In the new Oracle Data Integrator 12.2.1 release the Native Format Builder wizard which is used by the Complex File technology is available directly within ODI Studio. Previously users had to use JDeveloper with the SOA Extensions to access it. The Native Format Builder wizard is used to parse a complex file structure and build a Native Schema (nXSD) description out of it, Oracle Data Integrator then uses this nXSD to reverse-engineer, read and write information from complex files.
You can find more information about the Native Format Builder and the Complex File technology in our documentation: http://docs.oracle.com/middleware/1221/odi/develop-connectivity-km/complex_files.htm#ODIKM1397
In addition you can find an Oracle By Example tutorial which will walk you through how to use this feature: https://apexapps.oracle.com/pls/apex/f?p=44785:24:103532390093139:::24:P24_CONTENT_ID,P24_PROD_SECTION_GRP_ID,P24_PREV_PAGE:12572,,24
Finally all the new features introduced in Oracle Data Integrator 12.2.1 are documented in our New Features white paper.