From this documentation at Oracle : Known Issues and Limitations :
java.lang.SecurityException: Sealing violation exception (ID 6554602)
Description
Starting with JDBC 10.2 drivers, having more than one JDBC
jar file in the CLASSPATH may result in a java.lang.SecurityException:
Sealing violation exception.
Solution
(Suggested by Oracle) Make sure that the CLASSPATH includes
only one JDBC driver JAR file.
And this forum : SecurityException: sealing violation from Class.forName
A sealing violation means that some classes from a sealed package were
loaded from two different locations (directories or jar files).
A sealed package is one that essentially says "I know that all classes
in this package come from a single jar file. For security reason no
other location may provide classes that are in this package".
Chances are you have two Oracle JDBC driver jars in your classpath.
So make sure that you don't have multiple Oracle JDBC driver jar libraries in your classpath.