Bottom up vs Top down Web services development

Bottom up approach

Bottom-up Web services development involves creating a Web service from a Java bean or enterprise bean.

Although bottom-up Web service development may be faster and easier, especially if you are new to Web services, the top-down approach is the recommended way of creating a Web service.

When creating a Web service using a bottom-up approach, first you create a Java bean or EJB bean and then use the Web services wizard to create the WSDL file and Web service.

Top Down

In Top Down approach , business logic first. A contract on business side is finalized and then WSDL is made based on that based on business requirements.WSDL to Java based tools generate necessary files .Top-down Web services development involves creating a Web service from a WSDL file.

When creating a Web service using a top-down approach, first you design the implementation of the Web service by creating a WSDL file. You can do this using the WSDL Editor. You can then use the Web services wizard to create the Web service and skeleton Java classes to which you can add the required code.

In this way you have more control over how business logic is being handled by creating WSDL first

Although bottom-up Web service development may be faster and easier, especially if you are new to Web services, the top-down approach is the recommended way of creating a Web service. By creating the WSDL file first you will ultimately have more control over the Web service, and can eliminate interoperability issues that may arise when creating a Web service using the bottom-up method.

However from final consumer point of view this can be a pain. For example they will not get the data in the format in which they require , they might have to do lot of manipulations , calculations to ultimately consume the data.

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I have seen fight when you are not in WSDL side , IT people who are at consumer side want that WSDL should directly provide us this data in format in which they can consume easily.

The bottom up approach generates web services for which the design is driven from an application point of view (developer driven) and will not address the need for other consumers.

Some useful Websites with pros and cons on Top and Bottom up approach

http://www.infoq.com/news/2010/07/top-down-bottom-up-soa

http://oracled.wordpress.com/2009/12/25/developing-web-service-top-down-vs-bottom-up-approach/

http://technologyandleadership.com/top-down-vs-bottom-up-soa/