hibernate/hibernate-orm · error · UnsupportedOperationException

Support for model part type not yet implemented:

Error message

Support for model part type not yet implemented: 

What it means

The descriptive JSON serializer handles four model-part kinds: basic selectables, embedded attributes, entity-valued parts, and plural attributes. Any other ModelPart on the entity path - most commonly a @Any DiscriminatedAssociationAttributeMapping - throws UnsupportedOperationException with the part class name (or 'null').

Source

Thrown at hibernate-core/src/main/java/org/hibernate/type/descriptor/jdbc/spi/DescriptiveJsonGeneratingVisitor.java:124

		if ( modelPart instanceof SelectableMapping ) {
			writer.objectKey( modelPart.getPartName() );
			visit( modelPart.getMappedType(), value, options, writer );
		}
		else if ( modelPart instanceof EmbeddedAttributeMapping embeddedAttribute ) {
			writer.objectKey( embeddedAttribute.getAttributeName() );
			visit( embeddedAttribute.getMappedType(), value, options, writer );
		}
		else if ( modelPart instanceof EntityValuedModelPart entityPart ) {
			writer.objectKey( entityPart.getPartName() );
			visit( entityPart.getEntityMappingType(), value, options, writer );
		}
		else if ( modelPart instanceof PluralAttributeMapping plural ) {
			writer.objectKey( plural.getPartName() );
			serializePluralAttribute( value, plural, options, writer );
		}
		else {
			// could not handle model part, throw exception
			throw new UnsupportedOperationException(
					"Support for model part type not yet implemented: "
					+ (modelPart != null ? modelPart.getClass().getName() : "null")
			);
		}
	}

	private void serializePluralAttribute(
			Object value,
			PluralAttributeMapping plural,
			WrapperOptions options,
			JsonDocumentWriter writer) throws IOException {
		if ( handleNullOrLazy( value, writer ) ) {
			// nothing left to do
			return;
		}

		final CollectionPart element = plural.getElementDescriptor();
		final CollectionSemantics<?, ?> collectionSemantics = plural.getMappedType().getCollectionSemantics();

View on GitHub (pinned to fad1729dce)

Solutions

1. Replace the @Any mapping with a regular @ManyToOne to a mapped hierarchy.
2. Exclude entities carrying @Any from descriptive JSON export (select a projection instead).
3. Upgrade Hibernate: visitor coverage expands over versions; report the missing part class in a Jira issue.

Example fix

// before
@Any
@JoinColumn(name = "owner_id")
@AnyDiscriminator(DiscriminatorType.STRING)
@AnyKeyJavaType(Long.class)
private Serializable owner;   // -> Support for model part type not yet implemented
// after: plain association to a mapped hierarchy
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "owner_id")
private Party owner;

static void assertDescriptiveSerializable(Class<?> entity) {
    for (Field f : entity.getDeclaredFields()) {
        if (f.isAnnotationPresent(Any.class)) {
            throw new IllegalStateException(
                "@Any attribute not supported by descriptive JSON: " + f);
        }
    }
}

try {
    return resultsJsonSerializer.toJson(resultList);
} catch (UnsupportedOperationException ex) {
    if (ex.getMessage() != null && ex.getMessage().startsWith("Support for model part type")) {
        // entity carries an exotic part (e.g. @Any); fall back to a projection
        return serializeProjection(resultList);
    }
    throw ex;
}

When it happens

Trigger: Hibernate Assistant (or any consumer of DescriptiveJsonGeneratingVisitor) serializes an entity that contains an @Any or @AnyDiscriminator mapping, or another exotic model part not covered by the four supported kinds.

Common situations: Entities with polymorphic @Any references included in query results exported to JSON; enriching legacy models with any-style associations; new Hibernate versions adding model-part kinds the visitor has not learned yet.

Related errors

• Error serializing entity
• Failed to serialize JSON mapping
• Could not serialize array element
• Unsupported numeric type: {}
• array case should be treated at upper level

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/d0b5bc86fce81a88. Report an issue: GitHub.