Java Nashorn is a JavaScript engine that is included in the Java Development Kit (JDK). It allows developers to execute JavaScript code within a Java environment. When working with Java Nashorn, it is important to understand how to handle exceptions that may occur in the JavaScript code.

Try-Catch Blocks

One way to handle exceptions in Java Nashorn is by using try-catch blocks. This allows you to catch and handle any exceptions that are thrown in the JavaScript code.

try {
    // JavaScript code that may throw an exception
} catch (e) {
    // Handle the exception
}

In the catch block, you can specify a variable (in this case e) to represent the thrown exception. You can then use this variable to perform any necessary error handling or logging.

Throwing Exceptions from Java

Another way to handle exceptions in Java Nashorn is by throwing Java exceptions from within your JavaScript code. This allows you to catch and handle these exceptions in your Java code.

try {
    // JavaScript code that may throw an exception
} catch (e) {
    throw new JavaException("An error occurred", e);
}

In this example, the JavaScript code may throw an exception, and if it does, a new JavaException is thrown from the catch block. This JavaException can then be caught and handled in the surrounding Java code.

Accessing Java Exceptions in JavaScript

You can also catch and handle Java exceptions that are thrown in the Java code from within your JavaScript code. To do this, you can use the javaException property of the caught exception.

try {
    // Java code that may throw an exception
} catch (e) {
    if (typeof e.javaException !== 'undefined') {
        // Handle the Java exception
    } else {
        // Handle the JavaScript exception
    }
}

In this example, if the caught exception has a javaException property, it means that a Java exception was thrown in the Java code. You can then handle the Java exception accordingly. If the javaException property is not defined, it means that a JavaScript exception was thrown.

Conclusion

Handling exceptions in Java Nashorn is similar to handling exceptions in regular JavaScript. You can use try-catch blocks to catch and handle exceptions in the JavaScript code, and you can also throw Java exceptions from within your JavaScript code and catch them in your Java code. By understanding these techniques, you’ll be able to effectively handle and manage exceptions when working with Java Nashorn.

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