The XMethods site is a portal which aims to promote Web Services. To this end, its three founders offer, free of charge, the possibility of using or offering Web Services of public interest with the aim of boosting their creation, deployment and use. Various SOAP implementations are available; these currently include a Java implementation, ApacheSOAP, and a Perl implementation, SOAP::Lite.
To be completely usable with most SOAP implementations, as XMethod suggests, a Web Service should provide a complete description which includes the following elements:
- SOAP End point URL: URL where the SOAP server receives the SOAP request
E.g.: http://www.server.com/rpcRouter
- SOAPAction: Some services may demand a SOAPAction Header
E.g.: urn:xmethodsSoapPing#pingHost
- Method Namespace URI: URI (Univeral Resource Identifier) of the object for which the method is called
E.g.: urn:StockQuoteEngine
- Method Name(s): Name of the available methods
E.g.: getStockQuote, getMarketCap
- WSDL URL: URL of a file which fully describes a service in WSDL format. The WSDL description is all that is needed to execute the service.
E.g.: http://www.server.com/stockquote.wsdl
- Instructions: Instructions for use of service
- Server Implementation: Writing environment necessary for interoperability
E.g.: SOAP::Lite for Perl v0.35
- Sample URL Client Code: Source code of the downloadable example
E.g.: http://www.server.com/sampleClient.java |
The examples shown on the XMethods site are very varied: translation using BabelFish Altavista, Verification of Domain Name, Ping Test, FedEx Package Tracking display of price of books at Barnes&Nobles.
Each service uses either the Perl implementation (SOAP::Lite) or the Java one (ApacheSOAP), but other initiatives have led to new listed implementations such as 4s4c.
For the majority of these services the code of the client example is available and ready for use. You simply need to configure your station using an appropriate implementation. This rapid and effective installation enables you to access SOAP services via a simple process, which consists in invoking a SOAP object which defines its end point, URI and the method to be called corresponding to the service requested.
We carried out interoperability tests between Java and Perl implementations and these proved conclusive. We will discuss these aspects in more detail in a later article.
In order to avoid the security restrictions imposed by certain companies, XMethods has made all its services available on port 80 (standard port for HTTP). In addition, XMethods tries as far as possible to provide the WSDL associated with each service, as more and more implementations rely on this description language to call Web Services.
