JsonRpcContrib < System

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---+!! %TOPIC%
%FORMFIELD{"Description"}%

%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
You do not need to install anything in the browser to use this extension. The following instructions are for the administrator who installs the extension on the server.

Open configure, and open the "Extensions" section. Use "Find More Extensions" to get a list of available extensions. Select "Install".

If you have any problems, or if the extension isn't available in =configure=, then you can still install manually from the command-line. See http://foswiki.org/Support/ManuallyInstallingExtensions for more help.


---++ Dependencies
<table border="1" class="foswikiTable"><tr><th>Name</th><th>Version</th><th>Description</th></tr><tr><td align="left">JSON</td><td align="left">&gt;=2.59</td><td align="left">Required.</td></tr></table>

---++ Change History
|  04 Apr 2016: (2.26) | Foswikitask:Item14025: Fix issues with JSON::XS 3.02 in some environments. |
|  18 Mar 2016: (2.25) | Foswikitask:Item14011: Make sure HTTP2 is always compressing. |
|  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 |
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Author	Michael Daum
Version	2.26
Release	4 Apr 2016
Description	JSON-RPC interface for Foswiki
Repository	https://github.com/foswiki/distro
Copyright	© 2011-2016 Michael Daum http://michaeldaumconsulting.com and Foswiki Contributors
License	GPL (Gnu General Public License)
Home	http://foswiki.org/Extensions/JsonRpcContrib
Support	Foswiki:Support/JsonRpcContrib
Topic revision: r1 - 04 Apr 2016, ProjectContributor
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