The Seaside book explains how to write a simple file upload component:

renderContentOn: html
    html form multipart; with: [
        html fileUpload
           callback: [ :file | "self receiveFile: file" ].
        html submitButton: 'Send File' ]

The above code is a good starting point and in many ways showcases Seaside’s elegant approach to callbacks. However for a production site, a major drawback is that the file is loaded into a ByteArray within the image. Even if the file is immediately saved, large files will temporarily consume significant memory. A better solution is to avoid loading the file into your running image altogether and let the front-end server take the strain. In this case I’m using Nginx, which can stream the bytes directly to a file as it is uploaded, avoiding large spikes in consumed memory. An additional benefit is that Nginx allows us to provide the user with customised upload progress feedback.

The associated posts describes how to integrate Seaside and Nginx to create a production-quality file upload solution.

The key features are:

  • The uploaded file is streamed directly to disk by Nginx.
  • The upload occurs in the background, in an AJAX-like style.
  • You should see an upload progress bar update - depending on your uplink speed and the size of the file.
  • You can upload multiple files.

There a quite a few pieces which co-operate to enable this functionality. I’ve described the functionality over four posts:

  • Step 1: Using Nginx upload module to stream file uploads directly to disk.
  • Step 2: Using a hidden iframe to enable ajax-like file uploads.
  • Step 3: Using Nginx upload progress module to report upload progress to the user.
  • Step 4: File upload as a plugable component.

The first three steps describe how the file upload component works. It follows a development journey similar to the one I’ve undertaken in developing the component. Each step adds an additional feature (and complexity). The fourth step describes how to configure a reusable upload component, which I’ve extracted from the component presented in step 3. If you only want to use the component, skip straight to step 4.

The two Nginx components which enable this functionality are:

The default download of Nginx doesn’t include these modules, a previous post - Compiling Nginx to add extra modules describes how to recompile Nginx to include these modules.

Download the code

The code described in the following sections can be downloaded from the repository


People have pointed out Uploadify as an alternative. I can’t see how Uploadify would avoid loading the file directly into memory. It also requires Flash - that said the UI looks very slick and would be worth using for some design clues.


Esteban Lorenzano helped create the initial version of this component.