In response to Antonio Goncalves' blog post on his wish list for Java EE 7 and particularly on his comments around the inactive JSR-107 JCACHE spec, I'd like to spend a few moments jotting down my thoughts on the subject.
To start with, I am on the JSR-107 expert group, representing Red Hat. I have also been in recent discussions with the JCP about the inactive JSR and what can be done about it.
My feel is JSR-107 needs to be axed. It's been inactive for way too long, it is out of date, and the community is pretty jaded about it. We do, however, need a JSR around distributed caches and in-memory data grids. There is definitely a need in the Java EE 7 umbrella specification, particularly with increasing focus and alignment with cloud. Apps designed to scale would almost certainly need a distributed, in-memory data grid. If Java EE is to be the preferred platform to build Software-as-a-Service offerings, scalability is crucial.
So what should this data grid JSR look like? Well, let's start with JSR-107. After all, I didn't think there was anything wrong with JSR-107, just that it was too limiting/simplistic.
What's in JSR-107?
A quick summary:
- Primary interface - javax.cache.Cache - extending j.u.c.ConcurrentMap
- Adds ability to register, de-register and list event listeners
- Defines a CacheLoader interface for loading/storing cached data
- Defines an evict(K) method, as well as the support for different eviction algorithms
- Defines a ServiceLocator approach to loading the appropriate implementation at runtime
- Defines a CacheManager interface to construct and retrieve Cache instances
Over and above what JSR-107 proposed, I believe the following features are crucial to a useful data grid standard:
- JTA interoperability. The ability to participate in transactions is necessary, both as an XA resource and as a simple cache to front a RDBMS, via JPA
- Define behaviour at certain stages of a tx's lifecycle, particularly with regards to recovery
- Should play nice with JPA's second level cache SPI
- Define and mandate REPLICATION and DISTRIBUTION, as well as SYNCHRONOUS and ASYNCHRONOUS versions of network communications
- An asynchronous, Future-based API (See Infinispan's Async API)
- XML-based config file standardisation (including an XSD)
- Standardise programmatic config bean interfaces