hibernate/hibernate-orm · error · NullPointerException

null merge and managed entities are not supported by

Error message

null merge and managed entities are not supported by 

What it means

Error "null merge and managed entities are not supported by " thrown in hibernate/hibernate-orm.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/event/spi/MergeContext.java:223

	 * Associates the specified merge entity with the specified managed entity in this MergeContext.
	 * If this MergeContext already contains a cross-reference for {@code mergeEntity} when this
	 * method is called, then <code>managedEntity</code> must be the same as what is already associated
	 * with {@code mergeEntity}.
	 *
	 * @param mergeEntity the merge entity; must be non-null
	 * @param managedEntity the managed entity; must be non-null
	 * @param isOperatedOn indicates if the merge operation is performed on the mergeEntity.
	 *
	 * @return previous managed entity associated with specified merge entity, or null if
	 * there was no mapping for mergeEntity.
	 * @throws NullPointerException if mergeEntity or managedEntity is null
	 * @throws IllegalArgumentException if {@code managedEntity} is not the same as the previous
	 * managed entity associated with {@code mergeEntity}
	 * @throws IllegalStateException if internal cross-references are out of sync,
	 */
	public @Nullable Object put(@Nonnull Object mergeEntity, @Nonnull Object managedEntity, boolean isOperatedOn) {
		if ( mergeEntity == null || managedEntity == null ) {
			throw new NullPointerException( "null merge and managed entities are not supported by " + getClass().getName() );
		}

		Object oldManagedEntity = mergeToManagedEntityXref.put( mergeEntity, managedEntity );
		Boolean oldOperatedOn = mergeEntityToOperatedOnFlagMap.put( mergeEntity, isOperatedOn );
		// If managedEntity already corresponds with a different merge entity, that means
		// that there are multiple entities being merged that correspond with managedEntity.
		// In the following, oldMergeEntity will be replaced with mergeEntity in managedToMergeEntityXref.
		Object oldMergeEntity = managedToMergeEntityXref.put( managedEntity, mergeEntity );

		if ( oldManagedEntity == null ) {
			// this is a new mapping for mergeEntity in mergeToManagedEntityXref
			if  ( oldMergeEntity != null ) {
				// oldMergeEntity was a different merge entity with the same corresponding managed entity;
				entityCopyObserver.entityCopyDetected( managedEntity, mergeEntity, oldMergeEntity, session );
			}
			if ( oldOperatedOn != null ) {
				throw new IllegalStateException(
						"MergeContext#mergeEntityToOperatedOnFlagMap contains a merge entity " + printEntity( mergeEntity )

View on GitHub (pinned to fad1729dce)

Solutions

1. Ensure both the merge (detached) entity and its managed copy are non-null before operating on the merge context.

When it happens

Trigger: Thrown when a null key or value is put into the merge-to-managed mapping of a MergeContext.

Common situations: Typical situations: merging a graph containing null elements; cascade-merge reaching a null association or collection element.

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/c3105b1bedb633b8. Report an issue: GitHub.