JavaScript within your Java applications. Whether you want to enhance your Spring Boot app with JavaScript capabilities or leverage Java libraries from within JavaScript code, Nashorn provides a seamless integration pathway.

With its powerful interoperability, performance, and ability to access Java APIs, Nashorn empowers developers with the best of both worlds - Java and JavaScript.

#hashtags #Nashorn #Java