java.lang.IllegalStateException
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1273)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:316)
        at com.mysql.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:4273)
        at com.mysql.jdbc.ConnectionImpl.close(ConnectionImpl.java:1444)
        at org.hibernate.connection.DriverManagerConnectionProvider.close(DriverManagerConnectionProvider.java:152)
        at org.hibernate.connection.DriverManagerConnectionProvider.finalize(DriverManagerConnectionProvider.java:142)
        at java.lang.ref.Finalizer.invokeFinalizeMethod(Native Method)
        at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:83)
        at java.lang.ref.Finalizer.access$100(Finalizer.java:14)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:160)

Connection con;
try {
   con = ...; // open connection
   // do work
catch (SQLException e) {
   // do whatever
} finally {
    if (con != null && !con.isClosed()) {
        try {
            con.close();
        catch (SQLException e) {
            // Don't throw from here or you'll lose any return/exception from above
            log.error("Failed to close connection", e);
        }
    }
}