This document provides an overview and demonstrations of advanced Apache Cayenne concepts including: 1. Reusing Cayenne and service code between admin apps and discussing object context management. 2. Lifecycle events can be received via callbacks or listeners, with callbacks used for simple initialization and listeners for more complex workflows. 3. Caching in Cayenne includes object caching of entities by ID and query caching of result lists by generated keys, with local caching at the context level and shared caching at the domain level. 4. Demonstrations of object caching, query caching, and turning off cross-context synchronization, using query caching with expiration policies, and considering optimistic locking for performance.

1. Advanced Apache Cayenne
(practical demonstration)
by Andrus Adamchik, ObjectStyle LLC

3. CMS:Admin app
Tapestry stack

4. Admin App
(demo)

5. Admin App - Takeaway
• We can reuse Cayenne and service code between the apps
• When editing objects, ObjectContext is placed in the page scope
and should be reset when we start editing a new object
• Scope in Tapestry is managed with @Persist annotation

6. Lifecycle Events
(demo)

7. Lifecycle Events - Takeway
• Two ways to receive events - callbacks and listeners
• Use callbacks on persistent objects for simple things like
initialization
• Use listeners for more complex workflows, cross-entity
workflows
• Check out DataChannelFilter (will be discussed later)

8. Caching

9. Types of Cache
• What is cached?
• Object cache - objects cached by ID
• Query cache - lists cached by generated cache key

10. Types of Cache
• Where is it cached?
• Local cache - attached to an ObjectContext
• Shared cache - attached to a DataDomain (a common parent
of all ObjectContexts)

11. Object Cache
(very much like EOF)
• Stores objects (or DataRows) by ObjectId
• Prevents unneeded DB trips when navigating object graph
• Ensures uniquing
• Can be auto-synchronized across contexts orVMs
• Memory leak-free (shared - LRU; local - weak refs)

12. Query Cache
(nothing like EOF)
• Stores lists of objects (or lists of DataRows) by query key
• Prevents unneeded DB trips when running queries
• Fully “managed” - time-based or event-based expiration policies
• Lightweight synchronization via cache groups (inVM, cross-VM)
• Scales much better

13. Query Cache
(demo)

14. Caching and Performance

15. Turn off Cross-Context
Synchronization
• Good for desktop apps, terrible for webapps
• unrelated contexts receiving events they don’t care about
• Clustering of object cache doesn’t perform well
• Without clustering, behavior differs for contexts in sameVM vs
differentVM
• Object auto-sync will interfere with optimistic locking

16. Turn off Cross-Context
Synchronization
binder.bindMap(Constants.PROPERTIES_MAP).put(Constants.SERVER_CONTEXTS_SYNC_PROPERTY, "false");

17. Use Query Cache
• Design your app with cache groups in mind
• Implement refresh based on expiration policies
• Implement refresh based on events and CacheInvalidationFilter
• Cluster refresh events. Clustering is lightweight, not prone to
breaking on code version changes

18. Consider Optimistic Locking

19. Caching and Performance
• Don’t try to sync individual objects
• Turn off cross-context synchronization
• Use query cache. Cluster it.
• Use optimistic locking

20. Q&A
Andrus Adamchik
andrus@objectstyle.com
twitter.com/andrus_a