hibernate/hibernate-orm · error · RuntimeException

Couldn't load or define class [{className}]

Error message

Couldn't load or define class [{className}]

What it means

Error "Couldn't load or define class [{className}]" thrown in hibernate/hibernate-orm.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/bytecode/internal/bytebuddy/ByteBuddyState.java:200

			if ( result.getClassLoader() == referenceClass.getClassLoader() ) {
				return result;
			}
		}
		catch (ClassNotFoundException e) {
			// Ignore
		}
		try {
			return make( makeClassFunction.apply( byteBuddy, new FixedNamingStrategy( className ) ) )
					.load( referenceClass.getClassLoader(),
							resolveClassLoadingStrategy( referenceClass ) )
					.getLoaded();
		}
		catch (LinkageError e) {
			try {
				return referenceClass.getClassLoader().loadClass( className );
			}
			catch (ClassNotFoundException ex) {
				throw new RuntimeException( "Couldn't load or define class [" + className + "]", e );
			}
		}
	}

	private Class<?> load(Class<?> referenceClass, TypeCache<TypeCache.SimpleKey> cache,
			TypeCache.SimpleKey cacheKey, Function<ByteBuddy, DynamicType.Builder<?>> makeProxyFunction) {
		return cache.findOrInsert(
				referenceClass.getClassLoader(),
				cacheKey,
				() -> make( makeProxyFunction.apply( byteBuddy ) )
						.load( referenceClass.getClassLoader(),
								resolveClassLoadingStrategy( referenceClass ) )
						.getLoaded(),
				cache
		);
	}

	public Unloaded<?> make(Function<ByteBuddy, DynamicType.Builder<?>> makeProxyFunction) {

View on GitHub (pinned to fad1729dce)

Solutions

1. Open and export the entity package to Hibernate ORM (module-info: 'opens com.acme.model to org.hibernate.orm.core') or move enhancement to build time.

Example fix

Open and export the entity package to Hibernate ORM (module-info: 'opens com.acme.model to org.hibernate.orm.core') or move enhancement to build time.

When it happens

Trigger: Bytecode enhancement, proxy creation, or lazy interception is applied to an incompatible class or configuration.

Common situations: Build-time enhancement with module-system restrictions, mismatched Hibernate versions between build and runtime, or hibernate.bytecode.provider=none with a model that needs proxies.

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/7841416ff858677f. Report an issue: GitHub.