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Re: Policy to wrap route with a cache


Hi Balazs,

good work. I was thinking of doing such thing myself. It think the Policy interface is the way to go, since it wraps all the processors.

How about Endpoints (consumers/producers)? Would processor policies work for them as well?

The code looks pretty complicated though. Could you elaborate a bit on the AsyncCallback part?

Regards,
Ralf


On 06/28/2018 02:03 AM, Balazs Szeti wrote:
Hi Camel Users,

In Spring we have the @Cacheable
<https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-caching.html>
annotation that provides an easy way to wrap a method call with a cache.
The method result is cached and the method is not executed the next time
the it's called with the same input parameters.

I was wondering if we have something similar for Camel routes, where we can
cache the "result" of a route and execute the next time only if nothing is
found in the cache.

I haven't found any solution out-of-the-box, but a few blogs
<https://medium.com/@joelicious/camel-3scale-component-part-2-355faaaba5e0>
about doing similar caching in certain specific scenarios using the Policy
for processors. So I tried to put together a more generic solution:
See CachePolicy class:
https://gist.github.com/bszeti/552bf7a1f05a75fc2964a4ce7ce889b5

This is how it can be used in a route:
https://gist.github.com/bszeti/4f855cd80cd69e3953ff990b0ae056a2

public class CachedRoute extends RouteBuilder{
     @Override
     public void configure() throws Exception {
       from("direct:cachedRoute")
         *.policy(getUserDataCachePolicy())*

.setProperty("userData").method(userDataService.class,"lookupUserDataByName");
     }

     //Cache user data by user name. If user data is found in cache the rest
of the route is not executed.
     *private Policy getUserDataCachePolicy()*{
         CachePolicy cachePolicy = new CachePolicy();
         cachePolicy.setCache(cacheManager.getCache("userDataCache"));

         //User name is the cache key
         cachePolicy.setKeyExpression(simple("${header.userName}"));

         //What to do with the cached object if found
         cachePolicy.setApplyCachedObject(new BiConsumer<Exchange, Object>()
{
             public void accept(Exchange exchange, Object cached){
                 exchange.setProperty("userData",cached);
             }
         });

         //Cache userData at the end of the route
         cachePolicy.setValueExpression(exchangeProperty("userData"));

         return cachePolicy;
     }


It would be great to know if someone tried anything similar and especially
if the "AsyncCallback()" looks OK in CachePolicy.wrap(). I found that piece
always a bit tricky...

Thanks,
Balazs