jpa/spi/src/main/java/org/jipijapa/event/impl/internal/Notification.java
public static Wrapper startCache(Classification cacheType, Properties properties) throws Exception {
        Wrapper result = null;
        for(EventListener eventListener: eventListeners) {
            Wrapper value = eventListener.startCache(cacheType, properties);
            if (value != null && result == null) {
                result = value;     // return the first non-null wrapper value returned from a listener
            }
        }

        return result;
    }
public static Wrapper startCache(Classification cacheType, Properties properties) throws Exception {
        Wrapper result = null;
        for(EventListener eventListener: eventListeners) {
            Wrapper value = eventListener.startCache(cacheType, properties);
            if (value != null && result == null) {
                result = value;     // return the first non-null wrapper value returned from a listener
            }
        }

        return result;
    }
start cache

@param cacheType
@param properties
@return an opaque cache wrapper that is later passed to stopCache