java rhino 例子

Rhino: JavaScript in Java

Rhino is an open-source JavaScript engine written entirely in Java. It provides an environment for executing JavaScript code within Java applications. Rhino allows developers to embed JavaScript functionality into their Java applications, extending the power and flexibility of the application.

Introduction to Rhino

Rhino is based on the ECMAScript Language Specification, also known as JavaScript. It provides developers with a way to execute JavaScript code in a Java Virtual Machine (JVM) environment. Rhino can be used as a standalone interpreter for JavaScript programs or as an embedded scripting engine within Java applications.

One of the main advantages of using Rhino is the ability to seamlessly integrate JavaScript code with existing Java code. This allows developers to leverage the strengths of both languages and build powerful applications that are easy to develop and maintain.

Getting Started with Rhino

To get started with Rhino, you need to download the Rhino library and include it in your Java project. You can download the Rhino library from the official Mozilla website. Once you have included the library in your project, you can start using Rhino in your Java code.

Let's take a look at a simple example to understand how Rhino works:

import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.Scriptable;

public class RhinoExample {
    public static void main(String[] args) {
        // Create a new context
        Context context = Context.enter();

        try {
            // Create a new scope
            Scriptable scope = context.initStandardObjects();

            // Define a JavaScript function
            String jsFunction = "function multiply(a, b) { return a * b; }";

            // Evaluate the JavaScript function in the scope
            context.evaluateString(scope, jsFunction, "jsFunction", 1, null);

            // Get the JavaScript function object
            Object multiplyFunction = scope.get("multiply", scope);

            // Cast the JavaScript function object to a Java interface
            Function multiply = (Function) multiplyFunction;

            // Call the JavaScript function with arguments
            Object result = multiply.call(context, scope, scope, new Object[]{2, 3});

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

        } finally {
            // Exit the context
            Context.exit();
        }
    }
}

In this example, we create a new Rhino context and a scope. We define a JavaScript function multiply that takes two arguments and returns their product. We evaluate the JavaScript function in the scope and retrieve the JavaScript function object. We then cast the JavaScript function object to a Java interface Function and call the JavaScript function with arguments. Finally, we print the result.

Integrating Rhino in Java Applications

Rhino can be used to extend the functionality of Java applications by providing a flexible scripting environment. You can expose Java objects and functions to the embedded JavaScript code and vice versa.

Let's see how we can integrate Rhino in a Java application using a simple example:

import org.mozilla.javascript.Context;
import org.mozilla.javascript.NativeJavaObject;
import org.mozilla.javascript.Scriptable;

public class RhinoIntegrationExample {
    public static void main(String[] args) {
        // Create a new context
        Context context = Context.enter();

        try {
            // Create a new scope
            Scriptable scope = context.initStandardObjects();

            // Define a Java object and expose it to the JavaScript code
            Object javaObject = new JavaObject();
            Object wrappedJavaObject = Context.javaToJS(javaObject, scope);
            ScriptableObject.putProperty(scope, "javaObject", wrappedJavaObject);

            // Define a JavaScript function that calls the Java object
            String jsFunction = "function callJavaObject() { javaObject.someMethod(); }";

            // Evaluate the JavaScript function in the scope
            context.evaluateString(scope, jsFunction, "jsFunction", 1, null);

            // Call the JavaScript function
            context.evaluateString(scope, "callJavaObject();", "callJavaObject", 1, null);

        } finally {
            // Exit the context
            Context.exit();
        }
    }
}

public class JavaObject {
    public void someMethod() {
        System.out.println("Java object method called");
    }
}

In this example, we create a Rhino context and a scope. We define a Java object JavaObject and expose it to the JavaScript code using Context.javaToJS method. We define a JavaScript function callJavaObject that calls the Java object's someMethod. We evaluate the JavaScript function in the scope and call it using context.evaluateString.

Conclusion

Rhino provides an excellent way to integrate JavaScript functionality into Java applications. It allows developers to leverage the power of both languages and build robust and flexible applications. With Rhino, you can seamlessly execute JavaScript code within a Java environment, opening up endless possibilities for application development.

Rhino is widely used in various domains, including web development, automation, and testing. Its ease of use and extensive documentation make it an ideal choice for developers looking to add JavaScript capabilities to their Java projects.

So why not give Rhino a try and explore the possibilities of JavaScript in Java? Happy coding!