Is it possible to define more KeyGenerator classes for cache in Spring version 3.1.x?

Question

I have a configuration class which implements CachingConfigurer to define a cache manager with a specific key generator, but I should use different key generators per caches.

There is an option form Spring 4.1 to specify a key generator per operation:

@Cacheable(cacheNames="cacheName1", keyGenerator="myKeyGenerator1") 
@Cacheable(cacheNames="cacheName2", keyGenerator="myKeyGenerator2") 

I'm wondering if there is any alternative for this in Spring 3.1?

Answer 1

Yes, there is an alternative. The KeyGenerator gives you access to the Method being invoked so you could create a composite of your own kind and redirect accordingly. Here's a pseudo code that would do that:

@MyKeyGenerator("myKeyGenerator1")
@Cacheable(cacheNames="cacheName1")
Foo method1(...) { ... }

@MyKeyGenerator("myKeyGenerator2")
@Cacheable(cacheNames="cacheName2")
Bar method2(...) { ... }

MyKeyGenerator is an annotation of yours. Then you can create a single keyGenerator that looks like this:

public class MyKeyGenerator extends DefaultKeyGenerator {

    @Override
    public Object generate(Object target, Method method, 
            Object... params) {

        MyKeyGenerator myKeyGenerator = 
            method.getAnnotation(MyKeyGenerator.class);
        if (myKeyGenerator != null) {
            // read your annotation and invoke the proper
            // key generator according to the value
        } else {
            super.generate(target, method, params);
        }
    }
}

You can use CachingConfigurer to specify MyKeyGenerator instead of the default.

Note: an update to Spring Framework 4 is probably in order anyway and you'd benefit from tons of other nice features. Just saying.