I wanted to play with Micronaut 2.5 and the latest changes in Micronaut Data allowing to work with immutable Kotlin data classes.

Can I use a non-nullable Long as identifier when creating an entity and what happens when Micronaut Data JDBC repository saves this entity to the DB?

The answer: An entity is instantiated with some random id (for ex. Long.Max). When you call the JDBC repository save method it will return a copy of the object, but the id will match the DB primary key.

• JDK 11
• Docker

• Micronaut 2.5.1
• Micronaut Gradle Plugin
• Kotlin
• Java 11
• Testcontainers with Postgresql
• Flyway

Most interesting things can be found in the MicronautDataIdExampleTest.kt file.

• Immutable Kotlin data class annotated with MappedEntity with id generated by a DB sequence
• For testcontainer configuration see application-test.yml