http_path.pl -- Abstract specification of HTTP server locations
This module provides an abstract specification of HTTP server locations that is inspired on absolute_file_name/3. The specification is done by adding rules to the dynamic multifile predicate http:location/3. The speficiation is very similar to file_search_path/2, but takes an additional argument with options. Currently only one option is defined:
- If two rules match, take the one with highest priority. Using
priorities is needed because we want to be able to overrule
paths, but we do not want to become dependent on clause ordering.
The default priority is 0. Note however that notably libraries may decide to provide a fall-back using a negative priority. We suggest -100 for such cases.
This library predefines a single location at priority -100:
- The root of the server. Default is /, but this may be overruled
using the setting (see setting/2)
Here is an example that binds
/login to login/1. The user can reuse
this application while moving all locations using a new rule for the
admin location with the option
:- multifile http:location/3. :- dynamic http:location/3. http:location(admin, /, ). :- http_handler(admin(login), login, ). login(Request) :- ...
- http:location(+Alias, -Expansion, -Options) is nondet[multifile]
- Multifile hook used to specify new HTTP locations. Alias is the
name of the abstract path. Expansion is either a term
Alias2(Relative), telling http_absolute_location/3 to translate
Alias by first translating Alias2 and then applying the relative
path Relative or, Expansion is an absolute location, i.e., one
that starts with a
/. Options currently only supports the priority of the path. If http:location/3 returns multiple solutions the one with the highest priority is selected. The default priority is 0.
This library provides a default for the abstract location
root. This defaults to the setting http:prefix or, when not available to the path
/. It is adviced to define all locations (ultimately) relative to
root. For example, use
- http_absolute_uri(+Spec, -URI) is det
- URI is the absolute (i.e., starting with
http://) URI for the abstract specification Spec. Use http_absolute_location/3 to create references to locations on the same server.
- http_absolute_location(+Spec, -Path, +Options) is det
- Path is the HTTP location for the abstract specification Spec.
- Path is made relative to Base. Default is to generate absolute URLs.
- HTTP locations resolved through http_absolute_location/3 are cached. This predicate wipes the cache. The cache is automatically wiped by make/0 and if the setting http:prefix is changed.