Web Services, Part II: Calling Service Methods
Loading the Web Service URL
A Web service is identified by a URL. The following is an example for a valid Web service:
It is quite cumbersome to use this URL every time you need to reference the Web service. The
useService() method establishes a friendly name for a Web service URL, which can be referenced later from within the code. Here is the formal syntax:
sElementID.useService(sWebServiceURL, sFriendlyName [, oUseOptions]);
IDof the element to which the
WebServicebehavior is attached. This parameter is required.
WebServiceURL. This parameter is required. The path can be of four different types:
- Web service file. It has an
.asmxfile extension. This short form of the URL is sufficient, provided that the Web service is located in the same folder as the Web page using the
WebServicebehavior. In this case, the
?WSDLquery string is assumed by the behavior.
- WSDL file name. A Web Services Description Language (WSDL) file name. The WSDL file must have a
- Full file path. A full path to a Web service (
.asmx) or WSDL (
.wsdl) file. A file path to a Web Service must include the
?WSDLquery string. Either a local file path or a URL can be specified.
- Relative path. A relative path to a Web service (
.asmx) or WSDL (
.wsdl) file. A file path to a Web service must include the
sFriendlyNameis a string representing a friendly name for the Web service URL. This parameter is required.
oUseOptionsis an instance of the
useOptionsobject. It has a single property,
reuseConnection, that specifies the persistence of the connection information required by Web services that use Secure Sockets Layer (SSL) authentication.
The following line assigns a friendly name to a Web service file (
echoService.asmx must reside in the same folder as the Web page that calls the
WebService behavior. Same rule applies when you call the WSDL file:
The following line assigns a friendly name to a local disk file:
webServiceCallerBody.useService( "D:\legacy\yehuda\uyehuda\column97\ echoService.asmx?WSDL","echo");
You have to add the
?WSDL query string also when you have a full HTTP path:
webServiceCallerBody.useService( "http://www.webreference.com/js/column97/ echoService.asmx?WSDL","echo");
Suppose now that the Web service
.asmx file is two levels up from the Web page (relative path):
And finally, here is an example for an
.asmx file residing in a subfolder beneath the Web page:
To ensure that the
useService method works correctly, you should place it inside an event handling function for the
onload event. In this way, you will ensure that the first attempt to call a method in the behavior occurs only after the page has been downloaded and parsed. The event handling function may define friendly names for one or more Web Services. Here is an example:
Next: How to send a message to a Web service