In order to let our application do
something useful with XML data as it is being parsed, we must
handlers with the SAX parser. A handler
is nothing more than a set of callbacks that SAX defines to let us
interject application code at important events within a
document’s parsing. Realize that these events will take place
as the document is parsed, not after the parsing has occurred. This
is one of the reasons that SAX is such a powerful interface: it
allows a document to be handled sequentially, without having to first
read the entire document into memory. We will later look at the
Document Object Model (DOM), which has this limitation.
There are four core handler interfaces defined by SAX 2.0:
org.xml.sax.EntityResolver. In this chapter, we
ContentHandler, which allows standard
data-related events within an XML document to be handled, and take a
first look at
ErrorHandler, which receives
notifications from the parser when errors in the XML data are found.
DTDHandler will be examined in Chapter 5. We briefly discuss
EntityResolver at various points in the text; it
is enough for now to understand that
EntityResolver works just like the other handlers, and is built specifically for resolving external entities specified within an XML document. Custom application classes that perform specific actions within the parsing process can implement each of these interfaces. ...