[enhancements] Affects: \

org.springframework.util.PropertyPlaceholderHelper: this is util for replacing the placeholder with environment's value, such as @Value("${aa${cc:defaultv}}"). but the class not support getting all placeholders that I need, i think it should give a chance to return placeholders, in: `
protected String parseStringValue( String value, PlaceholderResolver placeholderResolver, Set visitedPlaceholders)

the items inSet visitedPlaceholders` would be removed by resolved, I think we could add a new method (with a new Set) to finish it.

Comment From: kc910521

ok, i have got the way. i can implements PropertyPlaceholderHelper.PlaceholderResolver, and do caching placeholder names in method #resolvePlaceholder, so that we can reuse the logic of resolver.