1 files changed, 19 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/static.rb b/actionpack/lib/action_dispatch/middleware/static.rb
index 2764584fe9..25e32cdef8 100644
--- a/actionpack/lib/action_dispatch/middleware/static.rb
+++ b/actionpack/lib/action_dispatch/middleware/static.rb
@@ -2,6 +2,16 @@ require 'rack/utils'
 require 'active_support/core_ext/uri'
 
 module ActionDispatch
+  # This middleware returns a file's contents from disk in the body response.
+  # When initialized it can accept an optional 'Cache-Control' header which
+  # will be set when a response containing a file's contents is delivered.
+  #
+  # This middleware will render the file specified in `env["PATH_INFO"]`
+  # where the base path is in the +root+ directory. For example if the +root+
+  # is set to `public/` then a request with `env["PATH_INFO"]` of
+  # `assets/application.js` will return a response with contents of a file
+  # located at `public/assets/application.js` if the file exists. If the file
+  # does not exist a 404 "File not Found" response will be returned.
   class FileHandler
     def initialize(root, cache_control)
       @root          = root.chomp('/')
@@ -45,6 +55,15 @@ module ActionDispatch
     end
   end
 
+  # This middleware will attempt to return the contents of a file's body from
+  # disk in the response.  If a file is not found on disk, the request will be
+  # delegated to the application stack. This middleware is commonly initialized
+  # to serve assets from a server's `public/` directory.
+  #
+  # This middleware verifies the path to ensure that only files
+  # living in the root directory can be rendered. A request cannot
+  # produce a directory traversal using this middleware. Only 'GET' and 'HEAD'
+  # requests will result in a file being returned.
   class Static
     def initialize(app, path, cache_control=nil)
       @app = app