In this post I am going to walk through writing and consuming JSON services using ASP.Net, WCF, and jQuery to request the stock price for a company.
Visual Studio 2010 Web Application Project Template Additions
jQuery Intellisense – let Visual Studio write your jQuery for you
AJAX-enabled WCF Service – item template that auto-generates the web.config entries for configuring a JSON service to be consumed and proxied by an ASP.Net ScriptManager
Targeted web.config files – easy way to manage different service endpoints for different environments
What is JSON?
Java Script Object Notation – JSON is a subset of the object literal notation of JavaScript. Since JSON is a subset of JavaScript, it can be used in the language with no muss or fuss.
var dog ={color:"grey",name:"Spot", size:46};
SOAP Bloat
SOAP services are extremely verbose. This verbosity enables us to use tools like Visual Studio’s built-in ”Add Service Reference” to auto-generate client proxy classes. The following examples demonstrate the XML that is used for requesting a stock price and the corresponding response:
The above example when formatted as JSON is as follows:
GET Request
ticker=GOOG
JSON Response
{"d":534.5}
JSON Enabling a WCF Service
Using the AJAX-enabled WCF Service item template pretty much does it all. An additional step can be taken to eliminate the need for the additions to the web.config by configuring the channel factory directly on the service declaration (.svc) file:
Decorate the operation (service method) with the WebGetAttribute to enable the use of HTTP GET for data retrieval and return the response as JSON :
[WebGet(ResponseFormat = WebMessageFormat.Json)]
Our resulting stock price service’s code behind will look like the following:
[ServiceContract(Namespace= JsonWcfDemoNamespace.Value)]publicclass StockPriceService
{// To use HTTP GET, add [WebGet] attribute. (Default ResponseFormat is WebMessageFormat.Json)// To create an operation that returns XML,// add [WebGet(ResponseFormat=WebMessageFormat.Xml)],// and include the following line in the operation body:// WebOperationContext.Current.OutgoingResponse.ContentType = "text/xml";[OperationContract][WebGet(ResponseFormat=WebMessageFormat.Json)]public StockPrice GetStockPrice(string ticker){...}// Add more operations here and mark them with [OperationContract]}
Converting Text to JSON and Back
eval() – invokes the JavaScript compiler. The compiler will correctly parse the text and produce an object structure. The eval function is very fast. However, it can compile and execute any JavaScript program, so there can be security issues.
JSON.parse() – To defend against security issues with the eval function, it is preferred to use a JSON parser. A JSON parser will recognize only JSON text, rejecting all scripts. In browsers that provide native JSON support, JSON parsers are also much faster than eval. It is expected that native JSON support will be included in the next ECMAScript standard.
jQuery’s $.getJSON() Method
jQuery provides the getJSON method for easily making calls to services providing JSON-formatted responses and performing the JSON conversion. Its signature is as follows:
$.getJSON( url,[ data ],[ callback(data, textStatus)])
url – A string containing the URL to which the request is sent.
data – A map or string that is sent to the server with the request.
callback(data, textStatus) – A callback function that is executed if the request succeeds.
Consuming our stock price service using the getJSON method will look like the following:
$.getJSON("StockPriceService.svc/GetStockPrice",{ ticker: tickerValue },function(data, textStatus){if(textStatus !='success'||!data.d){
$("#stockPricePanel")
.html('<span class="error">Error looking up stock price. Did you enter a valid ticker?</span>');}else{var stockPrice = data.d;var isIncrease =(stockPrice.Delta>=0);var deltaStyle = isIncrease ?'gain':'loss';
$("#stockPricePanel")
.html('<span class="price">'+ stockPrice.Price+'</span>')
.append('<span class="delta '+ deltaStyle +'">'+ stockPrice.Delta+'</span>')
.append('<span class="percent '+ deltaStyle +'">('+ stockPrice.PercentChange+'%)</span>');}});
Working with WCF Serialized JSON Dates
One caveat when working with JSON is that WCF serializes DateTimes to JSON in the format:
/Date({milliseconds since 01/01/1970}-{time zone})/
Unfortunately, native JSON conversion does not automatically convert the date string to a JavaScript date object. The following method shows an example of how to convert a JSON date string to a javascript Date object:
function convertJSONToDate(json){returneval(json.replace(/\/Date\((.*?)\)\//gi,"new Date($1)"));}
For first time readers, Galleriffic is a jQuery photo gallery optimized to handle high volumes of photos while conserving bandwidth. h0bbel has posted a nice read on some of the benefits of Galleriffic over other photo gallery scripts.
New Features
Keyboard Navigation
Support for synchronized transitions (image cross-fades)
Ability to add or remove images after the gallery is initialized
Support for custom hash identifiers (when using history)
Better API to make it easier to customize
Smarter pagination
Integration with the jquery.history plugin for history support
Warnings to users attempting to upgrade from version 1.0
The onChange event in 1.0 has been renamed to onSlideChange.
All transition event handlers have new signatures, so you will need to make sure to update any transition event handlers you have implemented.
Using synchronized transitions requires changes to your stylesheet – primarily the additional of relative and absolutely positioning so that two images can occupy the same space at the same time.
There are now 5 examples, each builds on the previous. For a visual treat, check out the last example, whose colors I inverted.
For first time readers, Galleriffic is a jQuery photo gallery optimized to handle high volumes of photos while conserving bandwidth. h0bbel has posted a nice read on some of the benefits of Galleriffic over other photo gallery scripts.
New Features
Updated to work with jQuery 1.3 (apparently jQuery 1.3.2 introduces a flicker the gallery advances)
OnTransitionIn and OnTransitionOut events that allow for plugging in custom transitions
SlideShow auto start option
Disable history and url hash writing option
Support for showing an element (such as an animated loading image) when waiting for an image to load
Thumbnails are now simply shown/hidden instead of being rebuilt which allows for any custom html to be used as a thumbnail
Replaced invalid html attributes “description” and “original” with an optional caption element that can contain any custom html
Changed the toggle slideshow span to a hyperlink
By exposing both image and page transition events, the doors of creativity are now open for plugging in your own image transitions. This should also lend to a more modular approach for extending Galleriffic.
FAQ
Will Galleriffic generate the slide and thumbnail images automatically?
I have been asked a lot if Galleriffic automatically generates the thumbnails and slides.
Galleriffic by itself does not do any image processiong or generation; however, there is a great tool that does: jAlbum. I have created a jAlbum skin that I use myself for creating my personal galleries. After installing jAlbum and the Galleriffic jAlbum skin, simply choose your source image directory and an output directory, click “Make Album”, and wallah, you now have a complete html gallery with 3 different size versions of each image.
With the stylesheet used in the example, each thumbnail is floated left, and thus as many thumbnails that will fit in the width of the column will be displayed. If you want fewer or more columns, make the width of the navigation panel smaller or larger. I am currently setting its width using javascript with the following line in the html:
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