JSON-RPC 2.0 Implementation

Posted by Tristan Waddington on Dec 5, 2009 in Blog, Braindump, Web Development | 0 comments

Here’s another quick braindump post. A custom JSON-RPC library I wrote for a project at my last job. It should follow the JSON-RPC 2.0 Spec pretty closely. It does require the jQuery library as well.

You can pretty much ignore the MIKU references. Basically it’s just a way of namespacing objects to make them globally available. Try reading up on the YUI library for more information.

As always, feel free to post with any questions.

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var MIKU;
 
/*
 * Method to allow namespacing of new objects within MIKU;
 *
 * Example:
 * MIKU.namespace('objectname');
 * MIKU.objectname = function() { return {'...'} }
 *
 */
MIKU = function() {
  return {
    namespace: function(name) {
      try {
        if (MIKU[name]) {
          throw 'Namespace exists.';
        }
        return {}
      }
      catch (e) {
        this.throwError(e);
      }
    }
  }
}();
 
MIKU.namespace('throwError');
 
/*
 * Method to catch MIKU errors
 */
MIKU.throwError = function(e) {
  if (console) {
    console.error((e.message || 'MikuError:'), e);
  }
};
 
/*
 * Init the JsonRpc namespace into the MIKU object.
 */
MIKU.namespace('JsonRpc');
 
/*
 * Miku Json-RPC Implementation
 */
 
MIKU.JsonRpc = function() {
  var _url = 'json-rpc/call';
  var _timeout = false;
  var _requests = [];
  var _responses = [];
  var _callbacks = {};
  var _requestId = 0;
  var _failures = 0;
 
  function _send() {
    _request();
    _t = false;
    _requests = [];
  }
 
  function _request() {
    try {
      if (!_url) {
        throw('undefined post url.');
      }
      $.ajax({
        type: 'POST',
        url: _url,
        data: ({
          request: JSON.stringify(_requests)
        }),
        dataFilter: function(data, type) {
          //check for php errors
          try {
            return JSON.parse(data);
          }
          catch (e) {
            var phpError = /^.*?(Error|Warning|Notice).*?\:\s*(.*?) in .*?(\/[0-9A-Za-z\/\.\-\_\ ]+).* on line .*?([0-9]+).*$/i;
            var lines = data.split(/\n/g);
            $.each(lines, function() {
              var error = this.match(phpError);
              if (error) {
                MIKU.throwError({
                  message: error[1] + ': ' + error[2],
                  file: error[3],
                  line: error[4]
                });
              }
            });
          }
        },
        success: function(data) {
          _success(data);
        },
        error: function(XMLHttpRequest, textStatus, errorThrown) {
          // retry after connection failures
          if (XMLHttpRequest.status != '200') {
            _failures ++;
            if (_failures < 3) {
              _request();
              return;
            }
          }
 
          // give up and throw errors...
          MIKU.throwError([XMLHttpRequest, textStatus, errorThrown]);
        }
      });
    }
    catch(e) {
      MIKU.throwError(e);
    }
  }
 
  function _success(response) {
    $.each(jQuery.makeArray(response), function() {
      try {
        if (this.error) {
          // check for error
          throw(this.error);
        }
        else if(this.result) {
          // trigger callback
          var callback = _callbacks[this.id];
          callback(this.result);
        }
      }
      catch(e) {
        MIKU.throwError(e);
      }
    });
 
    // reset callbacks
    _callbacks = {};
  }
 
  function _genId() {
    return ++_requestId;
  }
 
  return {
    version: '2.0',
    delay: 10,
    setUrl: function(url) {
      _url = url;
    },
    call: function(args) {
      var id = _genId();
 
      var request = {
        jsonrpc: this.version,
        method: args.method,
        params: args.params,
        id: id
      }
 
      _requests.push(request);
      _callbacks[id] = args.onSuccess;
 
      if (_timeout) {
        clearTimeout(_timeout);
      }
      _timeout = setTimeout(_send, this.delay);
 
      return request;
    }
  }
}();
 
/*
 * Testing Below
 */
 
$(document).ready(function() {
  var rpc = MIKU.JsonRpc;
 
  rpc.call({
    method: 'System.getTitle',
    params: [
      'id_13'
    ],
    onSuccess: function(result) {
      console.debug(result);
    }
  });
});

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