What strategies exist for using Spring Cache on methods that take an array or collection parameter?

Solution 1:

Spring's Cache Abstraction does not support this behavior out-of-the-box. However, it does not mean it is not possible; it's just a bit more work to support the desired behavior.

I wrote a small example demonstrating how a developer might accomplish this. The example uses Spring's ConcurrentMapCacheManager to demonstrate the customizations. This example will need to be adapted to your desired caching provider (e.g. Hazelcast, Coherence, etc).

In short, you need to override the CacheManager implementation's method for "decorating" the Cache. This varies from implementation to implementation. In the ConcurrentMapCacheManager, the method is createConcurrentMapCache(name:String). In Spring Data GemFire, you would override the getCache(name:String) method to decorate the Cache returned. For Guava, it would be the createGuavaCache(name:String) in the GuavaCacheManager, and so on.

Then your custom, decorated Cache implementation (perhaps/ideally, delegating to the actual Cache impl, from this) would handle caching Collections of keys and corresponding values.

There are few limitations of this approach:

1. A cache miss is all or nothing; i.e. partial keys cached will be considered a miss if any single key is missing. Spring (OOTB) does not let you simultaneously return cache values and call the method for the diff. That would require some very extensive modifications to the Cache Abstraction that I would not recommend.

2. My implementation is just an example so I chose not to implement the Cache.putIfAbsent(key, value) operation (here).

3. While my implementation works, it could be made more robust.

Anyway, I hope it provides some insight in how to handle this situation properly.

The test class is self-contained (uses Spring JavaConfig) and can run without any extra dependencies (beyond Spring, JUnit and the JRE).

Cheers!