File upload with Snap

File upload is a very basic HTTP operation handled through Content-type: multipart/form-data. In this recipe, we will create an HTML form and upload a file through it. While the file is being uploaded, we will dynamically process the contents, and report the summary.

How to do it...

1. Create a new project, file-upload, with a simple stack template:

        stack new file-upload simple

2. Add a dependency on the snap-core library in the build-depends subsection of the executable section, as follows:

  executable file-upload
    hs-source-dirs:      src
    main-is:             Main.hs
    default-language:    Haskell2010
    build-depends:       base >= 4.7 && < 5
                       , snap-core
                       , snap-server
                       , heist
                       , snap
                       , lens
                       , bytestring
                       , io-streams
                       , text

3. Use the following command to solve the constraints...