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WebServices

Hi
  I am new to web services.If some one says that i have to write web services for the EJB. What does that mean?Could you please suggest some online tutorials for webservices.Some basic definitions are highly appreciated like
what are webservices?
What they are used for ?
What other technologies i need to learn to write web services?
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koppcha
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koppcha
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bloodredsunCommented:
Hey koppcha,

>>what are webservices?

From wikipedia: "A web service is a collection of protocols and standards used for exchanging data between applications. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet, in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Java and Python, or Windows and Linux applications) is due to the use of open standards. OASIS and the W3C are the steering committees responsible for the architecture and standardization of web services."

Basically they allow you to transmit standardised xml between apps to communicate, call methods etc..

>>What they are used for ?
As above, they allow disparate technologies (Java/.NET) on different OS's (Win32/*nix) to communicate easily, so you can have two completely different apps communicating with each other in a seamless and standardised manner. I'm currently using one from Actuate for pdf report generation. The api is based on web services and allows us to put the app on any server and call it from any other.

>>What other technologies i need to learn to write web services?
The configuration is all xml based (WDSL, SOAP etc) and there's the Java stack required, either Axis from apache or the ibm ws toolkit. The best place is the axis website http://ws.apache.org/axis/ and there are some good tutorials.
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koppchaAuthor Commented:
Hi BloodRedSun
   Thanks for the information.Do you know about this
>>If some one says that i have to write web services for the EJB

What do you think i need to do ?
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bloodredsunCommented:
Write the web service as you would any presentation layer client for the EJB. In some ways it depends on what the EJB does and what it is, but basically you are exposing the public methods of the EJB as a web service. This means that if the EJB performs business logic of some kind, that you are then publishing these methods as a web service so that other clients may use it.

In your case, web services is just another layer between the client and the EJB. Where in the past your EJB would be looked up from a JNDI call in the JSP/servlet/action, you are now wrapping it in a ws so that it may be called by other apps on different servers. It is one way of interoperation between .NET and J2EE as you could have a .NET front end calling a J2EE EJB via the ws.

Firstly, you need to get your head arround ws, which means a couple of examples like a stock ticker via a basic ws (such as jws files). This is a pretty good book as an introduction http://www.amazon.com/exec/obidos/tg/detail/-/1861007531/qid=1115421703/sr=8-7/ref=sr_8_xs_ap_i4_xgl14/102-9652094-7685714?v=glance&s=books&n=507846 (I did my first web services from this) and while it's not perfect, it's not a bad start.
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koppchaAuthor Commented:
Thank you very much bloodredsun.
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koppchaAuthor Commented:
Hi Bloodredsun
   How long webservices is in the industry ? Is it a new technology or its there in the industry for a while ?
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bloodredsunCommented:
>>How long webservices is in the industry ? Is it a new technology or its there in the industry for a while ?

Only a couple of years. It's only recently gone from the over-hyped phase (when everyone says "use web services for everything" )to actually being used for somehting useful.
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