Preload application classes. Uses same strategy as phusion passenger.

railties/lib/initializer.rb

@@ -168,6 +168,9 @@ module Rails
       # Observers are loaded after plugins in case Observers or observed models are modified by plugins.
       load_observers
 
+      # load application classes
+      load_application_classes
+
       # Flag initialized
       Rails.initialized = true
     end
@@ -330,6 +333,14 @@ Run `rake gems:install` to install the missing gems.
       end
     end
 
+    def load_application_classes
+      require_dependency 'application'
+
+      Dir.glob('app/{models,controllers,helpers}/*.rb').each do |file|
+        require_dependency file
+      end
+    end
+
     # For Ruby 1.8, this initialization sets $KCODE to 'u' to enable the
     # multibyte safe operations. Plugin authors supporting other encodings
     # should override this behaviour and set the relevant +default_charset+