[ http://issues.apache.org/jira/browse/OPENJPA-24?page=comments#action_12432705 ] Pinaki Poddar commented on OPENJPA-24: --------------------------------------
One use case for extension of OpenJPA implementations is backward compatibility of Kodo 4.1 with Kodo 4.0. In Kodo 4.0, we have published interfaces such as kodo.persistence.KodoEntityManagerFactory/KodoEntityManager. The applications compiled with Kodo 4.0 API to work with Kodo 4.1 runtime (based on OpenJPA), we would be supporting KodoEntityManagerFactory and other published interfaces. The published Kodo 4.0 interfaces would be redefined to extend openjpa interfaces for Kodo 4.1. I'm working on some related code for backwards-compatibility of Kodo, which turns out to be a similar problem to extensibility of OpenJPA. Let's compare notes, and see where we're overlapping and how we can help each other out. > Allow OpenJPA to be extensible > ------------------------------ > > Key: OPENJPA-24 > URL: http://issues.apache.org/jira/browse/OPENJPA-24 > Project: OpenJPA > Issue Type: Bug > Components: kernel > Reporter: Kevin Sutter > Assigned To: Kevin Sutter > > The current OpenJPA architecture is not extendable to other implementations. > For example, if somebody wanted to provide their own PersistenceProvider > implementation, simply extending the > org.apache.openjpa.PersistenceProviderImpl would not suffice due to the > dependencies in the ConfigurationProviderImpl. The discussion for this > improvement was started on the dev mailing list. Once it was determined that > there was more to this request than a simple conditional or two, we decided > to open a JIRA report. > The complete history of this request can be found in the OpenJPA dev mailing > list. The first message was posted by me (Kevin Sutter) on August 14, titled > "Extending the OpenJPA Implementation". I will attempt to paraphrase the > current state of the problem... > We have three main players in this issue. The PersistenceProvider, the > ConfigurationProvider, and the ProductDerivation (along with the various > implementations of these interfaces). Currently, the ConfigurationProvider > is in the lib and is unaware of any specific persistence requirements. The > ProductDerivation is in the kernel and, unfortunately, is aware of > persistence requirements, specifically the spec and store types. Abe's > postings have indicated that we need to make these two interfaces more aware > of each other and work with each other. We need to start with either making > ConfigurationProvider more persistence-aware and move it into kernel, or make > ProductDerivations less persistence-aware and move it into lib. The latter > approach is preferred. > After we get this re-organization of the base framework complete, we still > have a couple of other issues ot resolve: > * Still need the ability to extend EMF's through a ProductDerivation. > This should be doable by adding a new PluginValue to indicate what class of > EMF to load. > * There is still a question as to whether we will need to provide a > custom PersistenceProviderImpl and ConfigurationProviderImpl pair. I still > think this will be necessary. And, one of Abe's posts indicated that this > might help with class loading issues when multiple versions of OpenJPA-based > implementations are available in the same system. > I also posted these questions last Friday. (Abe has responded with some > answers, but I wanted to get this JIRA report created before trying to > paraphrase his answers.) > * You mention in several places about separating away the notion of > specs and stores. In a general sense, I understand what these are. But, can > you elaborate on how these types are used in the ConfigurationProvider and > ProductDerivation interfaces? > * I've moved the ProductDerivation interface to the lib and added the > "load" methods from the ConfigurationProvider (as described in your previous > notes). And, I've started to clean up the implementations that depend on > these interfaces. But, concerning the implementation of the load methods... > Now that we need to return a ConfigurationProvider, would you expect that we > just new up a ConfigurationProviderImpl and then just call across to the > "load" methods on the implementation? Since we want to keep the > ProductDerivations stateless, I'm not sure how else you were expecting to > create a ConfigurationProvider to return on these "load" methods. > * Now that ConfigurationProvider is bare, the > ConfigurationTestConfigurationProvider doesn't have much function. I'll need > to take a look to see if this is even required any longer. > * Can you shed a bit more light on the Configurations class? It doesn't > implement nor extend any interfaces or classes, but it seems to provide many > of the same methods as ConfigurationProvider, but as statics. And, it's > dependent on having a Provider. Can you explain the relationship of this > class in the bigger picture and how you think it might be affected by thes > changes? > That's enough for the initial JIRA report. We will now track this problem > here instead of the dev mailing list. Thanks. > Kevin -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
