With the popularity of serverless computing on the rise, developers are exploring different approaches to implement serverless functions. One option is to use the Nashorn JavaScript engine, which is included with the Java Development Kit (JDK) starting from JDK 8.

Nashorn provides a seamless integration between JavaScript and Java, making it an ideal choice for implementing serverless functions that require access to Java libraries and APIs. In this article, we’ll explore how to get started with Nashorn and implement serverless functions using this powerful tool.

What is Nashorn?

Nashorn is a JavaScript engine developed by Oracle and included with the JDK. It allows you to execute JavaScript code within a Java environment, providing access to Java APIs and libraries. This makes Nashorn an attractive choice for implementing serverless functions that require both JavaScript and Java functionality.

Getting Started with Nashorn

To get started with Nashorn, you first need to install the JDK if you haven’t already. Once installed, you can use the jjs command-line tool to execute JavaScript code using Nashorn.

Here’s a simple example to demonstrate how to execute JavaScript code with Nashorn:

// hello.js
print("Hello, world!");

To run this script, save it to a file called hello.js and execute the following command in your command-line interface:

jjs hello.js

You should see the output “Hello, world!” printed to the console.

Implementing Serverless Functions with Nashorn

Now that we have a basic understanding of Nashorn, let’s see how we can implement serverless functions using this JavaScript engine.

First, we need to define our serverless function as a JavaScript script. We can define the function using the function keyword and provide the necessary logic within the function body. Here’s an example of a simple serverless function that calculates the sum of two numbers:

// sum.js
function sum(a, b) {
    return a + b;
}

// Export the function so it can be invoked from Java
exports.sum = sum;

Next, we need to create a Java class that will invoke our serverless function. We can use the Nashorn engine to execute the JavaScript code and invoke the serverless function from within our Java code. Here’s an example of how the Java class can look like:

import javax.script.*;

public class FunctionInvoker {
    public static void main(String[] args) throws Exception {
        // Create a new instance of the Nashorn engine
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");

        // Load the serverless function script
        engine.eval(new java.io.FileReader("sum.js"));

        // Invoke the serverless function
        Invocable invocable = (Invocable) engine;
        int result = (int) invocable.invokeFunction("sum", 3, 4);

        // Print the result
        System.out.println("Result: " + result);
    }
}

To run this code, make sure you have the sum.js script in the same directory as the FunctionInvoker.java file, and compile and execute the FunctionInvoker class using your Java compiler. You should see the output “Result: 7” printed to the console.

This example demonstrates how you can integrate JavaScript serverless functions with Java using Nashorn. You can expand on this concept by adding more complex functionality to your serverless functions and leveraging the capabilities of both JavaScript and Java in your applications.

Conclusion

Nashorn provides a powerful and flexible way to implement serverless functions using JavaScript within a Java environment. Its seamless integration with Java libraries and APIs allows developers to leverage the strengths of both JavaScript and Java to build scalable and efficient serverless applications.

By following the steps outlined in this article, you can get started with Nashorn and implement serverless functions that take advantage of JavaScript’s dynamic capabilities and Java’s extensive ecosystem.

#developer #serverless