Serializing Map Keys with BigDecimal Using Jackson

Learn how to serialize a `Map` with `BigDecimal` keys using Jackson, ensuring correct deserialization. This guide covers custom serializers and provides code examples for implementation.
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This video is based on the question https://stackoverflow.com/q/68313450/ asked by the user 'Hussein Zaraket' ( https://stackoverflow.com/u/13135207/ ) and on the answer https://stackoverflow.com/a/68360655/ provided by the user 'Michał Ziober' ( https://stackoverflow.com/u/51591/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When working with Java’s Map collections, you may frequently encounter the need to serialize these maps into JSON format. One particular issue arises when keys of type BigDecimal are serialized as strings, which can lead to complications during deserialization. In this guide, we’ll explore how to serialize a Map<BigDecimal, BigDecimal> using Jackson while ensuring that the keys retain their data type as BigDecimal, rather than being converted to strings.

The Problem

Using Jackson, serialize a Map<BigDecimal, BigDecimal> with default typing enabled can lead to unexpected behavior. For example, running the following snippet:

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Results in:

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Notice how the keys (i.e., 1 and 10) have been serialized as strings instead of their original BigDecimal types. This discrepancy poses a challenge when we try to deserialize the JSON back into our original Map structure.

The Solution: Custom Serializers and Deserializers

To properly serialize BigDecimal keys, we can use custom serializers and deserializers. Here’s how to implement a solution that maintains the integrity of BigDecimal keys.

Step 1: Create a Custom Key Serializer

You need to define a serializer that handles BigDecimal keys correctly. Here’s an example:

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Step 2: Create a Custom Key Deserializer

Next, define how to deserialize those keys back into BigDecimal:

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Step 3: Register Custom Serializers and Deserializers

Finally, you need to register your custom serializers and deserializers with an ObjectMapper:

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Conclusion

By implementing custom serializers and deserializers with Jackson, you can effectively manage BigDecimal keys in your maps, ensuring they serialize and deserialize correctly as BigDecimal rather than default to strings. This approach maintains the type integrity of your data, facilitating smoother data manipulation and transfer.

Explore this customized solution in your own projects, and say goodbye to those pesky serialization issues!