Example of Event Mapping

As an example of how the event iterator API maps an XML stream, consider the following XML document:

<?xml version="1.0"?>
<BookCatalogue xmlns="http://www.publishing.org">
    <Book>
        <Title>Yogasana Vijnana: the Science of Yoga</Title>
        <ISBN>81-40-34319-4</ISBN>
        <Cost currency="INR">11.50</Cost>
    </Book>
</BookCatalogue>

This document would be parsed into eighteen primary and secondary events, as shown in Table 18–3. Note that secondary events, shown in curly braces ({}), are typically accessed from a primary event rather than directly.

version="1.0"

isCData = false
data = "\n"
IsWhiteSpace = true

qname = BookCatalogue:http://www.publishing.org
attributes = null
namespaces = {BookCatalogue" -> http://www.publishing.org"}

qname = Book
attributes = null
namespaces = null

qname = Title
attributes = null
namespaces = null

isCData = false
data = "Yogasana Vijnana: the Science of Yoga\n\t"
IsWhiteSpace = false

qname = Title
namespaces = null

qname = ISBN
attributes = null
namespaces = null

isCData = false
data = "81-40-34319-4\n\t"
IsWhiteSpace = false

qname = ISBN
namespaces = null

qname = Cost
attributes = {"currency" -> INR}
namespaces = null

isCData = false
data = "11.50\n\t"
IsWhiteSpace = false

qname = Cost
namespaces = null

isCData = false
data = "\n"
IsWhiteSpace = true

qname = Book
namespaces = null

isCData = false
data = "\n"
IsWhiteSpace = true

qname = BookCatalogue:http://www.publishing.org
namespaces = {BookCatalogue" -> http://www.publishing.org"}

There are several important things to note in this example:

• The events are created in the order in which the corresponding XML elements are encountered in the document, including nesting of elements, opening and closing of elements, attribute order, document start and document end, and so forth.

• As with proper XML syntax, all container elements have corresponding start and end events; for example, every StartElement has a corresponding EndElement, even for empty elements.

• Attribute events are treated as secondary events, and are accessed from their corresponding StartElement event.

• Similar to Attribute events, Namespace events are treated as secondary, but appear twice and are accessible twice in the event stream, first from their corresponding StartElement and then from their corresponding EndElement.

• Character events are specified for all elements, even if those elements have no character data. Similarly, Character events can be split across events.

• The StAX parser maintains a namespace stack, which holds information about all XML namespaces defined for the current element and its ancestors. The namespace stack, which is exposed through the javax.xml.namespace.NamespaceContext interface, can be accessed by namespace prefix or URI.