call a webservice via http get

[quentin compson]

say that i have a page that when the url is invoked writes xml to the
screen. another application calls that page, parses the xml and does
something with it. is that a web service?

if not, then when a web service is used via http get, then what is
different about that?

 

[quentin compson]

scenario #1

Not in the commonly used sense, no.



Well, since a web service call transmits a body of XML in the request,
it's not like a comomn GET request at all.

then how is it different from scenario #1 outlined above (i.e. ...when the
url is invoked writes xml to the screen...)?

 

[Omar Khan]

scenario #1




then how is it different from scenario #1 outlined above (i.e. ...when the
url is invoked writes xml to the screen...)?

Peace be unto you.

Think of it like RMI, but not too hard.
RMI can only be used with Java to Java applications or
so I believe.
Webservice allows applications written in Java to communicate
with applications written with C# or python or something.
Now that does not mean you can not do the same thing
with socket programming and yet-another-way of
object serialization.
However, when someone has to maintain your code or
you want another language to interface with your service
someone has to learn the original programmer's method of
object serialization and transportation.
The point of web services is to establish a set of
open
standards to
make the programmer's life easy.
By the way it is not limited to http only, you can use ftp
or whatever.

So what are the standards.
Well for applications to communicate with each other,
they need to serialize their payloads, usually objects in this age.
XML comes in play since it is plain text, so even ancient
languages like COBOL can communicate.
Namespaces and XSD lend their hands to provide
datatypes and structure rules.
SOAP provides a simple, extensible protocol
for exchanging XML messages. A Soap message
has a common format like an Rss feed has a common
format
http://blogs.law.harvard.edu/tech/rss.
Now a company may have many web services
and each one is written in a standard XML
file called a WSDL file(Web Services Description Language),
http://api.google.com/GoogleSearch.wsdl
almost like a contract that a programmer has to follow
to interface.
To look up web services for a particular company or industry
you use something called UDDI (Universal Description, Discovery and
Integration). Think of UDDI as a registry where
companies can list themselves in a well defined manner
like the yellow pages or something.
Now since these files are structured and follow rules and
can be easily read, there are many tools out there that can go
through the different layers and
can automatically list a company and it's webservice (UDDI), and
provide an automatically generated interface (from the WSDL file)
to use the web service over the web or something like java.

Examples

Newsgroups
Message-ID: <[email protected]>
http://groups.google.ca/groups?safe...ws04.bloor.is.net.cable.rogers.com>&lr=&hl=en
Message-ID: <[email protected]>
http://groups.google.ca/groups?safe...ws04.bloor.is.net.cable.rogers.com>&lr=&hl=en


http://www.w3.org/2002/ws/Activity
http://java.sun.com/webservices/index.jsp