DirectoryResource - Serving Static Content

The DirectoryResource class provides a means to serve static files from within a particular directory in the filesystem. By inspecting the remainder of the path information supplied in an incoming request, instances of DirectoryResource may identify files and serve their contents as a response to such a request.

There are various situations where providing static content is virtually essential:

By instantiating DirectoryResource classes and deploying them in conjunction with MapResource objects (see the "ResourceMap - Simple Mappings from Names to Resources" document), it should be possible to retain control of the serving of static content within a WebStack application. Note, however, that the performance of a system can be improved if the job of serving static content is delegated to a specialised Web server solution - one might, for example, set up an Apache Web server to serve things like stylesheets, script files and images, and then link to the locations of such things in the Web pages generated by the WebStack application.

WebStack API - The DirectoryResource Class

Given a directory from which files shall be served, DirectoryResource uses a simple method to identify files to serve. First, it examines the virtual "path info" and takes the first component of that information. For example, consider the following path information:

/styles.css

Here, DirectoryResource identifies the file to be served as having the name styles.css. Note that any trailing path information would be ignored; for example:

/styles/abc

Here, the file to be served would be identified as having the name styles.

Handling Missing Files

Where no file exists in the specified directory with the identified name, a "file not found" response code is set by the resource and a message is emitted. To modify the simple behaviour of DirectoryResource in this regard, it is recommended that a subclass of DirectoryResource is defined with its own implementation of the not_found method.

Types of Served Files

Given that a file exists in the specified directory, it is usually critical that the file is served along with special file type information so that a user's Web browser may understand the nature of the file's content. For example, a file containing a Web page must be served with a file type indicating that the contents of the file are HTML (or some variant thereof). Instances of DirectoryResource employ a special registry mapping filename extensions to file types in order to automate the process of deciding what type a file might be.

Using the content_types parameter (see below), one might choose to serve all files whose names have the .html extension with the HTML file (or content) type. This would be expressed with the following dictionary:

{"html" : WebStack.Generic.ContentType("text/html", "utf-8")}

Note that the . character is omitted from the filename extension. Where it is tedious to create content type objects and where the same character encoding applies for all types of files, it is possible to use the media_types and default_encoding parameters instead.

Further Reading

The API documentation for the DirectoryResource class provides more information on the usage of the class.

Initialisation

The DirectoryResource class (found in the WebStack.Resources.Static module) accepts the following parameters when being initialised:

directory
The directory from which static files shall be served.
media_types
A dictionary or dictionary-like object mapping filename extensions to media types.
unrecognised_media_type
An optional parameter setting the media type for files whose extensions do not map to any media type according to the media_types parameter.
content_types
A dictionary or dictionary-like object mapping filename extensions to content type objects (such as WebStack.Generic.ContentType).
unrecognised_content_type
An optional parameter setting the content type for files whose extensions do not map to any content type according to the content_types parameter.
default_encoding
An optional parameter setting the character encoding for all media types defined in the media_types and unrecognised_media_type parameters. If not specified, no character encoding will be stated for content associated with such media types.
urlencoding
When specified, this parameter forces a particular interpretation of "URL encoded" character values in the path. Otherwise, the default encoding is employed to interpret such values. (See "URLs and Paths" for an explanation of "URL encoded" values.)

Combining MapResource with DirectoryResource

One might combine MapResource with DirectoryResource to provide stylesheet and script file directories for an application as follows:

from WebStack.Resources.ResourceMap import MapResource
from WebStack.Resources.Static import DirectoryResource

# This is where the application's resources would be obtained.

app_resource = ...

# Here is where we combine MapResource and DirectoryResource.
# Note that one would not necessarily hard-code directory paths into the application.

top_resource = MapResource({
"styles" : DirectoryResource("/usr/share/apps/MyApp/styles", media_types={"css" : "text/css"}),
"scripts" : DirectoryResource("/usr/share/apps/MyApp/scripts", media_types={"js" : "text/javascript"}),
"" : app_resource
})

In the above example, any file in the styles directory whose name ends with .css is served as text/css. Similarly, any file in the scripts directory whose name ends with .js is served as text/javascript.