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How to obtain connection from EntityManagerFactory? [message #517893]

Tue, 02 March 2010 13:19

Olu

Messages: 29
Registered: October 2009

Junior Member

How do I obtain a connection handler for the underlying connection made by the EntityManagerFactory?

I'm writing an desktop app and need to access the dB. My persistence unit uses an embedded url connection.

Currently I do this by starting JavadB in server mode and get another separate connection on port 1527 as follows:-

// Start JavadB in server mode
 try {
            server = new NetworkServerControl();
            server.start(new PrintWriter(System.out, true));

        } catch (Exception ex) {
            Logger.getLogger(CBTv01View.class.getName()).log(Level.SEVERE, null, ex);
        }

//Get connection to above server

        ClientDataSource ds = new ClientDataSource();
        ds.setPortNumber(1527);
        ds.setDatabaseName(dbName1);
        try {
            conn = ds.getConnection();
        } catch (SQLException ex) {
            Logger.getLogger(CBTv01View.class.getName()).log(Level.SEVERE, null, ex);
        }

The above approach can be useful in development as you can connect to the dB from debug apps etc. However, it seems expensive on resources for deployment and I would like to reuse the connection the EntityManagerFactory has made.

Thanks,

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Re: How to obtain connection from EntityManagerFactory? [message #518046 is a reply to message #517893]

Tue, 02 March 2010 20:47

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

You can get the EclipseLink ServerSession from the factory and get the read or write ConnectionPool from the ServerSession, and then get the currently available connections (DatabaseAccessor) from the pool, and then get the JDBC connections from them.

You can also get the JDBC connection from an EntityManager, if using EclipseLink / JPA 2.0 just call em.unwrap(java.sql.Connection.class).

James : Wiki : Book : Blog : Twitter

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Re: How to obtain connection from EntityManagerFactory? [message #518112 is a reply to message #517893]

Wed, 03 March 2010 06:50

Olu

Messages: 29
Registered: October 2009

Junior Member

Thanks.

This works:-

conn = ((EntityManagerImpl) (entityManager.getDelegate())).getServerSession().getAccessor().getConnection();

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