servlet A receives a request that it forward to servlet B within another web application in the same web container servlet A need to share data with servlet B and data must be not visible to other servlets in A's web application in which object can the data that A shares with B be stored
I feel one option will be to use HttpURLConnection. From the first servlet wecan make a connection to second servlet using this class. Using HttpURLConnection will ensure that the communication is only between two Servlets and helps you two transfer the data without constraints.
As far as I know, JAVA EE specification does't talk about share the data between two web application context. You can't share data either in Request or Response object. You may have reconsider you design.