What causes "Parameter %d of function 'xmlforest()' is not named" in hibernate/hibernate-orm?

Alias every argument of xmlforest(): select xmlforest(p.name as "name", p.age as "age") from Person p

hibernate/hibernate-orm · error · FunctionArgumentException

Parameter %d of function 'xmlforest()' is not named

Error message

Parameter %d of function 'xmlforest()' is not named

What it means

The 'xmlforest()' HQL function must emit one XML element per argument, and each element needs a tag name, so every argument has to be an aliased (named) expression (SqmNamedExpression). During SQM validation XmlForestFunction iterates the arguments and throws FunctionArgumentException with the 0-based parameter position when argument i carries no alias. This fails at query translation time, before SQL generation.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/dialect/function/xml/XmlForestFunction.java:46

 * Standard xmlforest function.
 */
public class XmlForestFunction extends AbstractSqmSelfRenderingFunctionDescriptor {

	public XmlForestFunction(TypeConfiguration typeConfiguration) {
		super(
				"xmlforest",
				FunctionKind.NORMAL,
				StandardArgumentsValidators.composite(
						StandardArgumentsValidators.min( 1 ),
						new ArgumentsValidator() {
							@Override
							public void validate(
									List<? extends SqmTypedNode<?>> arguments,
									String functionName,
									BindingContext bindingContext) {
								for ( int i = 0; i < arguments.size(); i++ ) {
									if ( !( arguments.get( i ) instanceof SqmNamedExpression<?> namedExpression ) ) {
										throw new FunctionArgumentException(
												String.format(
														"Parameter %d of function 'xmlforest()' is not named",
														i
												)
										);
									}
									if ( !XmlHelper.isValidXmlName( namedExpression.getName() ) ) {
										throw new FunctionArgumentException(
												String.format(
														"Invalid XML element name passed to 'xmlforest()': %s",
														namedExpression.getName()
												)
										);
									}
								}
							}

						}

View on GitHub (pinned to fad1729dce)

Solutions

Alias every argument of xmlforest(): select xmlforest(p.name as "name", p.age as "age") from Person p
If you build HQL dynamically, assert each contributed fragment inside xmlforest(...) contains ' as <alias>'
If you do not need per-element names, use a different construction (e.g. xmlelement or client-side mapping) since xmlforest fundamentally requires names

Example fix

// before
select xmlforest(p.name, p.age) from Person p

// after
select xmlforest(p.name as "name", p.age as "age") from Person p

Defensive patterns

Strategy: validation

Validate before calling

// Before building xmlforest(...) fragments, ensure every argument is aliased
boolean allAliased = args.stream().allMatch(a -> a.contains(" as "));
if (!allAliased) {
    throw new IllegalArgumentException("every xmlforest() argument needs an alias, e.g. p.name as \"name\"");
}

Try / catch

try {
    return session.createQuery(hql, String.class).list();
}
catch (FunctionArgumentException e) {
    // e.getMessage() contains the 0-based parameter index
    throw new IllegalArgumentException("xmlforest() argument not aliased: " + e.getMessage(), e);
}

Prevention

Treat xmlforest() like a projection: every expression gets an alias that becomes the XML tag name
Lint generated HQL in CI with a parser or a regex check for unaliased arguments inside xmlforest(...)
Keep xmlforest calls in one query-building module so aliasing cannot be forgotten at call sites

When it happens

Trigger: Calling xmlforest() with plain, unaliased expressions: select xmlforest(p.name, p.age) from Person p - argument 0 ('p.name') is not named, so 'Parameter 0 of function 'xmlforest()' is not named' is thrown. Also happens when a dynamic query builder omits the 'as alias' clause for one of several arguments.

Common situations: Copying native SQL/XML 'xmlforest()' calls into HQL (SQL dialects can derive names from column labels, Hibernate cannot); refactoring a select list and dropping aliases; criteria/HQL generated from reflection over field names without aliasing.

Related errors

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/2445b72cdce10e38. Report an issue: GitHub.