So, the real-world example (which as I said, is hopefully a bad one :)
To provide some context (this part is non-hivemind specific) and the objective:
- you have a domain-specific service interface (ContentServiceI in
this case), that you will contribute the caching interceptor to.
- you have a defined a CacheI interface that provides the basic
get/put/remove for a generic object cache (you would like to plug in
things like hashmap/ehcache/swarmcache/your favorite).
- you have an AOP-alliance style interceptor that given a CacheI
implementation, intercepts method calls to your domain-specific
service and makes the appropriate cache get/puts around the method
calls (it's called ContentCacheInterceptor)..
- you wrote the adapter for SwarmCache to implement CacheI.
Ok, that wasn't too bad or unusually mind-boggling :) Now on to the
hivemind-specific tasks:
First, looks like you will need an interceptor factory to explain
hivemind that your ContentCacheInterceptor instances need a CacheI as
a dependency. The class is just a few lines, and extends
MethodInterceptorFactory...
<service-point id="ContentCacheInterceptorFactory"
parameters-occurs="1"
interface="org.apache.hivemind.ServiceInterceptorFactory">
<invoke-factory>
<construct
class="com.freshdirect.cms.cache.ContentCacheInterceptorFactory" />
</invoke-factory>
<parameters-schema>
<element name="cache">
<attribute name="object" required="true"
translator="object"/>
<rules>
<push-attribute attribute="object" />
<invoke-parent method="addElement" />
</rules>
</element>
</parameters-schema>
</service-point>
Ok fine.. Let's bind our configurations to SwarmCache... (Turns out,
the default configuration object in SwarmCache had some warts so you
wrote an adapter for that as well... No big deal, just a small
distraction - but you shall blame that on SwarmCache). Let's define
the schema for it in hivemind...
<schema id="SwarmCacheConfiguration">
<element name="cacheConfiguration">
<attribute name="cacheType" required="true">
<!-- LRU, Auto, Timer, Hybrid -->
</attribute>
<attribute name="multicastIP"/>
<attribute name="lruCacheSize"/>
<attribute name="timerCacheTimeout"/>
<conversion
class="com.freshdirect.cms.cache.SwarmCacheConfiguration"/>
</element>
</schema>
Ok, now you want to have a cache configuration, like so (details about
the symbol source definitions omited for clarity, not everyone needs
that anyway):
<configuration-point id="swarmCacheConfig" schema-id="SwarmCacheConfiguration"/>
<contribution configuration-id="swarmCacheConfig">
<cacheConfiguration multicastIP="${cms.cache.multicastIP}"
cacheType="Hybrid" lruCacheSize="10000"/>
</contribution>
And finally, you'll need a SwarmCache (implements CacheI) instance
using this configuration. Since you have decided that cache
configuration objects should be represented as a configuration in
hivemind, not a service (after all its just a small data carrier, no
biz logic, etc), you'll have to modify the constructor to take a List,
and use the one-and-only element therein. Oops.. well, you're not
gonna backtrack now, stuff needs to get done... :)
<service-point id="StoreCache" interface="com.freshdirect.cms.cache.CacheI">
<invoke-factory>
<construct class="com.freshdirect.cms.cache.SwarmCache">
<string>StoreCache</string>
<configuration>swarmCacheConfig</configuration>
</construct>
</invoke-factory>
</service-point>
Finally (!), you can simply apply a caching interceptor on your
service like this:
<service-point id="StoreContent"
interface="com.freshdirect.cms.application.ContentServiceI">
...
...
<interceptor service-id="ContentCacheInterceptorFactory">
<cache object="service:StoreCache"; />
</interceptor>
</serivce-point>
So, perhaps I'm too lazy or perhaps missed some essential points in
the hivemind docs, but I found this a bit more involved than I
consider reasonable :) It works, no doubt, but was far from a "simple,
consistent, crisp, etc" experience...
regards,
viktor
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