Question

I have an application using Spring MVC and Spring Security.

The application project has ejbs and web application.

I have a common database for users and one database by users’ group.

So, when a user authenticate, Spring Security use the common database to check login/password and when a controller calls an ejb, the entity manager connects to the user’s group database.

My goal is : create users/groups and their associated database on the fly.

Example :

The common database localhost:3306 database_schema1 contains

  USERS
----------------------
| NAME    | GROUP_ID |
----------------------
| Pierre  |        1 |
| Paul    |        1 |
| Jacques |        2 |
----------------------

  GROUPS
------------------------------------------
| ID | URL            | SCHEMA_NAME      |
------------------------------------------
|  1 | localhost:3307 | database_schema1 |
|  2 | localhost:3308 | database_schema1 |
------------------------------------------

When Pierre authenticate, the home page call an ejb. This ejb has an entity manager which has to connects to group 1 database localhost:3307 with schema database_schema1

If Jacques authenticate, it must be group 2 database.

How can I do to tell to the entity manager to use a given database that I don’t know when I build the project?

I mean, I don’t want to use persistence.xml in my ejb but dynamically initialize entity manager depending on the user authenticated.

Does Persistence.createEntityManagerFactory() will work in this context ? And if it does, is it the best solution?

Answer 1

You can do this by removing the database URL from persistence.xml and specifying it at runtime:

Map<String, String> params = new HashMap<String, String>();
// put the correct URL here
// you can also specify any other parameter from 'persistence.xml'
String dbUrl = "jdbc:mysql://localhost:3308/database_schema1"; 
params.put("javax.persistence.jdbc.url", dbUrl);
EntityManagerFactory factory = 
  Persistence.createEntityManagerFactory("...", params);

Then, use this factory object to create EntityManager instances as needed.