Spring cache applying caching on a generic method by dynamically getting the cachname based on the return type

Question

The method getById is located in an Abstract class named AbstractCachedResult.

public abstract class AbstractCachedResult<T extends BaseResource> {

    @Cacheable(value = "dynamicName")
    public T getById(String id){
      //program logic
    }
}

Many other service classes will be inheriting from this class. For ex :

public class UserService extends AbstractCachedResult<User> {
    
    //program logic
}

Since I am setting the @Cacheable(value = "dynamicName") in the abstract class I wouldn't be able to know the type of the class that was returned by the method. I need to be able to get the name of the class dynamically so that for each method invocation from its inherited class the correct cache is used.

I have came across another post. Here they are passing the entity class name as a parameter which I cannot do. I need to get the type of the returned data dynamically so that I could us the @Caching annotation which is the #2 soluton. Is there a way to do this?

Answer 1

Arguably, the simplest and most obvious solution, especially for maintainers, would be to override the getById(:String) method in the subclass, like so:

public class UserService extends AbstractCachedResult<User> {

    @Cacheable("UserCache")
    public User getById(String id) {
        super.id(id);
    }

    // additional logic
}

Alternatively, you might be able to implement a "custom" CacheResolver (see doc and Javadoc) that is able to inspect the class generic signature of the (target) subclass.

Finally, under-the-hood, Spring's Cache Abstraction is implemented with Spring AOP. For real, low-level control, it should be possible to write custom AOP Interceptor not unlike Spring's default CacheInterceptor (Javadoc). Your own AOP Advice could even be ordered relative to the Cacheable Advice, if needed.

Honestly, I think the first option I presented above is the best approach. Not every service class may need to cache the result of the getById(:String) operation. Caching really depends on the transactional nature of the data and how frequently the data changes.

Use your best judgement.