CacheResolver和KeyGenerator有什么区别，何时使用它们中的每一个

Question

I am adding a caching mechanism to my web application. After doing a research I decided to use Ehcache with Spring.

Adding @Cachable annotation to a method will execute the method once and for any further invocations the response will be returned from the cache.

The problem is that I need to decide at runtime (let's suppose according to the logged in user) which cache I want to use.

I have come to a point where I need to decide whether to use KeyGenerators or cacheResolver .

I searched for best practices, when to use each one of them but did not find any good readings. I hope If anybody can clarify the differences and elaborate on best practices and to do's and not to do's.

KeyGenerator:

  @Bean
  public KeyGenerator keyGenerator() {
    return new KeyGenerator() {
      @Override
      public Object generate(Object o, Method method, String loggedInUserId) {
        StringBuilder sb = new StringBuilder();
        sb.append("cache_");
        sb.append(loggedInUserId);
        return sb;
      }
    };

CacheResolver

class loggedInUserCacheResolver implements CacheResolver {
@Override
    public Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context) {
        Collection<Cache> caches = new ArrayList<>();
        // do some logic and return caches to use.
        return caches;
    }
}

Answer 1

The KeyGenerator will only allow you to manipulate the creation of the cache key. However all keys will still belong to a single cache, even though they will not have any collision.

The CacheResolver allow you to use logic to pick which Cache to use.

Given your initial statement, you would need a CacheResolver for your use case. Note that I did not double check if the cache is resolved once or for each invocation.

Note that you could combine both annotations to have a custom cache and a custom key definition.