Retrieving files from the server

GET Method

Preliminaries

This note provides supplementary information about the server's implementation of the standard HTTP GET method to retrieve a resource.

The GET method is the principal protocol for the vast majority of all HTTP requests. It is one of only two methods directly supported via HTML, the other being POST.

GET is the sine qua non of HTTP methods.

A browser generates a GET request when fulfilling HTML declarations similar to these:

<a href="page.html">
<img src="picture.jpg">
<link href="theme.css" type="text/css" rel="stylesheet" >
<script src="interactive.js" type="application/javascript">

When issuing a GET request, the user-agent specifies filtering, sorting, searching, and other limiting criteria in the query-string portion of a URL.

Request/response handlers

The server's request/response cycle for GET requests is handled by a sequence of modules to:

Validate the user's permission to access the resource.
Negotiate acceptance criteria with the user-agent.
Verify that the resource is available.
Dynamically compile certain types of resources.
Compress the resource while in transit.
Prepare the response headers for the return trip.
Send the resource itself in the response body.

This is the sequential order of handlers that fulfill GET requests:

	Request Handler	Optional	Configurable
1	Server Name Indication	no	no
2	Hosts	no	yes
3	IP Access	yes	yes
4	Resource Masks	yes	yes
5	Raw Path	no	no
6	Cookies	no	no
7	Forbidden	yes	yes
8	Cross Origin	yes	yes
9	RBAC	yes	yes
10	User Agent	yes	yes
11	Accept Types	no	yes
12	Accept Language	yes	yes
	Dynamic Handler	Optional	Configurable
13	Router	yes	yes
	Response Handler	Optional	Configurable
14	File Permissions	no	no
15	Content Types	no	yes
16	Etag	yes	no
17	If Modified Since	no	no
18	Last Modified	no	no
19	Cache Control	yes	yes
20	Range	yes	no
21	Content Encoding	yes	yes
22	Content Length	no	no
23	Status Codes	no	yes
24	Push Priority	yes	yes

Success

Successful responses return status code 200 with the bytes of the resource in the response body.

Successful responses have these headers:

content-length even if it is zero.
content-type if the server is properly configured for the filename's extension.
last-modified with the timestamp of the file's modification time.
etag if the etag module is on, with the Etag hash identification for the file.
content-encoding if the encoding module is on, with the compression algorithm applied to the response payload.
content-language if the accept-language module is on, with the language tag associated with the requested resource.
cache-control if the cache-control module is on, containing caching instructions for the browser.
server with the value 'rwserve'.
date with the time when the server began sending the response.

For reference purposes, refer to IETF RFC 7231 Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content section 4.3.1 for the basic protocol expected of HTTP GET requests.