Solving Enum Serialization Issues in Java: Custom Serializers Made Easy

Learn how to handle Java Enum serialization challenges when using APIs with custom serializers to get the desired output format.
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Understanding the Issue with Enum Serialization in Java

When working with Java Enums in a project, especially when they come from a compiled library, you might encounter some challenges. One common issue arises when serializing objects containing these Enums for API responses.

Imagine you have an Enum that you cannot modify, yet you need its serialized output to be in a specific format. For example, instead of returning:

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you want:

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This situation can be frustrating, especially when you don't have control over the Enum itself. However, there's a way to achieve this using a custom serializer in Java.

Your Attempt: Custom Serializer

In your initial attempt, you've implemented a custom serializer for your AttestationConveyancePreference Enum like so:

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The outcome you observed was:

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The Problem

What happened here is that your custom serializer is still wrapping the output in an additional object, hence the extra layer in the JSON response.

The Solution: Flattening the Object

To resolve this issue, the trick lies in how you write the serialized value using the JsonGenerator. Instead of wrapping the Enum value inside an object, you can directly write the value as a string.

Updated Custom Serializer Code

Here's the modified version of your serializer:

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Explanation of Changes

Resulting Output

After implementing these changes, the API response will now display:

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Conclusion

Naming conventions can sometimes lead to unexpected behavior in serialization processes when dealing with Enums in Java. However, understanding how to customize the serialization process with a custom serializer can help you manipulate the output format effectively.

Utilize the clean and simple solution provided above to achieve the desired results in your project without modifying any existing Enum classes.

So, next time you encounter a serialization issue with Enums, remember this approach to flatten your JSON output neatly!