JDBC Drivers / data source problems for Jdeveloper 11.1.2.

When you upgrade to Jdeveloper 11.1.2.x you might face multiple problems when you are using jdbc data sources as you configured with the 11.1.1.x versions.
You might face problems like this

Caused by: java.lang.AbstractMethodError: com.ibm.as400.access.AS400JDBCConnection.isWrapperFor(Ljava/lang/Class;)Z
    at weblogic.jdbc.wrapper.JDBCWrapperImpl.isWrapperFor(JDBCWrapperImpl.java:202)



Solution:
Weblogic 11.1.2 supports JDBC4.0 by default. So All JDBC drivers should be
JDBC 4.0 compatible.

more about JDBC 4.0 refer http://today.java.net/pub/a/today/2007/04/10/whats-new-in-jdbc-40.html

JDBC 4.0 Drivers
SQL Server : Download  JDBC 4.0  driver from http://www.microsoft.com/en-us/download/details.aspx?id=11774  and use sqljdbc4.jar in your classpath
JTOpen / JT400:  Download JDBC 4.0 driver from http://sourceforge.net/projects/jt400/files/JTOpen-full/7.8/jtopen_7_8_jdbc40_jdk6.zip/download

jars in Domain/lib not Pickedup
Weblogic 11.1.2 doesn’t automatically pick up jars from the the domain lib directory. To fix this, you have to set the class path in the weblogic start command. this can be done in many ways. One way is to edit bin/startWebLogic.cmd and add a line set
CLASSPATH=%SAVE_CLASSPATH%;path to your driver;