Try this if the above doesn't work..........
In Server perspective, under 'Server Configuration' window at the bottom, double click on the server you are using. In the properties window at right side, click on Environment tab (3rd tab), and under 'ws.ext.dirs' click on 'Add External Jars', select .jar from local disk, then save the server and restart it.
If the above optios doesn't work, use below 2 options:
1. Go to Window -> Preferences -> Java -> Classpath Variables -> NEW button -> Give Name/path -> OK
For
JDBC drivers:
2. Go to Window -> Preferences -> JDBC Drivers -> Add Jar -> OK