JsonRpcContrib.txt

%META:TOPICINFO{author="ProjectContributor" comment="" date="1454519814" format="1.1" version="1"}%
---+!! %TOPIC%
%SHORTDESCRIPTION%

%TOC%

---++ Summary
This package implements a [[http://en.wikipedia.org/wiki/JSON-RPC][JSON-RPC 2.0]] protocol to interface
with Foswiki and its plugins. 

In contrast to the normal REST interface of Foswiki, a JSON-RPC interface
offers well defined calling semantics for requests and responses. The
interface will also take care that any received data is recoded
to the server's character encoding. JSON-RPC is normally called as part of
some !JavaScript AJAX application.

<nop>%TOPIC% also comes with a jQuery plugin to simplify working with
JSON-RPC. This is a simple wrapper around jQuery's own
AJAX capabilities.

---++ Registering JSON-RPC procedures
Foswiki plugins are able to register their own handler for a specific
method in a given namespace, thus:

<verbatim>
use Foswiki::Contrib::JsonRpcContrib ();

sub initPlugin {
    ...
    Foswiki::Contrib::JsonRpcContrib::registerMethod(
        "MyNamespace", 
        "someMethod", 
        \$jsonRpcSomeMethod
    );
    ...
}

# Plugin's implementation
sub jsonRpcSomeMethod {
    my ($session, $request) = @_;
    ...
   # Return some result
   return $result;
}
</verbatim>

---++ Handler functions
The handler function in your plugin takes two parameters, =$session= and =$request=. =$session= is a reference to the Foswiki session; most implementers should simply ignore this. =$request= is a reference to the JSON request object. The following methods are available on this object:
   * =param('param1')= - returns the value of a single named parameter
   * =params()= - returns a reference to the entire parameter hash
   * =method()= - returns the method
   * =namespace()= - returns the namespace
The handler function can return a scalar or a reference to an acyclic graph (a tree structure). The structure may contain blessed data (perl objects) if (and only if) those objects implement the =TO_JSON= method described in the documentation for the CPAN JSON module.

Errors can be signalled using a simple =die=. Such errors will be returned to the caller with an =errorCode= of 1. If you need to pass back extended error information, you will have to encode it in the =die= message.

---++ Calling using a POST
Once a handler is registered it may be called using an URL of the format:

=%SCRIPTURL{"jsonrpc"}%/MyNamespace=

... while POSTing a JSON-encoded request according to the JSON-RPC 2.0 specification,
like,

<verbatim>
{
  jsonrpc: "2.0", 
  method: "someMethod", 
  params: {
     topic: "Web.Topic",
     ...
     param1: "value1",
     param2: "value2",
     ...
  }, 
  id: "caller's id"
}
</verbatim>

---++ Calling using jQuery
The jQuery plugin can be used by requesting it via
=%<nop>JQREQUIRE{"jsonrpc"}%=. JSON-RPC can now be called like this:

<verbatim>
$.jsonRpc(
  endpoint, /* %SCRIPTURL{"jsonrpc"}% */
  {
    namespace: "MyNamespace",
    method: "someMethod",
    id: "some caller's id",
    params: {
     topic: "Web.Topic",
     ...
     param1: "value1",
     param2: "value2", 
    },
    beforeSend: function(xhr) { ... },
    error: function(jsonResponse, textStatus, xhr) { ... },
    success: function(jsonResponse, textStatus, xhr) { ... }
  }
);
</verbatim>

---++ Error response

If the procedure fails for any reason the JSON response will have the format

<verbatim>
{
  jsonrpc: "2.0",
  error: {
    code: errorCode,
    message: "error description"
  },
  id: "caller's id"
}
</verbatim>

The following error codes are defined:
   * -32700: Parse error - Invalid JSON was received by the server.
   * -32600: Invalid Request - The JSON sent is not a valid Request object.
   * -32601: Method not found - The method does not exist / is not available.
   * -32602: Invalid params - Invalid method parameter(s).
   * -32603: Internal error - Internal JSON-RPC error.
   * -32099 to -32000: Server error - Reserved for implementation-defined server-errors.
   * 1: unknown error - a =die= in the handler will return this
   * 401: access denied - returned if provided credentials are incorrect

---++ Success response

If the call is successful the JSON response will be of the format:

<verbatim>
{
   jsonrpc: "2.0",
   result: some-result-object,
   id: "caller's id"
}
</verbatim>

---++ Authentication
If there is an existing login session then JSON-RPC calls will be authenticated using that session. Alternatively, requests can be authenticated by passing in =username= and =password= URL parameters. It is strongly recommended that this is only done if the communications links is secure (https:), as these parameters are sent in plain text.

---++ Extensions to the standard

JSON-RPC 2.0 normally only allows you to pass parameters to a remote
procedure using a well formed request object as described
above. However in real-live web applications, data to be transmitted to
a specific endpoint is most conveniently sent using URL parameters (as is
the case for normal HTML forms).

Instead of requiring all form fields to be converted into a
JSON-RPC request object on the client side, the JsonRpcContrib
converts form data to a proper request object transparently. 
This way you can call a JSON-RPC function using a simple form submission
from the client.

The called namespace and method can thus be specified much like a
subject/verb url to a REST interface. These calls are equivalent:

<verbatim>
$.jsonRpc(
  "%SCRIPTURL{"jsonrpc"}%" 
  namespace: "MyNamespace",
  method: "someMethod",
  ...
);
</verbatim>

<verbatim>
$.jsonRpc(
  "%SCRIPTURL{"jsonrpc"}%/MyNamespace",
  method: "someMethod",
  ...
);
</verbatim>

<verbatim>
$.jsonRpc(
  "%SCRIPTURL{"jsonrpc"}%/MyNamespace/someMethod" 
  ...
);
</verbatim>

You can also use an HTML form:

<verbatim>
<form action="%SCRIPTURL{"jsonrpc"}%" method="post">
<input type="hidden" name="namespace" value="MyNamespace" />
<input type="hidden" name="method" value="someMethod" />
...
</form>
</verbatim>

<verbatim>
<form action="%SCRIPTURL{"jsonrpc"}%/Mynamespace" method="post">
<input type="hidden" name="method" value="someMethod" />
...
</form>
</verbatim>

<verbatim>
<form action="%SCRIPTURL{"jsonrpc"}%/Mynamespace/someMethod" method="post">
...
</form>
</verbatim>

Forms of this type can easily be sent to the server using %SYSTEMWEB%.JQueryForm's =$.ajaxSubmit()= method.

If a namespace, method, or parameters are specified as part of a JSON-RPC request object as well as using URL parameters, the URL parameters take higher precedence and are merged into the request object.

---++ Installation Instructions

%$INSTALL_INSTRUCTIONS%

---++ Info
<!--
   * Set SHORTDESCRIPTION = %$SHORTDESCRIPTION%
-->

|  Change History: | <!-- versions below in reverse order -->&nbsp; |
|  03 Feb 2016: (2.24) | Foswikitask:Item13405: Add NFC normalization of Unicode strings. |
|  14 Jul 2015: (2.23) | fixed encoding of compressed responses Foswikitask:Item13521 |
|  14 Jun 2015: (2.22) | Release with Foswiki 2.0.<br />\
                  Foswikitask:Item13378: Implement UNICODE support,<br />\
                  Foswikitask:Item13323: Use /usr/bin/env perl.<br />\
                  Foswikitask:Item13412: Don't utf-8 encode response |
|  29 Jan 2015: | Foswikitask:Item13238: fix content-type of response |
|  17 Dec 2014: | Foswikitask:Item13164: added support for gzip compression of http response<br />\
                  Foswikitask:Item13125: CGI changes for multi_param calls<br />\
                  Foswikitask:Item13065: Log jsonrpc events to Foswiki event.log |
|  28 Aug 2014: | don't use DEBUG constant to toggle local debug messages as it conflicts with Assert.pm |
|  11 Dec 2013: | removed dependency on JSON::XS |
|  30 May 2013: | added support for serialising objects, and rewrote some of the documentation (Foswiki:Main/CrawfordCurrie) |
|  20 Mar 2013: | added feature to define handlers in !LocalSite.cfg (Config.spec) so that pure contribs can implement backends now |
|   1 Oct 2012: | added the async flag to the =$.jsonRpc= frontend to =$.ajax= |
|   2 Aug 2012: | fixed json2 not loaded in IE7 (Foswiki:Main/JanKrueger) |
|  16 Apr 2012: | fixed =jsonrpc= for apache's suexec |
|  10 Jan 2012: | fixed perl dependencies; \
                  added =redirectto= url parameter similar to the standard foswiki rest handler |
|  10 May 2011: | fixed jsonrpc script to work on old foswikis; \
                  fixed multi-value params; \
                  fixed compatibility with various JSON cpan libraries |
|  29 Apr 2011: | initial release |
|  Dependencies: | %$DEPENDENCIES% |

%META:FORM{name="PackageForm"}%
%META:FIELD{name="Author" title="Author" value="Michael Daum"}%
%META:FIELD{name="Version" title="Version" value="%25$VERSION%25"}%
%META:FIELD{name="Release" title="Release" value="%25$RELEASE%25"}%
%META:FIELD{name="Repository" title="Repository" value="https://github.com/foswiki/distro"}%
%META:FIELD{name="Copyright" title="Copyright" value="&copy; 2011-2016 Michael Daum http://michaeldaumconsulting.com and Foswiki Contributors"}%
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