About Web services
Web services allow you to use preexisting components (available
on the Internet or on a local network) instead of writing new business
logic to perform common tasks invoked by the applications that you
develop. Web services originated when the Simple Object Access Protocol
(SOAP) was introduced. SOAP leverages Extensible Markup Language
(XML) and usually employs Hypertext Transfer Protocol (HTTP) as
the transport. Invoking Web services through SOAP requires serialization
and deserialization of datatypes, and the building and parsing of
SOAP messages.
Part of the value of Web
services comes from the Web Services Description Language (WSDL),
which enables a service to be self-describing. WSDL defines an XML
grammar for describing Web services as collections of communication
endpoints capable of exchanging messages. WSDL service definitions
provide documentation for distributed systems and serve as a recipe for
automating the details involved in applications communication.
With SOAP and WSDL, using third-party components is easier
because interfaces between applications become standardized across
disparate platforms.
PowerBuilder supports the following Web services standards:
-
SOAP 1.1 or later
-
WSDL 1.1 or later
-
HTTP or HTTPS
-
XSD (XML Schema Document) 1.0
Producing a Web service
PowerBuilder
provides tools for developing custom class (nonvisual) user objects
and deploying them as EAServer components
and exposing them as Web services. You can deploy a component to
an EAServer host running on Windows
and UNIX operating systems. For more information, see Chapter 23, “Building an EAServer Component.”