connection.js

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/*
Copyright (c) 2006, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
Version: 0.11.3
*/

/**
 * The Connection Manager provides a simplified interface to the XMLHttpRequest
 * object.  It handles cross-browser instantiantion of XMLHttpRequest, negotiates the
 * interactive states and server response, returning the results to a pre-defined
 * callback you create.
 * @ class
 */
YAHOO.util.Connect =
{
/**
   * Array of MSFT ActiveX ids for XMLHttpRequest.
   * @private
   * @type array
   */
	_msxml_progid:[
		'MSXML2.XMLHTTP.3.0',
		'MSXML2.XMLHTTP',
		'Microsoft.XMLHTTP'
		],

  /**
   * Object literal of HTTP header(s)
   * @private
   * @type object
   */
	_http_header:{},

  /**
   * Determines if HTTP headers are set.
   * @private
   * @type boolean
   */
	_has_http_headers:false,

 /**
  * Determines if a default header of
  * Content-Type of 'application/x-www-form-urlencoded'
  * will be added to any client HTTP headers sent for POST
  * transactions.
  * @private
  * @type boolean
  */
    _use_default_post_header:true,

 /**
  * Determines if a default header of
  * Content-Type of 'application/x-www-form-urlencoded'
  * will be added to any client HTTP headers sent for POST
  * transactions.
  * @private
  * @type boolean
  */
    _default_post_header:'application/x-www-form-urlencoded',

 /**
  * Property modified by setForm() to determine if the data
  * should be submitted as an HTML form.
  * @private
  * @type boolean
  */
    _isFormSubmit:false,

 /**
  * Property modified by setForm() to determine if a file(s)
  * upload is expected.
  * @private
  * @type boolean
  */
    _isFileUpload:false,

 /**
  * Property modified by setForm() to set a reference to the HTML
  * form node if the desired action is file upload.
  * @private
  * @type object
  */
    _formNode:null,

 /**
  * Property modified by setForm() to set the HTML form data
  * for each transaction.
  * @private
  * @type string
  */
    _sFormData:null,

 /**
  * Collection of polling references to the polling mechanism in handleReadyState.
  * @private
  * @type object
  */
    _poll:{},

 /**
  * Queue of timeout values for each transaction callback with a defined timeout value.
  * @private
  * @type object
  */
    _timeOut:{},

  /**
   * The polling frequency, in milliseconds, for HandleReadyState.
   * when attempting to determine a transaction's XHR readyState.
   * The default is 50 milliseconds.
   * @private
   * @type int
   */
     _polling_interval:50,

  /**
   * A transaction counter that increments the transaction id for each transaction.
   * @private
   * @type int
   */
     _transaction_id:0,

  /**
   * Member to add an ActiveX id to the existing xml_progid array.
   * In the event(unlikely) a new ActiveX id is introduced, it can be added
   * without internal code modifications.
   * @public
   * @param string id The ActiveX id to be added to initialize the XHR object.
   * @return void
   */
	setProgId:function(id)
	{
		this._msxml_progid.unshift(id);
	},

  /**
   * Member to enable or disable the default POST header.
   * @public
   * @param boolean b Set and use default header - true or false .
   * @return void
   */
	setDefaultPostHeader:function(b)
	{
		this._use_default_post_header = b;
	},

  /**
   * Member to modify the default polling interval.
   * @public
   * @param {int} i The polling interval in milliseconds.
   * @return void
   */
	setPollingInterval:function(i)
	{
		if(typeof i == 'number' && isFinite(i)){
			this._polling_interval = i;
		}
	},

  /**
   * Instantiates a XMLHttpRequest object and returns an object with two properties:
   * the XMLHttpRequest instance and the transaction id.
   * @private
   * @param {int} transactionId Property containing the transaction id for this transaction.
   * @return connection object
   */
	createXhrObject:function(transactionId)
	{
		var obj,http;
		try
		{
			// Instantiates XMLHttpRequest in non-IE browsers and assigns to http.
			http = new XMLHttpRequest();
			//  Object literal with http and tId properties
			obj = { conn:http, tId:transactionId };
		}
		catch(e)
		{
			for(var i=0; i<this._msxml_progid.length; ++i){
				try
				{
					// Instantiates XMLHttpRequest for IE and assign to http.
					http = new ActiveXObject(this._msxml_progid[i]);
					//  Object literal with http and tId properties
					obj = { conn:http, tId:transactionId };
					break;
				}
				catch(e){}
			}
		}
		finally
		{
			return obj;
		}
	},

  /**
   * This method is called by asyncRequest to create a
   * valid connection object for the transaction.  It also passes a
   * transaction id and increments the transaction id counter.
   * @private
   * @return object
   */
	getConnectionObject:function()
	{
		var o;
		var tId = this._transaction_id;

		try
		{
			o = this.createXhrObject(tId);
			if(o){
				this._transaction_id++;
			}
		}
		catch(e){}
		finally
		{
			return o;
		}
	},

  /**
   * Method for initiating an asynchronous request via the XHR object.
   * @public
   * @param {string} method HTTP transaction method
   * @param {string} uri Fully qualified path of resource
   * @param callback User-defined callback function or object
   * @param {string} postData POST body
   * @return {object} Returns the connection object
   */
	asyncRequest:function(method, uri, callback, postData)
	{
		var o = this.getConnectionObject();

		if(!o){
			return null;
		}
		else{
			if(this._isFormSubmit){
				if(this._isFileUpload){
					this.uploadFile(o.tId, callback, uri);
					this.releaseObject(o);
					return;
				}

				//If the specified HTTP method is GET, setForm() will return an
				//encoded string that is concatenated to the uri to
				//create a querystring.
				if(method == 'GET'){
					uri += "?" +  this._sFormData;
				}
				else if(method == 'POST'){
					//If POST data exists in addition to the HTML form data,
					//it will be concatenated to the form data.
					postData = (postData?this._sFormData + "&" + postData:this._sFormData);
				}
				this._sFormData = '';
			}

			o.conn.open(method, uri, true);

			if(this._isFormSubmit || (postData && this._use_default_post_header)){
				this.initHeader('Content-Type', this._default_post_header);
				if(this._isFormSubmit){
					this._isFormSubmit = false;
				}
			}

			if(this._has_http_headers){
				this.setHeader(o);
			}

			this.handleReadyState(o, callback);
			o.conn.send(postData?postData:null);

			return o;
		}
	},

  /**
   * This method serves as a timer that polls the XHR object's readyState
   * property during a transaction, instead of binding a callback to the
   * onreadystatechange event.  Upon readyState 4, handleTransactionResponse
   * will process the response, and the timer will be cleared.
   *
   * @private
   * @param {object} o The connection object
   * @param callback User-defined callback object
   * @return void
   */
    handleReadyState:function(o, callback)
    {

		var oConn = this;

		if(callback && callback.timeout){
			this._timeOut[o.tId] = window.setTimeout(function(){ oConn.abort(o, callback, true); }, callback.timeout);
		}

		this._poll[o.tId] = window.setInterval(
			function(){
				if(o.conn && o.conn.readyState == 4){
					window.clearInterval(oConn._poll[o.tId]);
					delete oConn._poll[o.tId];

					if(callback && callback.timeout){
						delete oConn._timeOut[o.tId];
					}

					oConn.handleTransactionResponse(o, callback);
				}
			}
		,this._polling_interval);
    },

  /**
   * This method attempts to interpret the server response and
   * determine whether the transaction was successful, or if an error or
   * exception was encountered.
   *
   * @private
   * @param {object} o The connection object
   * @param {object} callback - User-defined callback object
   * @param {boolean} determines if the transaction was aborted.
   * @return void
   */
    handleTransactionResponse:function(o, callback, isAbort)
    {
		// If no valid callback is provided, then do not process any callback handling.
		if(!callback){
			this.releaseObject(o);
			return;
		}

		var httpStatus, responseObject;

		try
		{
			if(o.conn.status !== undefined && o.conn.status != 0){
				httpStatus = o.conn.status;
			}
			else{
				httpStatus = 13030;
			}
		}
		catch(e){
			// 13030 is the custom code to indicate the condition -- in Mozilla/FF --
			// when the o object's status and statusText properties are
			// unavailable, and a query attempt throws an exception.
			httpStatus = 13030;
		}

		if(httpStatus >= 200 && httpStatus < 300){
			try
			{
				responseObject = this.createResponseObject(o, callback.argument);
				if(callback.success){
					if(!callback.scope){
						callback.success(responseObject);
					}
					else{
						// If a scope property is defined, the callback will be fired from
						// the context of the object.
						callback.success.apply(callback.scope, [responseObject]);
					}
				}
			}
			catch(e){}
		}
		else{
			try
			{
				switch(httpStatus){
					// The following case labels are wininet.dll error codes that may be encountered.
					case 12002: // Server timeout
					case 12029: // 12029 to 12031 correspond to dropped connections.
					case 12030:
					case 12031:
					case 12152: // Connection closed by server.
					case 13030: // See above comments for variable status.
						responseObject = this.createExceptionObject(o.tId, callback.argument, (isAbort?isAbort:false));
						if(callback.failure){
							if(!callback.scope){
								callback.failure(responseObject);
							}
							else{
								callback.failure.apply(callback.scope, [responseObject]);
							}
						}
						break;
					default:
						responseObject = this.createResponseObject(o, callback.argument);
						if(callback.failure){
							if(!callback.scope){
								callback.failure(responseObject);
							}
							else{
								callback.failure.apply(callback.scope, [responseObject]);
							}
						}
				}
			}
			catch(e){}
		}