hibernate/hibernate-orm · error · IllegalArgumentException

The {} class [{}] could not be instantiated

Error message

The {} class [{}] could not be instantiated

What it means

Thrown by EntityManagerFactoryBuilderImpl.loadSettingInstance() as an IllegalArgumentException when the class resolved from a setting exists but instanceClass.newInstance() fails - because the class has no accessible no-arg constructor, is abstract or an interface, or its constructor is non-public. The message names the expected type and the concrete class that failed to instantiate.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/jpa/boot/internal/EntityManagerFactoryBuilderImpl.java:1734

				try {
					instanceClass = (Class<? extends T>) Class.forName( className );
				}
				catch (ClassNotFoundException e) {
					throw new IllegalArgumentException( "Can't load class: " + className, e );
				}
			}
		}
		else {
			throw new IllegalArgumentException( "The provided " + settingName
					+ " setting value [" + settingValue + "] is not supported" );
		}

		if ( instanceClass != null ) {
			try {
				return instanceClass.newInstance();
			}
			catch (InstantiationException | IllegalAccessException e) {
				throw new IllegalArgumentException(
						"The " + clazz.getSimpleName() +" class [" + instanceClass + "] could not be instantiated",
						e
				);
			}
		}
		else {
			return null;
		}
	}

	/**
	 * Exposed to extensions: see Hibernate Reactive
	 */
	public StandardServiceRegistry getStandardServiceRegistry() {
		return standardServiceRegistry;
	}
}

View on GitHub (pinned to fad1729dce)

Solutions

  1. Add a public no-arg constructor to the configured class.
  2. If the class must be created with arguments, construct it yourself and pass the instance (or the Class) instead of the class name.
  3. Make sure the class is concrete and, if nested, static.
  4. If the constructor itself threw, check the cause for the underlying error in your initialization code.

Example fix

// before
public class MyInterceptor implements Interceptor {
    private final Registry registry;
    public MyInterceptor(Registry registry) { this.registry = registry; } // no no-arg ctor
}

// after
settings.put("hibernate.session_factory.interceptor", new MyInterceptor(registry)); // pass instance
Defensive patterns

Strategy: validation

Validate before calling

// verify constructibility before handing the class name to Hibernate
Class<?> c = Class.forName(fqcn);
if (Modifier.isAbstract(c.getModifiers()) || !Modifier.isPublic(c.getModifiers())) throw new IllegalStateException(fqcn + " must be a public concrete class");
c.getDeclaredConstructor().newInstance(); // dry-run the same reflective construction

Prevention

When it happens

Trigger: Configuring a class for a strategy setting that has only a constructor with arguments, is abstract, is a non-static inner class, or has a package-private/private no-arg constructor; newInstance() requires a public no-arg constructor.

Common situations: Handing a class that needs constructor injection (Spring beans) directly via a String setting; refactoring a helper class to abstract with concrete subclasses while the config still points at it; using an old implementation jar compiled against a different Hibernate API whose ctor throws.

Related errors

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/8844cf94079ce972. Report an issue: GitHub.