Most of the time, try to rebuild and reexport the jar.Find out which JAR file contains the problematic Java class. For example, in the case of com.mysql.jdbc.driver, the JAR file that contains it is mysql-connector-java.jar.
Check whether this JAR is present in the application classpath. If not, the JAR should be added to the classpath in Java and the application should be recompiled.
f that JAR is already present in the classpath, make sure the classpath is not overridden (e.g. by a start-up script). After finding out the exact Java classpath used by the application, the JAR file should be added to it.
To fix the Java exception, the mysql-connector JAR should be included in the application classpath.