Creating Web Services from existing applications

So you want to enter the brave new world of Distributed Computing. But you have a huge baggage of existing applications that you can't throw away. Not to worry! This article will show you the various options available to leverage those existing applications and still not miss the technology bus.

Web services are the logical next step in the evolution of e-business.

The new era of distributed computing is all about using Internet technologies and standards to create applications that span the globe, cutting across time zones and cultures, and serving diverse markets. The Web services vision is one where everything is viewed as a service that can be dynamically discovered and consumed, using messaging on the network. Businesses can sell their services to others by publishing them on the Web.

Enterprises have made significant investments in older applications that were developed when there were no open standards. These applications use proprietary technologies that are not interoperable with each other. These applications will continue to be useful in the future and cannot be discarded.

Existing applications are also quite complex in nature. For example, a payroll system developed in the US may take into account certain US labor laws when doing its processing. The same application, when offered worldwide, has to offer a more generic interface so that users from other countries can be accommodated. These interfaces also have to be simplified to allow for maximum flexibility.

Lets say, Company ABC has an inventory management system sitting on a mainframe computer. This system provides up-to-date information about the company's product lines and items in stock. The company's sales representatives need to have real-time access to this information to perform their functions more effectively.

The company has a Windows 2000 Advanced Server with the Dot Net Runtime installed. This server is connected to the Internet and through the firewall, to the internal network of the company. To enable Internet access to the mainframe legacy application, we need to build Web Service Adapters that will expose the application's functionality through the <link> Simple Object Access Protocol (SOAP) <link>.

A Web Service Adapter is a wrapper program that will talk to the legacy application using its native protocol at one end, and talk to the rest of the world using SOAP, at the other end.

The Web Service Adapter can be built using Microsoft VisualStudio.NET that makes creation of Web Services a snap. Since a typical inventory application will have a lot of functionalities, a number of such web service adapters need to be created, each exposing a specific functionality. These web services will be published using the Web Services Description Language (WSDL).

The company's sales representatives will use applications that access this web service over the internet using a simple URL like http://www.abc.com/services/inventory/CurrentOrders.asmx. The web server will transfer the request to the web services adapter, which, through the Dot Net runtime, will talk to the legacy application and return the required data. This whole process will be totally transparent to the end user. The company's legacy application will be now employed gainfully to reap all the benefits of the internet-enabled applications without having to start from scratch.

We at Stylus, with our deep understanding of how the web works, can help enterprises migrate their legacy applications to the web painlessly and effectively. We work on the cutting edge web technologies and bring our rich experience of developing effective enterprise solutions, to help you realize your goals.

Useful Links:

http://www-106.ibm.com/developerworks/webservices/library/ws-legacy/

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