`DataBinder` throws `StringIndexOutOfBoundsException` for indexed property without nested property path

[ecolinet-orange]

Trying to migrate from Spring Famework 6.1 to 6.2, I get an exception in Spring's validation code, located in the DataBinder::getIndexes method.

When I look at the code it looks like a bug.

@Nullable
private static SortedSet<Integer> getIndexes(String paramPath, ValueResolver valueResolver) {
	SortedSet<Integer> indexes = null;
	for (String name : valueResolver.getNames()) {
		if (name.startsWith(paramPath + "[")) {
			int endIndex = name.indexOf(']', paramPath.length() + 2);		// returns -1
			String rawIndex = name.substring(paramPath.length() + 1, endIndex); 	// throws java.lang.StringIndexOutOfBoundsException
			int index = Integer.parseInt(rawIndex);
			indexes = (indexes != null ? indexes : new TreeSet<>());
			indexes.add(index);
		}
	}
	return indexes;
}

In my case, name contains someField[], so paramPath.length() + 2 points outside the string. I think that paramPath.length() + 1 should be used instead.

[sbrannen]

This is closely related to:

• DataBinder throws StringIndexOutOfBoundsException for map property without nested property path #34043

And the two should be looked at in conjunction.

[simonbasle]

@ecolinet-orange can you provide a more detailed example of something that was working in 6.1.x? Even though I'm able to reproduce the exception when posting an array or list, the case I have simply leads to a null value for the bound param on 6.1.x...

[simonbasle]

@ecolinet-orange I have attempted a fix, but please still ping me in a comment to provide the requested details, and I'll reopen this issue if needed. Feel free to also test out snapshots and report if your issue is indeed fixed.