sealing violation: package oracle.net.ns is sealed
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 JDBCjar file in the CLASSPATH may result in a java.lang.SecurityException:Sealing violation exception.
Solution(Suggested by Oracle) Make sure that the CLASSPATH includesonly 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 wereloaded from two different locations (directories or jar files).
A sealed package is one that essentially says "I know that all classesin this package come from a single jar file. For security reason noother 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.