hibernate/hibernate-orm · critical · HibernateException

Multiple active MetadataBuilder definitions were discovered

Error message

Multiple active MetadataBuilder definitions were discovered : <activeFactoryNames>

What it means

MetadataSources.getMetadataBuilder() discovers MetadataBuilderFactory implementations via the JDK ServiceLoader and asks each to provide a builder. Only one factory may be active: when two or more return a builder, Hibernate cannot choose between competing metadata pipelines and throws HibernateException listing the active factory class names. In practice this means the classpath carries competing Hibernate boot providers — usually two hibernate-core versions.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/boot/MetadataSources.java:203

						.loadJavaServices( MetadataBuilderFactory.class );

		MetadataBuilder builder = null;
		List<String> activeFactoryNames = null;

		for ( MetadataBuilderFactory discoveredBuilderFactory : discoveredBuilderFactories) {
			final MetadataBuilder returnedBuilder =
					discoveredBuilderFactory.getMetadataBuilder( this, defaultBuilder );
			if ( returnedBuilder != null ) {
				if ( activeFactoryNames == null ) {
					activeFactoryNames = new ArrayList<>();
				}
				activeFactoryNames.add( discoveredBuilderFactory.getClass().getName() );
				builder = returnedBuilder;
			}
		}

		if ( activeFactoryNames != null && activeFactoryNames.size() > 1 ) {
			throw new HibernateException(
					"Multiple active MetadataBuilder definitions were discovered : " +
							String.join(", ", activeFactoryNames)
			);
		}

		return builder != null ? builder : defaultBuilder;
	}

	/**
	 * Shorthand form of calling {@link #getMetadataBuilder()} and using its
	 * {@link MetadataBuilder#build()} method in cases where the application
	 * wants to accept the defaults.
	 *
	 * @return The built metadata.
	 */
	public Metadata buildMetadata() {
		return getMetadataBuilder().build();
	}

View on GitHub (pinned to fad1729dce)

Solutions

Run mvn dependency:tree / gradle dependencies, find both paths pulling hibernate-core, and exclude the older one so exactly one version ships.
On application servers, mark hibernate-core provided and use the server's Hibernate instead of bundling your own.
If you register a custom MetadataBuilderFactory, make it return null (decline) unless it must take over.

Example fix

<!-- before: legacy-lib transitively pulls hibernate-core 6.4 alongside your 6.6 -->
<!-- after -->
<dependency>
  <groupId>com.example</groupId>
  <artifactId>legacy-lib</artifactId>
  <exclusions>
    <exclusion>
      <groupId>org.hibernate</groupId>
      <artifactId>hibernate-core</artifactId>
    </exclusion>
  </exclusions>
</dependency>

Defensive patterns

Strategy: validation

Validate before calling

ClassLoader cl = Thread.currentThread().getContextClassLoader();
Enumeration<URL> locations = cl.getResources("org/hibernate/boot/MetadataSources.class");
if (Collections.list(locations).size() > 1) {
    throw new IllegalStateException("Multiple hibernate-core jars on classpath: "
            + Collections.list(locations));
}

Try / catch

Catch org.hibernate.HibernateException around getMetadataBuilder(); when the message starts with 'Multiple active MetadataBuilder definitions', print the factory names and the hibernate-core jar locations, then fix the classpath.

Prevention

Run mvn dependency:tree / gradle dependencies after every Hibernate upgrade and keep exactly one hibernate-core.
Use provided scope for container-managed Hibernate.
Beware uber-jar/shading merges of META-INF/services files.

When it happens

Trigger: Two jars both providing a MetadataBuilderFactory service (hibernate-core 6.x and 6.y both present via transitive dependencies, a shaded uber-jar, or a bundled WAR plus server-provided Hibernate) where every discovered factory returns a non-null builder.

Common situations: Upgrading Hibernate while the old jar lingers in EAR/lib or a server module; dependency mediation leaving two versions; shading merges META-INF/services entries; a custom factory from another framework competing with the built-in one.

Related errors

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/e6b583b9109f48c3. Report an issue: GitHub.