CommonsMultipartFile を newする方法

File ff = new File("aaa.csv");
String fileName = ff.getName();
MimetypesFileTypeMap map = new MimetypesFileTypeMap();
String contentType = map.getContentType( ff );
DiskFileItemFactory factory = new DiskFileItemFactory();
FileItem fi = factory.createItem( "file", contentType, false, fileName );
InputStream input =  new FileInputStream( ff );
OutputStream output = fi.getOutputStream();
IOUtils.copy( input, output );
IOUtils.closeQuietly( input );
IOUtils.closeQuietly( output );
CommonsMultipartFile cf = new CommonsMultipartFile( fi );

詳しくは、以下参照

http://seakleng.blogspot.jp/2013/12/how-to-create-string.html