将java.sql.Connection转换为com.mysql.jdbc.Connection

Question

My database uses MySQL and I'm using hibernate as an ORM framework. I have one instance where I need to access the MySQL Connection object. I use the following code to get a java.sql.Connection object:

getHibernateTemplate().getSessionFactory().getCurrentSession().connection();

However, when I try to cast it to a ( com.mysql.jdbc.Connection ) object, I get the following exception:

java.lang.ClassCastException: $Proxy50 cannot be cast to com.mysql.jdbc.Connection

Strangely, if I do conn.getClass().getName() , the class type returned is '$Proxy50' and not 'java.sql.Connection' or some other meaningful type.

What is the correct method for obtaining a vendor specific Connection object from Hibernate? (I'm trying to read a MySQL system property). Why does my above example not work?

Answer 1

As a rule, you should not need to access the concrete Connection implementation.

But if you really, really need to, here's an explanation: $Proxy40 means it is a JDK dynamic proxy. Spring tends to create these. If yours is created by spring, then, you can get the real object by:

Advised advised = (Advised) connection;
Connection conn = (Connection) advised.getTargetSource().getTarget();

If spring is not involved in the proxying, you should be able to call Connection.unwrap(..) as BalusC suggested (you should be able to to that either way)

Answer 2

What is the correct method for obtaining a vendor specific Connection object from Hibernate?

It depends.

I've unwrapped Proxy's successfully like this. How to unwrap the original object from a dynamic proxy

Kinda scary stuff though, avoid it if you can.

Answer 3

com.mysql.jdbc.Connection implements java.sql.Connection interface. Therefore when you create com.mysql.jdbc.Connection object is also java.sql.Connection object. So you cannot cast operation there because returning object is java.sql.Connection not com.mysql.jdbc.Connection .