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| JAXP API using DOM Parser |
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Main classes of javax.xml.parsers package for
the DOM:
| Classes |
Description |
| DocumentBuilder |
Defines the API to
obtain DOM
Document
instances from an
XML document. |
| DocumentBuilderFactory |
Defines a factory
API that enables
applications to
obtain a parser
that produces
DOM object trees
from XML
documents |
The diagram here shows the JAXP APIs to
process xml document using the DOM parser:
Understanding DOM Parser
At the very first, javax.xml.parsers.Document BuilderFactory class creates the instance of
DocumentBuilder. Through which it produces
a Document (a DOM) that conforms to the DOM
specification. The System property determines
the builder at the run time using javax.xml.parsers.DocumentBuilderFactory (it
selects the factory implementations to produce
the builder). The platform’s default value i.e.
system property can be overridden from the
command line.
Another method of DocumentBuilder as
newDocument() can also be used implementing
org.w3c.dom.Document interface that creates an empty Document.
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Alternatively, one of the builder’s parse
methods can be used to create a Document
from existing XML data. As a result, a DOM
tree like that shown in the diagram.
Creating Blank DOM Document
The following code creates a blank document:
//Create instance of DocumentBuilderFactory
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
//Get the DocumentBuilder
DocumentBuilder parser =
factory.newDocumentBuilder();
//Create blank DOM Document
Document doc =
parser.newDocument(); |
The class DocumentBuilderFactory is
responsible for creating new DOM parsers. The
instance of the class DocumentBuilder is used
to create a blank document. The newDocument() method of the class returns
a blank DOM document.
Creating DOM Child Elements
Once new document has been created, you
can add the element to it. First element of the
document is called the root element; another
elements added to the document are called
child elements of the root.
The following steps generate a DOM document
having root and child elements.
(1) Creating the root element
As you have seen above that how to create a
blank DOM document using DocumentBuilder object. The following code creates a blank
document.
//Create blank DOM Document
Document doc = docBuilder.newDocument();
The createElement method is used to create
the root element and appendChild method is |
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Mar 2008 | Java Jazz Up | 19
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