spring-projects/spring-framework · error · NullValueInNestedPathException

Invalid property '{propertyName}' of bean class [{beanClass.

Error message

Invalid property '{propertyName}' of bean class [{beanClass.getName()}]: Could not determine property type for auto-growing a default value

What it means

Thrown as NullValueInNestedPathException by createDefaultPropertyValue at AbstractNestablePropertyAccessor.java:871 when auto-grow is enabled but getPropertyTypeDescriptor() returns null for the property, so Spring cannot determine which class to instantiate as the default value. It is purely an auto-grow configuration/introspection failure, not a null data problem.

Source

Thrown at spring-beans/src/main/java/org/springframework/beans/AbstractNestablePropertyAccessor.java:871

			if (logger.isTraceEnabled()) {
				logger.trace("Using cached nested property accessor for property '" + canonicalName + "'");
			}
		}
		return nestedPa;
	}

	private Object setDefaultValue(PropertyTokenHolder tokens) {
		PropertyValue pv = createDefaultPropertyValue(tokens);
		setPropertyValue(tokens, pv);
		Object defaultValue = getPropertyValue(tokens);
		Assert.state(defaultValue != null, "Default value must not be null");
		return defaultValue;
	}

	private PropertyValue createDefaultPropertyValue(PropertyTokenHolder tokens) {
		TypeDescriptor desc = getPropertyTypeDescriptor(tokens.canonicalName);
		if (desc == null) {
			throw new NullValueInNestedPathException(getRootClass(), this.nestedPath + tokens.canonicalName,
					"Could not determine property type for auto-growing a default value");
		}
		Object defaultValue = newValue(desc.getType(), desc, tokens.canonicalName);
		return new PropertyValue(tokens.canonicalName, defaultValue);
	}

	private Object newValue(Class<?> type, @Nullable TypeDescriptor desc, String name) {
		try {
			if (type.isArray()) {
				return createArray(type);
			}
			else if (Collection.class.isAssignableFrom(type)) {
				TypeDescriptor elementDesc = (desc != null ? desc.getElementTypeDescriptor() : null);
				return CollectionFactory.createCollection(type, (elementDesc != null ? elementDesc.getType() : null), 16);
			}
			else if (Map.class.isAssignableFrom(type)) {
				TypeDescriptor keyDesc = (desc != null ? desc.getMapKeyTypeDescriptor() : null);
				return CollectionFactory.createMap(type, (keyDesc != null ? keyDesc.getType() : null), 16);

View on GitHub (pinned to 69bf83ad71)

Solutions

Disable auto-grow for that path or give the property a concrete declared type with proper getter/setter.
Add explicit getter/setter and field type so getPropertyTypeDescriptor resolves to a real class.
Pre-initialize the nested object yourself instead of relying on auto-grow.
Register a custom property editor / ConversionService if the type is non-standard.

Example fix

// before: auto-grow cannot infer type
private Object details;
wrapper.setAutoGrowNestedPaths(true);

// after: concrete, introspectable type
private Details details = new Details();

Defensive patterns

Strategy: validation

Validate before calling

// Only enable auto-grow for fully introspectable types
BeanWrapper w = new BeanWrapperImpl(target);
if (w.getPropertyTypeDescriptor("details") != null) {
    w.setAutoGrowNestedPaths(true);
} else {
    // initialize manually; do not rely on auto-grow
    ((MyBean) target).setDetails(new Details());
}

Type guard

static boolean autoGrowSafe(BeanWrapper w, String path) {
    return w.getPropertyTypeDescriptor(path) != null;
}

Try / catch

try {
    wrapper.setAutoGrowNestedPaths(true);
    wrapper.getPropertyValue("details.x");
} catch (NullValueInNestedPathException ex) {
    if (ex.getMessage().contains("Could not determine property type")) {
        // not a data problem: introspect the type manually
        throw new IllegalStateException("cannot auto-grow " + ex.getPropertyName(), ex);
    }
    throw ex;
}

Prevention

Ensure auto-grown properties have concrete declared types with getters/setters.
Prefer explicit initialization over auto-grow for non-introspectable types.
Test auto-grow against each nested type in a unit test.
Avoid Object/Map-typed fields where you expect auto-grow to materialize a bean.

When it happens

Trigger: setAutoGrowNestedPaths(true) is set, then a nested path is traversed whose target property has no readable/writable accessor and no resolvable TypeDescriptor (e.g. a property that exists only as a Map/Collection index with no generic info, or a synthetic property the BeanWrapper cannot introspect). getPropertyTypeDescriptor returns null and setDefaultValue is invoked.

Common situations: Auto-growing into an untyped Map/Object property; binding against a dynamic bean with no proper getters/setters; auto-growing a property whose declaring class has reflection issues (introspection partially failed); misconfigured @ConfigurationProperties with auto-grow on a field Spring cannot introspect.

Related errors

AI-assisted analysis of spring-projects/spring-framework@69bf83ad71 (2026-08-09). Data as JSON: /api/errors/6bc7bdbfa830b611. Report an issue: GitHub.