Cacheable using field from returned objet as key

[MAndrews]

Hoping this is not a crazy question and that this is the right place to ask it...

I have two @service methods that return the same object out of MongoDB. They have different arguments - and I want to cache the returned object using the object's Id. E.g.,

public User getUserById(String id) { ...

public User getUserByEmailAddress(String emailAddress) { ...

Using @Cacheable I'm abale to easily cache the first one:

@Cacheable(value = "user", key = "#id")
public User getUserById(String id) { ...

I was hoping to use the @CachePut annotation to add caching to the second method - but I'm not sure how to extract the Id from the returned object:

@CachePut(value = "user", key = ???)
public User getUserByEmailAddress(String emailAddress) { ...

Is there a way to do this through SpEL? Or do I need to roll my own Cache/Manager or Aspect as I have done in the past?

Thanks in advance.
M