[Springframework-developer] Multipart File Handling

[Trevor C. <pr...@se...>]

First some history:
http://sourceforge.net/mailarchive/message.php?msg_id=3891279
http://sourceforge.net/mailarchive/message.php?msg_id=5175276
http://sourceforge.net/mailarchive/forum.php?thread_id=3125561&forum_id=3028
7
http://sourceforge.net/mailarchive/message.php?msg_id=6062288

To address a few things Juergen mentioned previously.

>> a less intrusive way would be to wrap the HttpServletRequest via a filter
I personally don't like the filter approach, at least for the framework.  It
requires additional setup for the user (in the web.xml file) and might be
less understandable since our normal strategy so far has been with resolvers
inside the servlet.

>>we would need to find concrete requirements for this
We have numerous uses for file upload handling.  We have a public photo
contest where users can upload fotos.  We have special access for suppliers
to upload product files (csv) which we then add in to our ordering system.
Finally, we have a web administration interface which allows our client to
upload files to the website so they can be downloaded.  I think that
including this support (multipart handling) is a no-brainer.

Basically, I have used COS exclusively in our projects, but I don't think
that's easy for Spring to use (due to the licensing).  I would simply code
this according to Spring norms using an interface and a default version
using Commons FileUpload.  Later, if somebody wants to create a cos version
we can (but to be honest, if we have a working, integrated solution I'm not
sure that is necessary - at least not in the Spring framework).  Basically,
provide hooks and a default implementation, and allow users to adopt as
necessary.

In our project we had modified the AbstractController and put the code into
it to handle the multipart processing, returning a wrapped
HttpServletRequest through the handlers.  This is very similiar to Juergen's
outline (http://sourceforge.net/mailarchive/message.php?msg_id=3891279).

Since we are migrating to the current Spring codebase, I need to move our
multipart handling code.  The main question is whether we keep it
internally, or place it into Spring.  I propose modifying
org.springframework.web.servlet.DispatcherServlet to have a
"MultipartResolver".  In the DispatcherServlet, the resolver would be called
to wrap the request in doService immediately before getHandler(request) -
currently line 351, and then called to do any cleanup immediately before
exiting the doService method.

I have about 2/3 of the code already written, and I will be writing the rest
between now and Monday.  Does this strategy sound appropriate for Spring
(meaning should I commit it to the Spring codebase) when it's finished?

Trevor D. Cook
Interprise Software