Java and XML

Output of XML Validation

Make sure your XML document, DTD, copyright file (if you created one), and compiled classes are assembled. You may then run the example program, and you might be surprised at the output (shown in Example 5.5).

Example 5-5. SAXParserDemo Output

D:\prod\JavaXML> java SAXParserDemo D:\prod\JavaXML\contents\contents.xml
Parsing XML File: D:\prod\JavaXML\contents\contents.xml


    * setDocumentLocator(  ) called
Parsing begins...
**Parsing Error**
  Line:    13
  URI:     file:/D:/prod/JavaXML/contents/contents.xml
  Message: Document root element "JavaXML:Book", must match DOCTYPE root 
           "JavaXML:Book".

This rather cryptic error is a significant problem when using DTDs and namespaces together. The error seems to be stating that the root specified in the DOCTYPE declaration (JavaXML:Book) does not match the root element of the document itself. But the root element is JavaXML:Book, right? Actually, it’s not! By default, SAX 2.0 specifies that parsers must enable their namespace feature, making all SAX 2.0 parsers namespace-aware unless this feature is explicitly set to false.^[3] We did not change this default, so our XMLReader implementation is namespace aware. The unexpected result of this is that our root element is seen (by the parser) as Book, with the namespace prefix of JavaXML. But remember that XML 1.0 and DTDs cannot distinguish between a prefix and element name, so the root element the DTD expects to find is JavaXML:Book. When it finds Book, it reports the error above.

The ...