An interesting Java interview question asked in most of the interviews while discussing topic on web services. There are basically two approaches in making web service: -
1) WSDL first Implemention second: In this case the Web service definition language XML is made first and using the same the web service bean classes are generated which implement the necessary functionality
Since WSDL defines Contract this is also known as Contract first
2)Implementation first WSDL second: This approach is used whenever legacy code is available which needs to be exposed as service. So here implementation is already available and hence only contract needs to be created using WSDL.
Following is the introductory video on Webservice for the one’s who are new to this topic: -

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