JBossAop provides an API (appendInterceptor) to add an interceptor at runtime. PojoCache uses this feature extensively to provide user transparency. Every "aspectized" POJO class will have an associated org.jboss.aop.InstanceAdvisor instance. During a putObject(FQN fqn, Object pojo) operation (API explained below), PojoCache will examine to see if there is already a org.jboss.cache.aop.CacheInterceptor attached. (Note that a CacheInterceptor is the entrance of PojoCache to dynamically manage cache contents.) If it has not, one will be added to InstanceAdvisor object. Afterward, any POJO field modification will invoke the corresponding CacheInterceptor instance. Below is a schematic illustration of this process.

JBossAop has the capability to intercept both method level call and field level read write. From the perspective of PojoCache, field level interception is the appropriate mechanism to synchronize with the backend cache store. Please note that,

The figures shown below illustrate operations to perform field read and write. Once a POJO is managed by cache (i.e., after a putObject method has been called), Aop will invoke CacheInterceptor automatically every time there is a field read or write. However, you should see the difference between these figures. While field write operation will go to cache first and, then, invoke the in-memory update, the field read invocation does not involve in-memory reference at all. This is because the value in cache and memory should have been synchronized during write operation. As a result, the field value from the cache is returned.