The OKAPI Project
:: Opencaching API Reference
OKAPI is a publically available
API
for "National Opencaching" sites.
- It provides OC site with a set of useful well-documented API methods,
- Allows external developers to easily read public Opencaching data,
- Allows read and write private (user-related) data with OAuth Authentication.
The project has grown to become a standard and common API for all National
Opencaching.xx sites. This OKAPI installation provides services for the
https://opencache.uk/ site.
Here is the list of other OKAPI installations:
Other links you might want to check out:
* Opencaching.DE includes other sites - Opencaching.IT and Opencaching.FR
- which are in fact the one site visible on multiple domains.
All three share one database, so you can access all their data through
Opencaching.DE OKAPI installation.
How can I use OKAPI?
We assume that you're a software developer and you know the basics.
OKAPI is a set of simple web services. Basicly, you make a proper HTTP
request, and you receive a JSON-formatted response, that you may parse and use
within your application.
Example. Click the following link to run a method that prints out the
list of all available methods:
You've just made your first OKAPI request! This method was a simple one
though. It didn't require any arguments and it didn't require you to use a
Consumer Key. Other methods are more complex and require you to use
your own API key.
Authentication Levels
Each OKAPI method has a minimum authentication level.
"Minimum" means that if you want to call a method which requires "Level 1"
authentication, you have to use "Level 1" authentication or higher
("Level 2" or "Level 3" will also work).
Most methods can be called with "Level 1" authentication, so for most
applications you won't have learn OAuth.
-
Level 0. Anonymous. You may call such methods with no extra
authentication-related arguments.
some_method?arg=44
-
Level 1. Simple Consumer Authentication. You must call this
method with consumer_key argument and provide the key which has
been generated for your application on the
Sign up page.
some_method?arg=44&consumer_key=a7Lkeqf8CjNQTL522dH8
-
Level 2. OAuth Consumer Signature. You must call this method
with proper OAuth Consumer signature (based on your Consumer Secret).
For most languages there are some OAuth 1.0a libraries which can
do this for you.
some_method
?arg=44
&oauth_consumer_key=a7Lkeqf8CjNQTL522dH8
&oauth_nonce=1987981
&oauth_signature_method=HMAC-SHA1
&oauth_timestamp=1313882320
&oauth_version=1.0
&oauth_signature=mWEpK2e%2fm8QYZk1BMm%2fRR74B3Co%3d
-
Level 3. OAuth Consumer+Token Signature. You must call this
method with proper OAuth Consumer+Token signature (based on both
Consumer Secret and Token Secret). For most languages there are some
OAuth 1.0a libraries which can do this for you.
some_method
?arg=44
&oauth_consumer_key=a7Lkeqf8CjNQTL522dH8
&oauth_nonce=2993717
&oauth_signature_method=HMAC-SHA1
&oauth_timestamp=1313882596
&oauth_token=AKQbwa28Afp1YvQAqSyK
&oauth_version=1.0
&oauth_signature=qbNiWkUS93fz6ADoNcjuJ7psB%2bQ%3d
GET or POST?
Whichever you want. OKAPI will treat GET and POST requests equally. You may
also use the HTTP Authorization header for passing OAuth
arguments. OKAPI does not support other HTTP request types (such as PUT or
DELETE).
A warning about HTML fields
Many of the fields returned in OKAPI responses are formatted in HTML.
However, most of these fields come directly from the underlying Opencaching
database. Currently, these fields are not validated by OKAPI. They
should be validated by the Opencaching site itself (prior to inserting
it to the database), but we cannot guarantee that they will be. And you
shouldn't count on it too.
You must assume that our HTML content may contain anything, including
invalid HTML markup, tracking images (pixels), or even
XSS vectors.
This also applies to the descriptions included in the GPX files.
Most of the methods return simple objects, such as lists and dictionaries of
strings and integers. We may format such objects for you in several ways. If
you want to change the default (JSON) then you should include common
formatting parameters in your request:
Some methods expose formatting of their own, for example, they may return a
JPEG or GPX file. Such methods do not accept common formatting
parameters.
Important: Almost all of the returned data types are
extendible. This means, that (in future) they may contain data that
currently they don't. Such data will be included in backward-compatible
manner, but still you should remember about it in some cases (i.e. when
iterating over attributes of an object). This additional data may appear as
extra elements in GPX files or extra keys in JSON responses. Your software
must ignore such occurrences if it doesn't understand them!
OAuth Dance URLs
If you want to use Level 3 methods, you will first have to perform
"the OAuth dance" (series of method calls and redirects which provide you with
an Access Token).
The three OAuth request URLs defined in the
OAuth specification are:
Things you should pay attention to:
-
The oauth_callback argument of the request_token
method is required.
As the OAuth 1.0a specification states, it should be set to
"oob" or a callback URL (this usually starts with https://, but
you can use any other scheme, e.g. myapp://).
For most OAuth client libraries, you just should provide
"https://opencache.uk/okapi/services/oauth/request_token?oauth_callback=oob"
as the request_token URL, to get it started. Later on, you'll probably
want to replace "oob" with something more useful (your own callback).
-
The oauth_verifier argument of the access_token method
is also required.
When user authorizes your application, he will receive a PIN code
(OAuth verifier). You have to use this code to receive your Access
Token.
-
Access Tokens do not expire (but can be revoked). This means,
that once the user authorizes your application, you receive a "lifetime
access" to his/her account. The user may still revoke access to
his account from your application - when this happens, you will have to
redo the authorization dance.
Advanced error handling
Basic rules apply:
- If all goes well, OKAPI will respond with a HTTP 200 status.
- If there is something wrong with your request, you will get a HTTP
4xx response. The body will contain a JSON object describing the error
(see below). These kind of responses should trigger some kind of an
exception inside your application.
- If something goes wrong on our part, you will get a HTTP
5xx response. Usually you should treat such errors as other I/O errors
(e.g. display a "No connection, try later" notice). We will try to fix such
errors as soon as possible.
- Sometimes, due to invalid server configuration, you may receive HTTP
200 instead of HTTP 500. We know that's "unprofessional", but we
cannot guarantee that all OC servers are configured properly
(example).
If you get HTTP 200 and you cannot parse the server response,
you should treat it as HTTP 500.
Every HTTP 4xx error will contain an additional description in the
response body. This description will be always formatted in JSON
(regardless of the format parameter you might have used in your
request). You can use this information to pinpoint the source of the error.
The error response is a dictionary with a single error key. Its value
contains at least the following keys:
- developer_message - description of the error,
-
reason_stack - a list of keywords which depicts the exception's
position in our exception class hierarchy (see below for valid values),
-
status - HTTP status code (the same which you'll get in response
HTTP header),
-
more_info - url pointing to a more detailed description of the
error (or, more probably, to the page you're now reading).
Depending on the values on the reason_stack, the error
dictionary may contain additional keys. Currently possible values of the
reason_stack include:
-
["bad_request"] - you've made a bad request.
Subclasses:
-
[ "bad_request", "missing_parameter"] - you didn't
supply a required parameter. Extra keys:
- parameter - the name of the missing parameter.
-
[ "bad_request", "invalid_parameter"] - one of your
parameters has an invalid value. Extra keys:
- parameter - the name of the parameter,
-
whats_wrong_about_it - a string, pretty
self-explanatory,
-
["invalid_oauth_request"] - you've tried to use OAuth, but
your request was invalid.
Subclasses:
-
[ "invalid_oauth_request", "unsupported_oauth_version"]
- you have tried to use unsupported OAuth version (OKAPI
requires OAuth 1.0a).
-
[ "invalid_oauth_request", "missing_parameter"] - you
didn't supply a required parameter. Extra keys:
- parameter - the name of the missing parameter.
-
[ "invalid_oauth_request", "unsupported_signature_method"]
- you tried to use an unsupported OAuth signature method (OKAPI
requires HMAC-SHA1).
-
[ "invalid_oauth_request", "invalid_consumer"] - your
consumer does not exist.
-
[ "invalid_oauth_request", "invalid_token"] - your
token does not exist. This error is pretty common! Your token
may have expired (in case of request tokens) or may have been
revoked (in case of access tokens). You should ask your user to
redo the authorization dance.
-
[ "invalid_oauth_request", "invalid_signature"] -
your request signature was invalid.
-
[ "invalid_oauth_request", "invalid_timestamp"] - you
used a timestamp which was too far off, compared to the current
server time. This error is pretty common, especially if your
app is for mobile phones! You may ask your user to fix his
clock, or you could use the provided extra keys
to adjust your oauth_timestamp parameter yourself. Extra
keys:
-
yours - UNIX timestamp you have supplied (this
used to be a string, but now it is being casted to an
integer, see
here),
- ours - UNIX timestamp on our server,
-
difference - the difference, in seconds (to be
added to your clock),
- threshold - the maximum allowed difference.
-
[ "invalid_oauth_request", "nonce_already_used"] -
most probably, you have supplied the same request twice (user
double-clicked something?). Or, you have some error in the
nonce generator in your OAuth client.
In most cases, you should be fine with catching just the following (order
significant):
- ["invalid_oauth_request", "invalid_token"] (reauthorize),
- ["invalid_oauth_request", "invalid_timestamp"] (adjust the timestamp),
- any other 4xx status exception (send yourself a bug report).
-
All other errors - including HTTP 5xx responses, JSON parsing errors,
timeouts etc. - should be treated as connection errors (ask the user to
try later).
Important backward compatibility note: If Z is a subclass of X, then
it will forever stay a subclass of X. However, class X won't necessarilly stay
Z's direct parent. This means that ["x", "z"] may become ["x",
"y", "z"] or even ["w", "x", "y", "z"] one day. In other words,
instead writing if (reason_stack == ["x", "z"]) { ... } you should
rather use if ("z" in reason_stack) { ... }.
Differences between Opencaching sites
Client developers should be aware that there are some differences between
Opencaching sites. E.g. Opencaching.US currently does not support OKAPI log
image upload, but is the only site that provides "podcast geocaches".
OKAPI implements several mechanisms that either level those differences -
you don't need to care about them - or allows your application to automatically
adjust to the Opencaching site's capabilities.
OKAPI versions
Now and then, new features are added to OKAPI. They will be listed in the
Changelog, including version numbers. Applications
may compare those numbers to the installation's current OKAPI version number,
as returned by the site's
services/apisrv/installation
method, to detect if a new feature is available.
Site capabilities
OKAPI methods generally are designed to abstract from differences between OC
installations. E.g. if some geocache or log property is not implemented, OKAPI
still allows to request it, but will return null or false (as
explained in the method docs). When submitting data, unsupported options are
mostly ignored (as documented), or OKAPI will return an HTTP 200 result with
the success=false field and a user-friendly explanation (as
documented).
However, when searching for caches or submitting content, there are some
exceptions where developers may need to know about the site's capabilities.
The docs then will refer to one of the following methods, that your application
can call to find out what features are available:
These methods also return information that allows to hide nonfunctional
options from user interfaces. E.g. you may want to disable searching for
geocaches by rating, if OKAPI would ignore the user's input (because the OC
site does not implement ratings).
Branch tags
Throughout the OKAPI documentation, you will encounter options and fields
that are tagged as "OCPL" or "OCDE". These tags have the following meaning:
-
OCDE - This feature
currently is only in use at Opencaching sites that are based on the
OCDE software branch (currently Opencaching.DE/IT/FR). If your
application is NOT intended to be used with those sites, you may want
to skip this feature and not implement it.
-
OCPL - This feature
currently is only in use at Opencaching sites that are based on the
OCPL software branch (currently Opencaching.PL, NL, US, UK, RO). If
your application is NOT intended to be used with those sites, you
may want to skip this feature and not implement it.
In all other us cases, you are recommended to ignore the branch tags. See
above for more information on differences between Opencaching sites.
If you have any questions about this, then ask them
here.
How can I participate in OKAPI development?
OKAPI is Open Source and everyone is welcome to participate in the development.
We have our issue tracker.
You can use it to contact us!
You may also contact some of
the developers
directly, if you want.
Visit project homepage for details:
https://github.com/opencaching/okapi/
List of available methods
OKAPI web services (methods) currently available on this server:
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