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In short, use the wicket.markup.html.form.upload.FileUploadField component in your form (set as multiPart) in order to allow file uploads. Use an implementation of the wicket.markup.html.DynamicWebResource to provide downloads of the content. For a longer description with examples see UploadDownload

What is the difference between setResponsePage(new MyWebPage()) and setResponsePage(MyWebPage.class)

setResponsePage(new MyWebPage()) (or setResponsePage(new MyWebPage(myPageParameters))) can be used if you want to have a bookmarkable url in the browser (your page must have default constructor or PageParameter constructor).
setResponsePage(MyWebPage.class) can be used if you want to pass information to pages on the serverside. This generates a session specific url (most of the time you can use hybrid url coding strategy).

The view layer, markup etc.

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