Spring Using Redis @Cacheable

Can any one suggest a Redis (NoSQL DB) example for a Collection type? Generally we use the following (in Spring):

@Cacheable(value = "PRODUCT", key = "#productId" ) 
public Map<String,Object> findProduct(String productId, String productName)
 { return map; } 

which stores the key and value as String, but I need for:

public Map<RestaurantId,Set<Order>>find(String RestaurantId, String productName){ return map; }