Spring Boot 4.0.1 + GraalVM: processAot Fails with hibernate.hbm2ddl.auto=update (Requires AOT Task Configuration Workaround)

[mingchiuli]

hibernate-core version: 7.2.0.FINAL

Description

When using Spring Boot 4.0.1 with GraalVM native image compilation (AOT processing), configuring Hibernate's hbm2ddl.auto=update triggers a fatal error during the processAot Gradle task. The error occurs because Hibernate attempts to access a JDBC connection during AOT processing (for schema migration) but no connection is available at this stage.

Environment

• Spring Boot: 4.0.1
• Hibernate: 7.2.0.Final (bundled with Spring Boot 4.0.1)
• GraalVM: Any version (reproducible with latest GraalVM CE 21/25)
• Build Tool: Gradle (Kotlin/Groovy DSL)
• JPA Configuration: spring.jpa.properties.hibernate.hbm2ddl.auto=update

Reproduction Steps

1. Create a new Spring Boot 4.0.1 project with Spring Data JPA dependency.
2. Add the following configuration to application.yml/application.properties:

   spring:
     jpa:
       properties:
         hibernate:
           hbm2ddl:
             auto: update

3. Add a simple JPA entity and repository (e.g., User entity + UserRepository).
4. Run GraalVM AOT processing via Gradle: ./gradlew processAot (or build native image with ./gradlew nativeCompile).

Expected Behavior

AOT processing completes successfully, and the native image can be built without errors.

Actual Behavior

The processAot task fails with an AotProcessingException caused by a Hibernate PersistenceException ("Unable to build Hibernate SessionFactory") and a root cause of "The application must supply JDBC connections".

Full Error Stack Trace Snippet

> Task :processAot FAILED

Exception in thread "main" org.springframework.beans.factory.aot.AotProcessingException: Error executing 'org.springframework.beans.factory.aot.BeanRegistrationsAotProcessor': Unable to build Hibernate SessionFactory  [persistence unit: AotMetamodel] 
    at org.springframework.context.aot.BeanFactoryInitializationAotContributions.processAheadOfTime(BeanFactoryInitializationAotContributions.java:86)
    ...
Caused by: jakarta.persistence.PersistenceException: Unable to build Hibernate SessionFactory  [persistence unit: AotMetamodel] 
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1461)
    ...
Caused by: java.lang.UnsupportedOperationException: The application must supply JDBC connections
    at org.hibernate.engine.jdbc.connections.internal.UserSuppliedConnectionProviderImpl.getConnection(UserSuppliedConnectionProviderImpl.java:39)
    ...

Workaround

Adding the following Gradle configuration to disable schema generation during AOT processing resolves the issue:

// Gradle Kotlin DSL
tasks.withType<ProcessAot>().configureEach {
    systemProperty("spring.jpa.properties.jakarta.persistence.schema-generation.database.action", "none")
}

Root Cause Analysis

During AOT processing, Spring Data JPA attempts to initialize a Hibernate SessionFactory for metamodel generation. When hibernate.hbm2ddl.auto=update is set, Hibernate tries to connect to the database to perform schema migration—but no JDBC connection is available in the AOT processing context (this is a build-time step, not runtime).

The workaround disables schema generation only during AOT processing by setting jakarta.persistence.schema-generation.database.action=none, which prevents Hibernate from attempting a database connection during build time.

Request

• Fix Spring Boot 4.0.1 to handle hibernate.hbm2ddl.auto=update gracefully during AOT processing (without requiring manual task configuration).
• Automatically disable Hibernate schema generation during AOT processing (or provide a built-in property to control this behavior).
• Update Spring Boot documentation to note this limitation/workaround for GraalVM + Hibernate users.

Additional Context

This issue is specific to Spring Boot 4.0.1 (and possibly 4.0.x) – earlier versions (e.g., 3.2.x) may not exhibit this behavior due to differences in AOT processing for JPA. The workaround is functional but non-intuitive for users migrating to Spring Boot 4.0.x with GraalVM.