Apress, 2006.), which includes examples
of accessing the Amazon.com, Google, eBay, and Yahoo web services.
Introducing Web Services
A web service is a piece of functionality that is exposed through a web interface using standard
Internet protocols such as HTTP. The messages exchanged by the client and the server are
encoded using an XML-based protocol named Simple Object Access Protocol (SOAP) or by
using Representational State Transfer (REST) and are sent to the server over the HTTP protocol.
REST uses carefully crafted URLs with specific name-value pairs to call specific methods
on the servers. REST is considered to be the easiest way to communicate with the web services
that expose this interface. When using REST to access a web service, you simply make an HTTP
GET request, and you??™ll receive the response in XML format.
SOAP is an XML-based standard for encoding the information transferred in a web service
request or response. SOAP is fostered by a number of organizations, including powerful companies
such as Microsoft, IBM, and Sun.
The beauty of using web services is that the client and the server can use any technology,
any language, and any platform. As long as they exchange information with a standard protocol
such as SOAP over HTTP, there is no problem if the client is a cell phone and the server is
a Java application running on Solaris, for example.
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