spring-projects/spring-framework · error · InvalidPropertyException

Cannot get element with index {index} from Collection of siz

Error message

Cannot get element with index {index} from Collection of size {coll.size()}, accessed using property path '{propertyName}'

What it means

Raised in the Iterable/Collection branch of getPropertyValue(PropertyTokenHolder) when the value is a Collection and the requested index is < 0 or >= coll.size(). Spring throws InvalidPropertyException naming the index, the size, and the path. Unlike List, a generic Collection has no positional get(), so an out-of-range index is rejected up front before iterating.

Source

Thrown at spring-beans/src/main/java/org/springframework/beans/AbstractNestablePropertyAccessor.java:650

					else if (value instanceof List list) {
						int index = Integer.parseInt(key);
						growCollectionIfNecessary(list, index, indexedPropertyName.toString(), ph, i + 1);
						value = list.get(index);
					}
					else if (value instanceof Map map) {
						Class<?> mapKeyType = ph.getResolvableType().getNested(i + 1).asMap().resolveGeneric(0);
						// IMPORTANT: Do not pass full property name in here - property editors
						// must not kick in for map keys but rather only for map values.
						TypeDescriptor typeDescriptor = TypeDescriptor.valueOf(mapKeyType);
						Object convertedMapKey = convertIfNecessary(null, null, key, mapKeyType, typeDescriptor);
						value = map.get(convertedMapKey);
					}
					else if (value instanceof Iterable iterable) {
						// Apply index to Iterator in case of a Set/Collection/Iterable.
						int index = Integer.parseInt(key);
						if (value instanceof Collection<?> coll) {
							if (index < 0 || index >= coll.size()) {
								throw new InvalidPropertyException(getRootClass(), this.nestedPath + propertyName,
										"Cannot get element with index " + index + " from Collection of size " +
												coll.size() + ", accessed using property path '" + propertyName + "'");
							}
						}
						Iterator<Object> it = iterable.iterator();
						boolean found = false;
						int currIndex = 0;
						for (; it.hasNext(); currIndex++) {
							Object elem = it.next();
							if (currIndex == index) {
								value = elem;
								found = true;
								break;
							}
						}
						if (!found) {
							throw new InvalidPropertyException(getRootClass(), this.nestedPath + propertyName,
									"Cannot get element with index " + index + " from Iterable of size " +

View on GitHub (pinned to e8729d0438)

Solutions

Use a List instead of a Set if positional/indexed access is required.
Check the collection size before attempting indexed access.
Access Set members by iteration rather than by index.

Example fix

// before
public class Doc { private Set<String> tags = new HashSet<>(); ... }
Object t = wrapper.getPropertyValue("tags[1]");

// after
public class Doc { private List<String> tags = new ArrayList<>(); ... }

Defensive patterns

Strategy: validation

Validate before calling

Object coll = wrapper.getPropertyValue(propertyName.replaceAll("\\[.*$", ""));
int idx = Integer.parseInt(propertyName.replaceAll(".*\\[|\\].*", ""));
if (coll instanceof Collection<?> c && idx >= 0 && idx < c.size()) {
    wrapper.getPropertyValue(propertyName);
}

Type guard

static boolean indexInCollection(Collection<?> c, int idx) { return idx >= 0 && idx < c.size(); }

Try / catch

try { Object v = wrapper.getPropertyValue(propertyName); }
catch (InvalidPropertyException ex) { v = null; }

Prevention

Avoid bracket access on Set; use List for positional reads.
Bound-check indices against collection size before indexed access.

When it happens

Trigger: getProperty("set[3]") on a Set of size 2; binding 'tags[10]' onto a Set field; reading an indexed value from a Collection that has fewer elements than the index.

Common situations: Using indexed access (brackets) on a Set; binding positional data to unordered collections; misreading a Set as if it were a List.

Related errors

AI-assisted analysis of spring-projects/spring-framework@e8729d0438 (2026-08-04). Data as JSON: /data/errors/db295b3b51b14fc3.json. Report an issue: GitHub.