There’s no escape from Extensible Markup Language (XML) these days. It’s everywhere: in configuration files, messages between servers, web pages, even databases. Wherever there’s structured data, XML is often found close by.
As I mentioned earlier, JSP pages can generate any type of text, including XML. In the simplest case, the JSP page includes static XML elements as template text and a few actions to add the dynamic data, similar to the HTML examples in previous chapters. A more sophisticated page gets raw XML data from somewhere and transforms it to different XML formats depending on the type of browser making the request.
More and more, web applications also consume XML data generated by an external source, perhaps a database or another server. Such an application may extract price information from different vendors’ product catalogs, published as XML documents, and create a side-by-side comparison.
In this chapter we first look at the things you need to be aware of when generating XML responses with JSP, including device-dependent transformations, and then how to process XML data in different ways.
XML is a set of syntax rules for how to represent structured data using markup elements represented by an opening tag (optionally with attributes), a body and a closing tag:
<employee id="123"> <first-name>Hans</first-name> <last-name>Bergsten</last-name> <telephone>310-555-1212</telephone> </employee>
This XML example ...