Why Are Entity Properties with @Id Not Marshalled to JSON in Spring Boot with Spring Data Rest?

Why are entity properties annotated with @Id not serialized to JSON when using Spring Data Rest after migrating to Spring Boot?

When migrating an application to Spring Boot while using Spring Data Rest, one common issue developers encounter is that entity properties annotated with `@Id` are not included in the JSON response. This behavior can cause confusion, especially when expecting certain fields to be serialized and included in the API response.

import javax.persistence.Entity;
import javax.persistence.Id;
import com.fasterxml.jackson.annotation.JsonProperty;

@Entity
public class MyEntity {
    @Id
    @JsonProperty
    private Long id;
    // Other properties and getters/setters
}

Causes

• Spring Data Rest by default configures how entities are represented in JSON using the backing repository and may alter serialization based on certain configurations.
• The serialization process may be influenced by the presence of specific annotations or configurations that dictate what fields are marshalled to JSON.
• If your entities are using Lombok or other libraries that manipulate bytecode, these could also affect how the `@Id` properties are handled.

Solutions

• Verify the configuration of `Spring Data Rest` and ensure that you are not explicitly excluding the `@Id` properties in your repository configuration.
• Add `@JsonProperty` annotation to the `@Id` fields in your entity class to explicitly instruct the serializer to include these fields in the output.
• Check if your entity class is correctly annotated with `@Entity` and that the getters for the `@Id` properties are public.

Mistake: Failing to ensure the repository is configured properly for Spring Data Rest.

Solution: Check the specific repository annotations to confirm that they do not alter the default behavior of mashing `@Id` fields.

Mistake: Not providing necessary JSON serialization annotations to entity classes.

Solution: Use `@JsonProperty` to specify each entity field that needs to be serialized.