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A web service is a collection of protocols and standards used
for exchanging data between applications over the web. Web
services enable applications written with different programming
languages supported over varying platforms (different hardware,
software, database, or network platforms) to exchange data,
very conveniently.
Web services are a new breed of web technologies that offer a
platform and language-neutral approach. They are so cool that
a web service written in Java and running on BEA WebLogic
server can access a web service written in C and running on a
Microsoft IIS. All without a concern about, how each web
service is actually implemented.
Web Services have revolutionized the way; the Business
to Business and Business to Consumer services are provided
because they provide multiple functions, ranging from a simple
web request to a complicated business process.
A web service makes it easily available over the web and uses
a standardized XML messaging system as its core mechanism.
XML is used to encode all communications into a web
service. For example, a client invokes a web service by
sending an XML message, then waits for a corresponding XML
response. Because all communication is in XML, web services
are not tied to any one operating system or programming
language. So Java can talk with Perl and windows applications
can talk with Unix applications
Web Services: Distributed Computing environment
Web Services have gradually evolved from the basic Remote
Procedure Calls. But unlike RPCs they use XML as a core
ingredient for communication. Web Service concerns about
three specific things:
• A mechanism to find and register a service.
• A transport mechanism to access a service.
• A mechanism for two parties to communicate and define
the input-output parameters for a service.
What are Web Services
These properties, when coupled together, provide a new form of
Distributed Computing Environment. It requires standard
definition mechanisms, lookup services, and transport definitions
using protocols like SOAP. These all are provided without
concern for the underlying implementation mechanism.
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Distributed Computing Environment: web scenario
Service provider: First and foremost a service provider is
required to host any number of exposed Web Services.
Service repository: Secondly, a centralized service repository
is required for publishing information that clients can use
to find information about published Web Services.
And finally, various mechanisms are required to locate and
access the services.
Let’s look at the figure in general and understand what’s going
on.
• Firstly, a service provider publishes a service to an external
repository. Once such a service has been exported to a
registry, it can then be used by a client.
• Client look- ups a service from a repository and receives
information about a service. Information, such as the format
of the procedure calls and the address of a service provider,
would normally be provided, amongst other details.
• At last, the client is bind to the underlying services and
then accesses that service (functionality the service
provides).
Web Services: Core specifications
XML: a key player: Web Services at its core uses a fundamental
set of functionality based on XML (it is a wonderful
technology, and it has really found a home in Web Services).
XML provides a user-defined meta language that represents
data and the sets of validating rules. XML has become an
excellent vehicle for packing data over the distributed network
such that both ends of the pipe easily exchange and understand
the data.
XML provides a meta language in which you can write specialized
languages to express complex interactions between
clients and services. Behind the facade of a web server, the
XML message gets converted to a middleware request and the
results are converted back to XML. |
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July 2007 | Java Jazz Up | 35 |
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| Pages: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, |
| 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53 , Download PDF |
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