Fix the ClassCastException when CacheRequestBodyFilter is used with CircuitBreakerFilter.

[qnnn]

Currently, the CacheRequestBodyFilter overrides the CACHED_REQUEST_BODY_ATTR attribute with the decoded object. If the fallbackUri of the CircuitBreaker is routed to another route, passing through the AdaptCachedBodyGlobalFilter triggers a ClassCastException(see unit test). The CacheRequestBodyFilter behaves similarly to a ReadBodyRoutePredicateFactory without a predicate. The current modification places the decoded body into CACHE_REQUEST_BODY_OBJECT_KEY to distinguish the responsibilities.

[spencergibb]

I'm afraid, I still don't understand the reason for this change. It is also a breaking change, so this is something that will not happen soon.

[qnnn]

@spencergibb Thank you for your quick reply. This issue arises because the cacheRequestBody replaces the DataBuffer type body in the CACHED_REQUEST_BODY_ATTR attribute with the decoded body. When forwarding, entering the AdaptCachedBodyGlobalFilter again to retrieve the DataBuffer type body throws a ClassCastException. The reproducible route definition is as follows:

.route(
       r -> r.order(-2000).path("/routeTest")
             .filters(f -> f.cacheRequestBody(String.class))
             .uri("forward:/cacheBodyTest"))
.route(
       r -> r.order(-2000).path("/cacheBodyTest")
             .uri("http://127.0.0.1:8888"))

I understand this is a breaking change, and I will follow your arrangements.