The contract for StringValueResolver.resolveStringValue should be more explicit [SPR-14842]

[spring-projects-issues]

Ryan Baxter opened SPR-14842 and commented

The contract is unclear as to what value should be returned if the resolver could not resolve the value. Should it return null? Should it return the original value?

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Affects: 4.3.3

Reference URL: https://github.com/spring-projects/spring-framework/blob/master/spring-core/src/main/java/org/springframework/util/StringValueResolver.java#L37

Referenced from: commits 20419d7, fe19cfd

[spring-projects-issues]

Juergen Hoeller commented

I've tightened the javadoc a bit to indicate that

• the original String value will never be null
• the resolved String may be null (when resolved to a null value)
• the resolved String may be the original String value itself (in case of no placeholders to resolve or when ignoring unresolvable placeholders)
• an IllegalArgumentException is to be thrown when rejecting an unresolvable value

So certainly don't return null for unresolvable (since null is treated as a regular value), and only return the original String if you'd like to leniently ignore unresolvable values (which is configurable in e.g. our placeholder configurers).