Page 204 - DCAP312_WEB_TECHNOLOGIES_II

Web Technologies-II

Notes • SOAP/WSDL-based: In traditional web service models, web service interfaces are exposed
through WSDL documents (a type of XML), which have URLs. Subsequent message
exchange is in SOAP, another type of XML document.
• RESTful Web Services:

1. REST-based ( “RESTful”) web services are collections of web resources identified by
URIs. Every document and every process is modeled as a web resource with a unique
URI. These web resources are manipulated by the actions that can be specified in an
HTTP header. Neither SOAP, nor WSDL, nor WS-standards are used. Instead, message
exchange can be conducted in any format—XML, JSON, HTML, etc. In many cases a
web browser can serve as the client.
2. REST is a suitable technology for applications that do not require security beyond what
is available in the HTTP infrastructure and where HTTP is the appropriate protocol.
REST services can still deliver sophisticated functionality. Flickr, Google Maps and
Amazon all provide RESTful web services. NetBeans IDE Software as a Service (SaaS)
functionality lets you use Facebook, Zillow, and other third-party-provided services
in your own applications.
• SOAP-based Web Services: In SOAP-based web services, Java utilities create a WSDL
file based on the Java code in the web service. The WSDL is exposed on the net. Parties
interested in using the web service create a Java client based on the WSDL. Messages are
exchanged in SOAP format. The range of operations that can be passed in SOAP is much
broader than what is available in REST, especially in security.

10.1 Web Services

A Web Service is a component written in any language, deployed on any platform, which has
a standard wrapping layer based on XML. Other services have to be able to discover the Web
Service and invoke it dynamically.
Web Services are applications with two characteristics.
First, a web service publishes, and is defined by, an application programming interface (API)
for the functionality it makes available to external callers.
Second, a web service is accessed over a network by using the hypertext transfer protocol
(HTTP).Web services enable interoperability between software systems, and are the foundation
for modern service oriented architecture (SOA).
XML Web Services using the .NET platform and ASP.NET. It begins with an overview of the
.NET framework and an explanation of the process behind XML Web Services, and then quickly
delves into building and consuming Web Services. Included will be discussions of proxies,
classes, SOAP, Global XML Web Services Architecture, WSDL, UDDI, and Disco.
The general workflow is shown below.
This new technology, initiated by IBM and Microsoft, then partially standardized under the
aegis of the W3C, is unanimously accepted throughout the computing industry. It is this; above
all, that makes Web Services a revolutionary technology.

The purely technical aspects are not fundamentally innovative. What makes the architecture
of Web Services so attractive, in much the same way as XML, is its simplicity, readability and
that it is built on existing standards.

198 LOVELY PROFESSIONAL UNIVERSITY