Interesting question regarding building interfaces to legacy systems

Here is a very interesting question regarding building of interfaces to legacy systems; http://qr.ae/8Q3PT

What are the best ways to construct interfaces to legacy FTP systems to and from an Enterprise Java EE Websphere transactional application? 
The legacy systems only have FTP interfaces, and FTP is the only means of transferring data to and from those applications, the files are column positioned flat files and not in XML format. The FTP part of the interface is set and is not going to be changed for the foreseeable future. What are the best solutions for performing extracts of the input files, cleansing the data applying any required transforming and loading into the Enterprise application’s transactional database? Is the concept ETL in terms of BI systems applicable in this type of domain? What technologies are out there to do this? Can it be done in Java / is that advisable, are there better ways to do this than in Oracle Stored Procedures with staging tables? What mechanisms / patterns perform well and are scalable?