Handlers

Handlers are functions that have the general signature:

handler(request, response)

It is expected that the handler will use information from the request (e.g. the path) either to populate the response object with the data to send, or to directly write to the output stream via the ResponseWriter instance associated with the request. If a handler writes to the output stream then the server will not attempt additional writes, i.e. the choice to write directly in the handler or not is all-or-nothing.

A number of general-purpose handler functions are provided by default:

Python Handlers

Python handlers are functions which provide a higher-level API over manually updating the response object, by causing the return value of the function to provide (part of) the response. There are three possible sets of values that may be returned:

(status, headers, content)
(headers, content)
content

Here status is either a tuple (status code, message) or simply a integer status code, headers is a list of (field name, value) pairs, and content is a string or an iterable returning strings. Such a function may also update the response manually. For example one may use response.headers.set to set a response header, and only return the content. One may even use this kind of handler, but manipulate the output socket directly, in which case the return value of the function, and the properties of the response object, will be ignored.

The most common way to make a user function into a python handler is to use the provided wptserve.handlers.handler decorator:

from wptserve.handlers import handler

@handler
def test(request, response):
    return [("X-Test": "PASS"), ("Content-Type", "text/plain")], "test"

#Later, assuming we have a Router object called 'router'

router.register("GET", "/test", test)

JSON Handlers

This is a specialisation of the python handler type specifically designed to facilitate providing JSON responses. The API is largely the same as for a normal python handler, but the content part of the return value is JSON encoded, and a default Content-Type header of application/json is added. Again this handler is usually used as a decorator:

from wptserve.handlers import json_handler

@json_handler
def test(request, response):
    return {"test": "PASS"}

Python File Handlers

Python file handlers are designed to provide a vaguely PHP-like interface where each resource corresponds to a particular python file on the filesystem. Typically this is hooked up to a route like ("*", "*.py", python_file_handler), meaning that any .py file will be treated as a handler file (note that this makes python files unsafe in much the same way that .php files are when using PHP).

Unlike PHP, the python files don’t work by outputting text to stdout from the global scope. Instead they must define a single function main with the signature:

main(request, response)

This function then behaves just like those described in Python Handlers above.

asis Handlers

These are used to serve files as literal byte streams including the HTTP status line, headers and body. In the default configuration this handler is invoked for all files with a .asis extension.

File Handlers

File handlers are used to serve static files. By default the content type of these files is set by examining the file extension. However this can be overridden, or additional headers supplied, by providing a file with the same name as the file being served but an additional .headers suffix, i.e. test.html has its headers set from test.html.headers. The format of the .headers file is plaintext, with each line containing:

Header-Name: header_value

In addition headers can be set for a whole directory of files (but not subdirectories), using a file called __dir__.headers.