Question

When should I reuse a cache in Ehcache and when should I create a new one?

Example 1:

I have the following methods:

public Dog getBestDog(String name) {
    //Find the best dog with the provided name
}

public Dog getBestBrownDog(String name) {
    //Find the best brown dog with the provided name
}

For a given String (e.g. “rover”), these two methods could return a different Dog object.

Should I annotate them both with @Cacheable(cacheName = "dogs") or should I put them in two different caches, “bestDogs” and “bestBrownDogs”?

Example 2:

I have the following methods:

public Dog getBestDogByName(String name) {
    //Find the best dog with the provided name
}

public Dog getBestDogByColour(String colour) {
    //Find the best dog with the provided colour
}

Name “rover” and colour “doggy-colour” could return the same Dog.

Should I annotate them both with @Cacheable(cacheName = "dogs") or should I put them in two different caches, ‘dogsByName’ and ‘dogsByColour’?

Answer 1

Whenever you have a scenario where the same key can result in different results, then you probably want a separate cache.

Example 1:

getBestDog(name) – use the name as the key from ‘best-dogs’ cache

getBestBrownDog(name) – use the name as the key from ‘best-brown-dogs’ cache

Example 2:

getBestDogByName(name) – same as example 1, use name as key from ‘best-dogs’ cache

getBestDogByColour(colour) – use colour as key from ‘best-dogs-by-colour’ cache

Which leaves you with 3 caches, ‘best-dogs’, ‘best-brown-dogs’, ‘best-dogs-by-colour’

In theory, you could merge ‘best-dogs’ and ‘best-dogs-by-colour’… but maybe you have a dog who is called ‘red’.. so that would be an unaccounted for edge case.