How do you implement custom serialization and deserialization in Spring Boot?

Table of Contents

• Introduction
• Implementing Custom Serialization and Deserialization in Spring Boot
  • 1. Creating a Custom Serializer
    • Example:
  • 2. Registering the Custom Serializer with Jackson
    • Example:
  • 3. Creating a Custom Deserializer
    • Example:
  • 4. Registering the Custom Deserializer with Jackson
    • Example:
  • 5. Using Custom Serialization and Deserialization
    • Example: Using the Custom Serializer and Deserializer
  • 6. Testing Your Custom Serialization and Deserialization
    • Example: Controller
• Conclusion

Introduction

In Spring Boot, JSON serialization and deserialization are crucial for mapping Java objects to JSON and vice versa. By default, Spring Boot uses the Jackson library for this task. However, in some cases, you might need more control over how objects are serialized or deserialized, such as when dealing with complex data structures or applying specific formatting rules. Implementing custom serialization and deserialization in Spring Boot can be done using custom serializers and deserializers in Jackson.

Implementing Custom Serialization and Deserialization in Spring Boot

1. Creating a Custom Serializer

A custom serializer in Jackson allows you to define how a Java object is converted to JSON. You can implement a custom serializer by extending JsonSerializer and overriding the serialize method.

Example:

Let’s create a custom serializer for a Person class that converts the person's birthdate to a formatted string.

Here, the CustomDateSerializer formats the Date object to a string in the format yyyy-MM-dd.

2. Registering the Custom Serializer with Jackson

After creating the custom serializer, you need to register it with Jackson. You can do this by creating a Jackson2ObjectMapperBuilder bean and customizing the ObjectMapper.

Example:

By registering the CustomDateSerializer with Jackson, any Date field in your Java objects will now be serialized using the custom format.

3. Creating a Custom Deserializer

Deserialization is the process of converting JSON back into Java objects. You can implement a custom deserializer by extending JsonDeserializer and overriding the deserialize method.

Example:

Now, let’s create a custom deserializer that reads a formatted date string (yyyy-MM-dd) and converts it back into a Date object.

This custom deserializer converts the date string in the format yyyy-MM-dd into a Date object.

4. Registering the Custom Deserializer with Jackson

Just like with serializers, you need to register the custom deserializer with Jackson. You can register it in the same way by using a SimpleModule.

Example:

This ensures that any JSON string in the format yyyy-MM-dd is correctly deserialized into a Date object.

5. Using Custom Serialization and Deserialization

Now, you can use your custom serialization and deserialization logic in your application. For instance, consider a Person class with a birthdate field that you want to serialize and deserialize.

Example: Using the Custom Serializer and Deserializer

You can now serialize and deserialize the Person object using the custom format you’ve defined for the birthdate.

6. Testing Your Custom Serialization and Deserialization

You can test the custom serialization and deserialization in your Spring Boot application by creating an endpoint or using a unit test to verify the behavior.

Example: Controller

When you access the /person endpoint, the birthdate will be serialized in the custom format (yyyy-MM-dd), and when deserialized, it will convert back to a Date object.

Conclusion

Custom serialization and deserialization in Spring Boot allow you to control how your objects are represented as JSON and how JSON is mapped back to Java objects. By using Jackson’s JsonSerializer and JsonDeserializer interfaces, you can implement complex conversion logic that fits your needs. Whether it's formatting dates, transforming data, or applying custom rules, implementing these features enhances the flexibility of your Spring Boot application and its interaction with JSON data.