ojdbc8.jar has been downloaded from Oracle official web site.
In the project directory, below maven command is ran.
mvn install:install-file -Dfile=<path>/ojdbc8.jar -DgroupId=com.oracle -DartifactId=ojdbc8 -Dversion=12.2.0.1 -Dpackaging=jar
jar file is imported project schema.
Dependency block is added to POM file.
That is all!