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Chapter 29. WebLogic Server and XML Technologies

by Subramanian H Kovilmadam


Today's enterprise applications seldom function in isolation. Different systems communicate with each other and pass data between each other to perform business functions. For example, consider a reservation system that books airline tickets. The system is functionally aware of the process for booking airline tickets, but it knows nothing about the process involved in charging the customer's credit card for the tickets booked. So, it communicates with the bank's application to charge the amount to the credit card. The bank application does what it does best: charge the card. We have several independent systems working with each other for an enterprise to function. That having been said, there's no way to guarantee that the different applications will use similar definitions for their data structures. For that matter, we can't even guarantee that different applications are written using the same programming language. So, how do these systems communicate with each other? In other words, is there a standard mechanism for data transfer between different heterogeneous systems in the enterprise?

A typical solution for the problem at hand is that the technical designers of both the reservation and the payment systems assemble in a conference room and discuss what data elements should be sent to the banking system to enable a credit card payment. Assume that the bank requires that the credit card number, type, and expiration date, along with the amount, for making a payment. If the payment goes through successfully, the bank returns a message along with an authorization number. If the payment fails, the bank returns a text message indicating the reason why the card failed.

After the data elements have been identified, the next thing that must be ironed out is the format in which the data will be sent.

In this chapter, we look at some of the basic XML technologies available to the developer. We touch on XML DTDs and schemas and look at various parsing techniques. We also learn how to transform an XML document into another XML document, or even an HTML document, by using transformation.

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