A separate Oracle WebLogic Server license is required, other than the Oracle WebLogic
Suite for Oracle Applications, utilized for Oracle E-Business Suite Release 12.2. 
The recommended configuration is to have two separate application servers, by installing
the Oracle REST Data Services within Oracle WebLogic Server, on a separate application
server to the one configured for Oracle E-Business Suite. 
Oracle recommends installing a separate application server so that each application
server can be managed independently. 
it is not certified to install Oracle REST Data Services into the Oracle WebLogic Server(s)
utilized by Oracle E-Business Suite Release 12.2. 
Reference: 
http://www.oracle.com/technetwork/developer-tools/apex/learnmore/apex-ebs-extension-white-paper-345780.pdfRead this document: 
http://www.oracle.com/technetwork/developer-tools/apex/learnmore/apex-ebs-extension-white-paper-345780.pdf