Introduction to JBUILDER9 Web Services

WebService is a software model that is invoked over a network, especially the Internet, to perform a broken sequence or continuous task.

Developers can create a client application that invokes a series of Web services that provide some or most of the application logic through RPC or messaging services. Developers can locate a published Web service and use it as needed.

One example is the ability of a company to provide Web services to its customers, and to allow customers to check the inventory of the product before issuing an order. Another example is the ability of customers to track their deliveries with FedEx-provided Web services.

Web services use SOAP (Simple Object Access Protocol) to exchange SOAP messages with transport protocols such as HTTP. A SOAP message is actually an XML document that is passed in a Web service and call.

Web services can be written in any language and run on any platform. The client of a Web service can write in any language, and it can run on any platform. For example, a Web service that runs on a Windows platform and writes with Dephi can be invoked by a Java-written service on a Linux platform.

Web Service Architecture

The Web services architecture allows developers of services to expose all levels of business functionality, in other words, a Web service can be very simple, such as returning the current temperature, or it can be a complex application. Schemas also allow multiple services to be combined with a new feature application.

Web services have three separate roles, service providers, service requesters, service agents. Service providers create services and provide them to customer applications. The service requester may also be a customer of multiple services. Agent, is to provide a way such as service registration, so that service providers and service requesters can interact with the service.

Three roles interact through the publication, lookup, and binding of a service. The service provider notifies the agent that the service exists by giving the customer access to the service by using the agent's publishing interface. The publishing information describes the service and describes where the service is positioned. The service requester asks for the location of the agent service. Depending on the service information obtained from the agent, the requester can bind or invoke the service. The following diagram summarizes how the three interact.

Web service Standards

Web service development is based on standards that include some technology. The main is soap,wsdl (Web Services Description Language), UDDI (generic description, Discovery, integration) and Wsil (Web Service Check language).

Soap

Soap is an independent transport message protocol. Each SOAP message is an XML document. SOAP uses a one-way message, although it may be synthesized by a queue that requests a reply. The SOAP specification defines the format of an XML message, regulates its easy HTTP protocol routing, but does not regulate its content and how it is actually passed.

Each SOAP document has a root element. This root element, the first element in the document, contains all the other elements in the document. There are two parts in it: The message header and the message body. The message header contains routing or content data, which may be empty. The message body includes an actual message, or it may be empty.

The following is a simple example of a SOAP message that is transmitted via HTTP at the current Borland share price.

Post/stockquote http/1.1

Host:www.stockquoteserver.com

Content-type:text/xml; charset= "Utf-8"

content-length:nnnn

SOAPAction: "Urn:stock-quote-services"

xmlns:soap-env= "http://schemas.xmlsoap.org/soap/envelope/"

soap-env:encodingstyle= "http://schemas.xmlsoap.org/soap/encoding/" >