Q:

Custom JPA implementation // existing No SQL JPA implementations

Background:
I've been using JPA lately, and I am very impressed by how easily I was able to produce a persistence layer for a reasonably large relational database project. 
We use a lot of no-sql databases at my company, specifically column oriented ones.   I have some questions about potentially using JPA for those databases:
Questions

Can JPA be used with NO-SQL databases?   It stands to reason that if the framework can generate a query for a SQL database and map the results, then it probably could reasonably easily be tailored to generate a different kind of query and a different mapping, for say, querying Hadoop maybe? 
If it's possible, are there any existing implementaitons of JPA that use things besides SQL? 
Are there any good resources on implementing/extending JPA?   I realize TSQL, PLSQL, etc.  must all be specifically addressed in JPA, so there must be an extensibility mechanism we can manipulate. 

A:

As per your question i came across Hibernate OGM which stands for Hibernate Object Grid Mapper which provides JPA (java Persistence api)the support for the NoSQL solutions. 
Hibernate OGM has the following capabilities : - 

persists entities into a NoSQL
datastore specific native queries
full-text queries, using Hibernate Search as indexing engine

I haven't explore more on this framework OGM but looks very promising solution for your questions.  
You can refer to the following URL to get more idea about the Hibernate OGM

http://hibernate.org/ogm/

