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Learn how to effectively register a custom JSON serializer for the `FastMoney` class, ensuring that monetary amounts are serialized correctly in your Jakarta EE applications.
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How to Create a Custom JSON Serializer for the FastMoney Class in JSR354 / Moneta

In modern Java applications, especially those that involve financial transactions, dealing with monetary amounts can sometimes be challenging. Specifically, when working with the Java Money API (JSR354) and its implementations like Moneta, serializers may not recognize complex types like FastMoney. This can lead to frustrating serialization errors when you try to convert objects into JSON format.

In this guide, we'll explore how to properly register a custom JSON serializer for the FastMoney class. By the end of this guide, you’ll be able to serialize monetary amounts effectively in your Jakarta EE applications.

The Problem

You have a class, such as InvoiceItem, that contains a FastMoney type representing monetary amounts. When you try to serialize this class into JSON, you encounter an Internal Server Error due to serialization issues. The error output references various serialization properties that fail to serialize correctly, leading to a cascade of exceptions.

Example of the Error

You might see errors in your log like this:

[[See Video to Reveal this Text or Code Snippet]]

This points towards an issue with how the FastMoney type is being handled during serialization. Therefore, you need to create a custom serializer tailored to the FastMoney class.

Solution: Creating a Custom Serializer

Step 1: Implement the Serializer

To resolve the issue, you need to implement a custom serializer for the FastMoney class. Here’s how to do it:

[[See Video to Reveal this Text or Code Snippet]]

In the code above:

We create a class FastMoneySerializer that implements JsonbSerializer<FastMoney>.

In the serialize method, we convert the FastMoney object to a string and write it to the JSON output.

Step 2: Register the Serializer in Your Class

Next, you need to annotate the FastMoney property in your InvoiceItem class to use the new serializer:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Ensure Proper Runtime Support

If you face any issues while running, ensure your runtime supports Jakarta EE properly. In this case, switching from Payara to GlassFish resolved the issues, as GlassFish fully supports Jakarta EE 9.

Example JSON Output

After implementing the custom serializer and ensuring the application runs without errors, your serialized JSON output for InvoiceItem should look like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Implementing a custom JSON serializer for the FastMoney class can significantly enhance your application's ability to handle monetary amounts correctly. By following the steps outlined in this guide, you can avoid serialization issues and ensure that your invoice data is represented accurately in JSON format.

Feel free to explore additional documentation related to Jakarta EE and JSON-B to enhance your understanding further!