Hibernate schema validation fails with JPA event publication registry

[vkarppinen]

When using spring.jpa.hibernate.ddl-auto=validate with the JPA event publication registry and the documented PostgreSQL schema, Hibernate fails with:
Schema validation: column defined as not-null in the database, but nullable in model - [event_type] in table [event_publication]

The documented schema defines columns like event_type, listener_id, etc. as NOT NULL, but Hibernate sees the entity model as nullable and fails validation.

Is there a recommended way to use schema validation with the JPA event publication registry?

Versions:
Spring Modulith: 2.0.2
Spring Boot: 4.0.2
Hibernate: 7.2.1.Final

[odrotbohm]

The first paragraph of the quoted section states that the schemas are intended for use with the JDBC:

The JDBC-based event publication registry support expects the following database schemas to be present in the database. If you would like Spring Modulith to create the schema for you, set the application property spring.modulith.events.jdbc-schema-initialization.enabled to true.

While we generally try to keep the delta as minimal as possible, we do not verify the JDBC schemas to work with every possible configuration option in Hibernate. Generally speaking, we recommend using the JDBC-based event publication registry even with JPA-based applications, as the JPA one doesn't add any extra value except terminological symmetry. In fact, we're considering deprecating the JPA implementation entirely.

That said, I'll use this ticket to tweak the mappings of our JPA entity type to more closely align with the schemas used in JDBC.

[vkarppinen]

Thanks for the clarification 👍

We will look into migrating to the JDBC-based registry. Feel free to close this issue.

[ghferrari]

@odrotbohm I'd like to add two comments to this issue.

• First, if you use the Spring Initializr and add Spring Modulith and Spring Data JPA as dependencies, it automatically adds these two lines:

  implementation("org.springframework.modulith:spring-modulith-starter-core")
  implementation("org.springframework.modulith:spring-modulith-starter-jpa")

So, if you're wondering why some people (including me) seem to be using the JPA package by default and perhaps without being fully aware of it, that may be because it's being included by default there.

Secondly, if the spring-modulith-events-jpa package is not compatible with the database schema that is defined by spring-modulith-events-jdbc, then I can only report my own feeling that that is a bug. I may be misremembering but I think I saw it mentioned somewhere that it should be possible to use both the JPA and JDBC events packages together, but if you're saying there's no guarantee that the schema that's initialized by the JDBC package is compatible with the Hibernate entities defined in the JPA package, then that doesn't seem to be possible after all. Setting ddl-auto=validate is hardly an exotic edge case.

[odrotbohm]

@ghferrari – That's great feedback, thanks. IIRC I've always claimed that the JDBC event publication registry works fine in an otherwise JPA-based application. I never (intentionally) claimed that the JPA- and JDBC-based registries were interchangeable, but I can see that the devil is in the details here.

Flipping to include the JDBC registry for new Modulith applications even if they're using JPA is a great idea indeed.

[odrotbohm]

Thanks for the clarification 👍

We will look into migrating to the JDBC-based registry. Feel free to close this issue.

I'd like to use this ticket to change the Hibernate mappings to more closely resemble what the documented schemas look like. This also makes sense because users of relational database migration tools will likely be inspired to use these schemas as a starting point for their JPA applications, and we can resolve some friction for those as well.