How do you configure Jackson for a Spring Boot application?

Table of Contents

• Introduction
• Default Jackson Configuration in Spring Boot
  • Jackson Dependency (Maven)
  • Jackson Dependency (Gradle)
• Customizing Jackson in Spring Boot
  • 1. Customizing **ObjectMapper** Bean
    • Example: Custom ObjectMapper Configuration
  • 2. Customizing Date Formats
    • Example: Custom Date Format Configuration
  • 3. Adding Custom Serializers and Deserializers
    • Example: Registering Custom Serializers and Deserializers
  • 4. Configuring Jackson Features with **application.properties** or **application.yml**
    • Example: Configure Jackson Date Format in application.properties
    • Example: Configure Jackson Features in application.yml
  • 5. Disabling Default Jackson Features
    • Example: Disable FAIL_ON_EMPTY_BEANS
• Practical Example: Full Configuration with ObjectMapper
• Conclusion

Introduction

Jackson is the default library used by Spring Boot for JSON processing, providing powerful features for serializing Java objects into JSON and deserializing JSON back into Java objects. Although Spring Boot automatically configures Jackson for you, there are times when you may need to customize Jackson's behavior, such as altering default serialization settings, configuring the ObjectMapper, or changing how specific classes are serialized.

In this guide, we will explore how to configure Jackson in a Spring Boot application, covering the most common configuration scenarios.

Default Jackson Configuration in Spring Boot

Spring Boot automatically configures Jackson by default, and all you need to do is include the Jackson dependency in your pom.xml or build.gradle file. Spring Boot uses Jackson2ObjectMapperBuilder to configure the ObjectMapper bean.

Jackson Dependency (Maven)

If you’re using Maven, Spring Boot includes the Jackson dependency by default. However, you can explicitly add the Jackson dependency like this:

Jackson Dependency (Gradle)

For Gradle, the Jackson dependency is included in Spring Boot’s starter web module. If needed, you can manually add it:

Once the dependency is included, Spring Boot automatically configures Jackson for JSON serialization and deserialization, and you can start using @RequestBody, @ResponseBody, or @RestController for automatic JSON processing.

Customizing Jackson in Spring Boot

Even though Spring Boot automatically configures Jackson, you can override the default settings by customizing the ObjectMapper or providing specific configuration classes. Below are some of the most common Jackson configuration tasks.

1. Customizing **ObjectMapper** Bean

You can define your own ObjectMapper bean in Spring Boot if you need to customize Jackson's behavior globally (e.g., changing default date formats, adding custom serializers or deserializers).

Example: Custom ObjectMapper Configuration

In this example:

• We define an ObjectMapper bean that enables pretty printing for JSON output (e.g., human-readable format with indentation).
• This ObjectMapper will be used globally across your Spring Boot application to customize how JSON is serialized.

2. Customizing Date Formats

You might want to configure a global date format, especially when dealing with Date or LocalDate objects. By default, Jackson uses ISO-8601 format for dates. You can customize this format globally by configuring the ObjectMapper.

Example: Custom Date Format Configuration

In this example:

• The ObjectMapper is customized to use the date format dd-MM-yyyy for all Date objects during serialization and deserialization.

3. Adding Custom Serializers and Deserializers

You can also add custom serializers or deserializers for specific Java types globally by registering them in the ObjectMapper configuration.

Example: Registering Custom Serializers and Deserializers

Here:

• We define a custom serializer for MyCustomClass by creating a MyCustomSerializer class.
• We register this custom serializer to the ObjectMapper globally, meaning it will be used for all instances of MyCustomClass.

4. Configuring Jackson Features with **application.properties** or **application.yml**

You can configure various Jackson features without writing Java code by adding properties in your application.properties or application.yml file.

Example: Configure Jackson Date Format in application.properties

This configuration will globally set the date format for Jackson's serialization and deserialization.

Example: Configure Jackson Features in application.yml

5. Disabling Default Jackson Features

Sometimes, you may want to disable default Jackson features, such as FAIL_ON_EMPTY_BEANS (to avoid errors when serializing empty beans) or WRITE_DATES_AS_TIMESTAMPS (to disable timestamps for date fields).

Example: Disable FAIL_ON_EMPTY_BEANS

This will prevent Jackson from throwing an error when it encounters an empty Java bean during serialization.

Practical Example: Full Configuration with ObjectMapper

Let’s combine everything into a full example. This Spring Boot application configures Jackson to:

• Use a custom date format.
• Pretty-print JSON output.
• Register custom serializers and deserializers.

Conclusion

Jackson is automatically configured in Spring Boot, but Spring Boot provides ample flexibility for you to customize its behavior when necessary. You can:

• Customize global serialization settings like date formats, pretty printing, or inclusion/exclusion of properties.
• Register custom serializers and deserializers for specific Java types.
• Configure Jackson features either through Java configuration (ObjectMapper) or using application properties (application.properties or application.yml).

With these configurations, you can fine-tune how Jackson processes JSON data in your Spring Boot applications, making it flexible enough to handle any JSON-related requirement.