[Quickget-develop] my idea for the ftp support task

[steve c. <pre...@ya...>]

Hello team,
After I tracked the code and ran the project, I propose my idea for the =
ftp support.  I hope you can give me comments about it.

class diagram   http://homepage3.seed.net.tw/web@5/stevechang/class.png
sequence diagram for create a new download task  =
http://homepage3.seed.net.tw/web@5/stevechang/seq.png

The design is based on the abstract factory design pattern. =
ProtocolFactory is an abstract factory class that creates =
ProtocolDownloadHelper, Protocol and Command.

Based on the original code, DownloadMap and DownloadRange aren't =
dependent on protocol. So they aren't appear on the class diagram.

In order to seperate the quickget from protocol implementation clearly, =
I use protocol and command interface to wrap the httpclient library and =
ftp implementation is also wrapped under the same interface.

I also find a ftp implementation that has a similar architecture with =
httpclient under apache common net project.

Hope for your comment.

Regards,
Steve