Web Service Method in Ajax

Question

Hi What is Web Service Method in Ajax?

Hemant Kumar · Answer

Popularized through its use in a number of well-known Web application services like GMail Google Maps Flickr and Odeo.com Ajax provides Web developers with a way of expanding the value and function of their Web applications by using asynchronous XML messaging. The Web Services JavaScript Library introduced here expands on the fundamental mechanisms that power the Ajax pattern by introducing support for invoking SOAP-based Web services. Web services in the browser Invoking SOAP Web services from within a Web browser can be a tricky exercise particularly because the most popular Web browsers each handle generating and processing of XML in slightly different ways. There are few standard APIs or capabilities for XML processing that all browsers implement consistently. One of the mechanisms that browser implementers agree on is the XMLHttpRequest API which is at the heart of the Ajax design pattern. Thoroughly described in another recently published paper on developerWorks written by Philip McCarthy XMLHttpRequest is a Javascript object that you can use to perform asynchronous HTTP requests. The paper describes a sequence diagam (see Figure 1 ) that is very help in understanding how the XMLHttpRequest object enables the Ajax design (see Resources for a link to the full paper). Figure 1. Philip McCarthy's Ajax Roundtrip sequence diagram From this diagram you can see exactly how the XMLHttpRequest object functions. Some piece of JavaScript running within the Web browser creates an instance of the XMLHttpRequest and a function that serves as an asynchronous callback. The script then uses the XMLHttpRequest object to perform an HTTP operation against a server. When a response is received the callback function is invoked. Within the callback function the returned data can be processed. If the data happens to be XML the XMLHttpRequest object will automatically parse that data using the browser's built in XML processing mechanisms. Unfortunately it's in the details of how the XMLHttpRequest object automatically parses the XML where the primary difficultly with the Ajax approach comes into play. For instance suppose that the data that I am requesting is a SOAP envelope that contains elements from a number of different XML Namespaces and I want to grab the value of the attr attribute on the yetAnotherElement . (See Listing 1 .) refer this links http://www.codeproject.com/KB/ajax/Ajax_and_Web_Services.aspx