Java rest webservice architechture to handle login database and customer database for mysql

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Java

MySQL

REST

I have constructing architect for Rest webservice in Java with MySQL+JPA+Hibernate using token based authentication system with Login and Customer database separate. I need help on below,

My workflow is, User authenticate by username and password and system generate Authentication Token. By using this token user can perform further operations. Token will be generated from Login Database. and using same login token user can send request to client database.
I am able to make database connection to my login database successfully using persistent.xml. But I have problem my making connection with dynamic connection with my client database on each request.

Please suggest me Rest webservice architechture to handle Login Database and Customer Database in Java Rest webservice.

What I have tried:

I have used DBContext in .net but I do not have any idea in Java