Java Examples in a Nutshell, 3rd Edition

Parsing and Manipulating with JAXP and DOM

Example 19-1 used the SAX API for parsing XML documents. We now turn to another commonly used parsing API: the DOM, or Document Object Model. The DOM API is a standard defined by the World Wide Web Consortium (W3C); its Java implementation consists of the org.w3c.dom package and its subpackages. The current version of the DOM standard is Level 2. As of this writing, the DOM Level 3 API is making its way through the standardization process at the W3C.

The Document Object Model defines the API of a parse tree for XML documents. The org.xml.dom.Node interface specifies the basic features of a node in this parse tree. Subinterfaces, such as Document, Element, Entity, and Comment, define the features of specific types of nodes. A program that uses the DOM parsing model is quite different from one that uses SAX. With the DOM, you have the parser read your entire XML document and transform it into a tree of Node objects. Once parsing is complete, you can traverse the tree to find the information you need. The DOM parsing model is useful if you need to make multiple passes through the tree, if you want to modify the structure of the tree, or if you need random access to an XML document, instead of the sequential access provided by the SAX model.

Example 19-2 is a listing of the program WebAppConfig.java. Like Example 19-1, WebAppConfig reads a web.xml web application deployment descriptor. This example uses a DOM parser to build a ...