hibernate/hibernate-orm · error · UnsupportedOperationException

Not a Map-valued attribute node

Error message

Not a Map-valued attribute node

What it means

addKeySubgraph() is implemented only on MapAttributeNodeImpl — the node kind created for Map-valued attributes. Calling it on a singular node or a non-Map collection node hits the base-class implementation and throws UnsupportedOperationException.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/graph/internal/AttributeNodeImpl.java:213

		return valueSubgraph;
	}

	@Override
	@Nonnull
	public SubGraphImplementor<J> addSingularSubgraph() {
		throw new UnsupportedOperationException("Not a singular attribute node");
	}

	@Override
	@Nonnull
	public SubGraphImplementor<E> addElementSubgraph() {
		throw new UnsupportedOperationException( "Not a collection-valued attribute node" );
	}

	@Override
	@Nonnull
	public SubGraphImplementor<K> addKeySubgraph() {
		throw new UnsupportedOperationException( "Not a Map-valued attribute node" );
	}

	protected void checkToOne() {
		final Attribute.PersistentAttributeType attributeType = attribute.getPersistentAttributeType();
		if ( attributeType != MANY_TO_ONE && attributeType != ONE_TO_ONE && attributeType != EMBEDDED ) {
			throw new CannotContainSubGraphException( "Attribute '" + attribute.getName() + "' is not a to-one association" );
		}
	}

	protected void checkToMany() {
		final Attribute.PersistentAttributeType attributeType = attribute.getPersistentAttributeType();
		if ( attributeType != MANY_TO_MANY && attributeType != ONE_TO_MANY ) {
			throw new CannotContainSubGraphException( "Attribute '" + attribute.getName() + "' is not a to-many association" );
		}
	}

	protected <T> ManagedDomainType<T> asManagedType(DomainType<T> domainType) {
		if ( domainType instanceof ManagedDomainType<T> managedDomainType ) {

View on GitHub (pinned to fad1729dce)

Solutions

1. Use addKeySubgraph() only on Map attributes; fetch Map values with addElementSubgraph()
2. For non-map collections use addElementSubgraph()
3. Guard the call with attr instanceof MapAttribute before invoking

Example fix

// before
graph.addAttributeNode("tags").addKeySubgraph(); // tags is List<String> → throws

// after — key subgraphs exist only for Map attributes
graph.addAttributeNode("settings")   // Map<Language, Setting>
     .addKeySubgraph();                // Language key subgraph
graph.addAttributeNode("settings")
     .addElementSubgraph().addAttributeNode("value");

if (isMap(node.getAttribute())) {
    node.addKeySubgraph();      // keys
    node.addElementSubgraph();  // values
}

static boolean isMap(Attribute<?, ?> attr) {
    return attr instanceof jakarta.persistence.metamodel.MapAttribute<?, ?, ?>;
}

When it happens

Trigger: node.addKeySubgraph() where the attribute is a @OneToMany/@ManyToOne/List/Set/basic — anything that is not a persistent java.util.Map attribute.

Common situations: Adding key-fetching logic to graphs of collections that were Maps in an earlier iteration of the model; generic graph code that calls all three subgraph variants unconditionally.

Related errors

• Not a singular attribute node
• Not a collection-valued attribute node
• No node for attribute: {}
• Duplicate named entity graph '%s'
• The 'root' parameter of the @NamedEntityGraph should be pass

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/2a3ab12854aba435. Report an issue: GitHub.