< Day Day Up > |
Before you begin developing Web services, you should understand exactly what's going on behind the scenes with SOAP, WSDL, and UDDI. SOAPAll Web services use SOAP v1.1, a lightweight XML-based protocol optimized for use in distributed environments. SOAP v1.1 is designed to provide the necessary infrastructure and definition to support XML-based Remote Procedure Calls. SOAP v1.1 provides the following:
WSDLWSDL is the underpinning of how Web services are described to the outside world. Created by Microsoft and IBM in 2000, WSDL defines an XML grammar for describing network services and serves as a recipe for automating the details in application communication. Typically, WSDL describes a Web service's methods, inputs, and contact mechanism. These are the most important aspects of WSDL:
Web services are defined in terms of the endpoint, or service, that actually acts on or processes the Web service's request. These endpoints represent the actual methods being implemented and how they can be called. In reality, there are only two mechanisms for communicating with a Web service: one-way and bidirectional, depending on who originated the message. The WSDL specification defines four specific types of requests a Web service can support:
In fact, the only difference between one-way versus notification messages and request/response versus solicit/response messages is who generates and sends the message. For example, in a one-way message, the client makes a request, and the Web service acts on it without returning a status. In a notification message, the Web service makes a call back to the client without waiting for a response. As you shall see shortly, WebLogic Workshop provides mechanisms for quickly and easily developing Web services that support each request type. Although understanding WSDL is important, what's most important is knowing how WebLogic Workshop can build controls to access external Web services based on WSDL and generate WSDL based on controls. UDDIUDDI provides a mechanism for Web services developers to publish new and updated Web services and a mechanism for clients to find and access published Web services. UDDI enables businesses to publish and advertise the services they offer and describe how these services should be used. Web service functionality, as with most service-based functionality, is provided through a programming interface specified in WSDL. In a publish-and-find scenario, a developer publishes the existence of a service along with its definition, often referred to as a binding template . In a picture-printing service, for example, any number of companies could offer a service to print digital pictures. Binding templates contain one or more instances of a tModel , which represents interfaces supported by the service. The tModel might have been uniquely published by the service provider, with information on the interfaces and URL references to the WSDL document. At a minimum, a Web service must publish its business name and service information via business registry entries. A business registry can contain the following:
UDDI also supports a wide variety of other information about the service, such as compliance with a set of existing standards, usage details, transaction capabilities, and so forth.
|
< Day Day Up > |