Introduction

If you’re working with Micronaut and PostgreSQL, you’ve likely encountered the challenge of handling JSONB data types in your Micronaut entities. This blog aims to provide you with a clear solution to efficiently save and retrieve JSONB data within your Micronaut application.

The JSONB Challenge

As per the official documentation, you might have come across the recommendation to use the @TypeDef(type = DataType.JSON) annotation to handle JSONB data. However, you might have also encountered issues, such as the dreaded “Cannot encode parameter of type java.util.HashMap” error, which can be frustrating when you’re trying to work with JSONB data.

The Road to Resolution

I’ve encountered this issue myself, and I want to share the solution that worked for me. Let’s dive into the steps to resolve the JSONB data challenge in Micronaut entities.

Step 1: Entity Definition

Start by defining your Micronaut entity. In this example, we have an entity named TempJsonb that includes a property called data, which is of type JSONTemp.

@Introspected
@MappedEntity(value = "temp_jsonb")
data class TempJsonb(
    @field:Id @GeneratedValue var id: Long?,
    @TypeDef(type = DataType.JSON)
    var data: JSONTemp?,
)

Step 2: The JSONTemp Class

Create a separate data class, JSONTemp, to represent the JSONB data. This class will encapsulate the structure of your JSON data.

data class JSONTemp(
    var id: Int?
)

Step 3: The MappedProperty Solution

Here’s where the magic happens. Instead of using @TypeDef(type = DataType.JSON), employ the @MappedProperty annotation with type = DataType.JSON as shown below:

@Introspected
@MappedEntity(value = "temp_jsonb")
data class TempJsonb(
    @field:Id @GeneratedValue var id: Long?,
    @MappedProperty(type = DataType.JSON)
    var data: JSONTemp?,
)

Why MappedProperty?

Using @MappedProperty helps you overcome the “Cannot encode parameter” issue, ensuring a smooth data-saving process. Additionally, it simplifies data retrieval, making your code more robust and error-resistant. This approach even handles null values gracefully if your data column happens to be null.

Read also: Micronaut HTTP Request Interceptors: A Comprehensive Guide

Conclusion

Dealing with JSONB data types in Micronaut with PostgreSQL doesn’t have to be a stumbling block. By leveraging the @MappedProperty annotation with type = DataType.JSON, you can effectively save and retrieve JSONB data in your Micronaut entities. This solution ensures a seamless experience when working with JSONB data and contributes to the overall efficiency and reliability of your Micronaut application.