How to integrate multiple database?

We have two categories of user. one category is the employee of company, which located in the original database of Openfire (MySQL), the other is our website user category, which located in an other Oracle database. We plan to integrate those two categories users into Openfire. And even, maybe integrate more databases in the future.

According to the db-integration-guide, there has no solution to meet our requirement, because there only has ONE database can be used at one time.

I have two ideas about this:

  1. Use Openfire Clustering. But i don’t know whether it can work well and resolve our problem.

  2. Develop a plugin to integrate multiple databases. But it will take a long time and has much risk.

Would somebody tell me how to get the resolution, whick has more concision and more expansibility.