queryreadstore.js

这是一个ajax的例子大家好好的看看就是一个鱼眼的效果

				if(requestObject.onComplete && !aborted){
					var subset = null;
					if (!requestObject.onItem) {
						subset = items.slice(startIndex, endIndex);
					}
					requestObject.onComplete.call(scope, subset, requestObject);   
				}
			};
			this._fetchItems(request, _fetchHandler, _errorHandler);
			return request;	// Object
		},
	
		getFeatures: function(){
			return this._features;
		},
	
		close: function(/*dojo.data.api.Request || keywordArgs || null */ request){
			// I have no idea if this is really needed ... 
		},
	
		getLabel: function(/* item */ item){
			//	summary:
			//		See dojo.data.api.Read.getLabel()
			if(this._labelAttr && this.isItem(item)){
				return this.getValue(item, this._labelAttr); //String
			}
			return undefined; //undefined
		},
	
		getLabelAttributes: function(/* item */ item){
			//	summary:
			//		See dojo.data.api.Read.getLabelAttributes()
			if(this._labelAttr){
				return [this._labelAttr]; //array
			}
			return null; //null
		},
		
		_fetchItems: function(request, fetchHandler, errorHandler){
			//	summary:
			// 		The request contains the data as defined in the Read-API.
			// 		Additionally there is following keyword "serverQuery".
			//
			//	The *serverQuery* parameter, optional.
			//		This parameter contains the data that will be sent to the server.
			//		If this parameter is not given the parameter "query"'s
			//		data are sent to the server. This is done for some reasons:
			//		- to specify explicitly which data are sent to the server, they
			//		  might also be a mix of what is contained in "query", "queryOptions"
			//		  and the paging parameters "start" and "count" or may be even
			//		  completely different things.
			//		- don't modify the request.query data, so the interface using this
			//		  store can rely on unmodified data, as the combobox dijit currently
			//		  does it, it compares if the query has changed
			//		- request.query is required by the Read-API
			//
			// 		I.e. the following examples might be sent via GET:
			//		  fetch({query:{name:"abc"}, queryOptions:{ignoreCase:true}})
			//		  the URL will become:   /url.php?name=abc
			//
			//		  fetch({serverQuery:{q:"abc", c:true}, query:{name:"abc"}, queryOptions:{ignoreCase:true}})
			//		  the URL will become:   /url.php?q=abc&c=true
			//		  // The serverQuery-parameter has overruled the query-parameter
			//		  // but the query parameter stays untouched, but is not sent to the server!
			//		  // The serverQuery contains more data than the query, so they might differ!
			//
	
			var serverQuery = request.serverQuery || request.query || {};
			//Need to add start and count
			if(!this.doClientPaging){
				serverQuery.start = request.start || 0;
				// Count might not be sent if not given.
				if (request.count) {
					serverQuery.count = request.count;
				}
			}
			if(!this.doClientSorting){
				if(request.sort){
					var sort = request.sort[0];
					if(sort && sort.attribute){
						var sortStr = sort.attribute;
						if(sort.descending){
							sortStr = "-" + sortStr;
						}
						serverQuery.sort = sortStr;
					}
				}
			}
			// Compare the last query and the current query by simply json-encoding them,
			// so we dont have to do any deep object compare ... is there some dojo.areObjectsEqual()???
			if(this.doClientPaging && this._lastServerQuery!==null &&
				dojo.toJson(serverQuery)==dojo.toJson(this._lastServerQuery)
				){
				fetchHandler(this._items, request);
			}else{
				var xhrFunc = this.requestMethod.toLowerCase()=="post" ? dojo.xhrPost : dojo.xhrGet;
				var xhrHandler = xhrFunc({url:this.url, handleAs:"json-comment-optional", content:serverQuery});
				xhrHandler.addCallback(dojo.hitch(this, function(data){
					data = this._filterResponse(data);
					if (data.label){
						this._labelAttr = data.label;
					}
					var numRows = data.numRows || -1;
	
					this._items = [];
					// Store a ref to "this" in each item, so we can simply check if an item
					// really origins form here (idea is from ItemFileReadStore, I just don't know
					// how efficient the real storage use, garbage collection effort, etc. is).
					dojo.forEach(data.items,function(e){ 
						this._items.push({i:e, r:this}); 
					},this); 
					
					var identifier = data.identifier;
					this._itemsByIdentity = {};
					if(identifier){
						this._identifier = identifier;
						for(i = 0; i < this._items.length; ++i){
							var item = this._items[i].i;
							var identity = item[identifier];
							if(!this._itemsByIdentity[identity]){
								this._itemsByIdentity[identity] = item;
							}else{
								throw new Error(this._className+":  The json data as specified by: [" + this.url + "] is malformed.  Items within the list have identifier: [" + identifier + "].  Value collided: [" + identity + "]");
							}
						}
					}else{
						this._identifier = Number;
						for(i = 0; i < this._items.length; ++i){
							this._items[i].n = i;
						}
					}
					
					// TODO actually we should do the same as dojo.data.ItemFileReadStore._getItemsFromLoadedData() to sanitize
					// (does it really sanititze them) and store the data optimal. should we? for security reasons???
					numRows = (numRows === -1) ? this._items.length : numRows;
					fetchHandler(this._items, request, numRows);
				}));
				xhrHandler.addErrback(function(error){
					errorHandler(error, request);
				});
				// Generate the hash using the time in milliseconds and a randon number.
				// Since Math.randon() returns something like: 0.23453463, we just remove the "0."
				// probably just for esthetic reasons :-).
				this.lastRequestHash = new Date().getTime()+"-"+String(Math.random()).substring(2);
				this._lastServerQuery = dojo.mixin({}, serverQuery);
			}
		},
		
		_filterResponse: function(data){
			//	summary:
			//		If the data from servers needs to be processed before it can be processed by this
			//		store, then this function should be re-implemented in subclass. This default 
			//		implementation just return the data unchanged.
			//	data:
			//		The data received from server
			return data;
		},
	
		_assertIsItem: function(/* item */ item){
			//	summary:
			//		It throws an error if item is not valid, so you can call it in every method that needs to
			//		throw an error when item is invalid.
			//	item: 
			//		The item to test for being contained by the store.
			if(!this.isItem(item)){
				throw new Error(this._className+": Invalid item argument.");
			}
		},
	
		_assertIsAttribute: function(/* attribute-name-string */ attribute){
			//	summary:
			//		This function tests whether the item passed in is indeed a valid 'attribute' like type for the store.
			//	attribute: 
			//		The attribute to test for being contained by the store.
			if(typeof attribute !== "string"){ 
				throw new Error(this._className+": Invalid attribute argument ('"+attribute+"').");
			}
		},
	
		fetchItemByIdentity: function(/* Object */ keywordArgs){
			//	summary: 
			//		See dojo.data.api.Identity.fetchItemByIdentity()
	
			// See if we have already loaded the item with that id
			// In case there hasn't been a fetch yet, _itemsByIdentity is null
			// and thus a fetch will be triggered below.
			if(this._itemsByIdentity){
				var item = this._itemsByIdentity[keywordArgs.identity];
				if(!(item === undefined)){
					if(keywordArgs.onItem){
						var scope =  keywordArgs.scope?keywordArgs.scope:dojo.global;
						keywordArgs.onItem.call(scope, {i:item, r:this});
					}
					return;
				}
			}
	
			// Otherwise we need to go remote
			// Set up error handler
			var _errorHandler = function(errorData, requestObject){
				var scope =  keywordArgs.scope?keywordArgs.scope:dojo.global;
				if(keywordArgs.onError){
					keywordArgs.onError.call(scope, error);
				}
			};
			
			// Set up fetch handler
			var _fetchHandler = function(items, requestObject){
				var scope =  keywordArgs.scope?keywordArgs.scope:dojo.global;
				try{
					// There is supposed to be only one result
					var item = null;
					if(items && items.length == 1){
						item = items[0];
					}
					
					// If no item was found, item is still null and we'll
					// fire the onItem event with the null here
					if(keywordArgs.onItem){
						keywordArgs.onItem.call(scope, item);
					}
				}catch(error){
					if(keywordArgs.onError){
						keywordArgs.onError.call(scope, error);
					}
				}
			};
			
			// Construct query
			var request = {serverQuery:{id:keywordArgs.identity}};
			
			// Dispatch query
			this._fetchItems(request, _fetchHandler, _errorHandler);
		},
		
		getIdentity: function(/* item */ item){
			//	summary: 
			//		See dojo.data.api.Identity.getIdentity()
			var identifier = null;
			if(this._identifier === Number){
				identifier = item.n; // Number
			}else{
				identifier = item.i[this._identifier];
			}
			return identifier;
		},
		
		getIdentityAttributes: function(/* item */ item){
			//	summary:
			//		See dojo.data.api.Identity.getIdentityAttributes()
			return [this._identifier];
		}
	}
);

}