23.1 Parsing XML Documents with DOM Level 2 1135
We use the Apache Xerces-J parser in this book. See
http://xml.apache.org/xerces-j/
. This parser also
comes with the complete DOM API in Javadoc format.
2. Download the Java API for XML Processing (JAXP). This API
provides a small layer on top of DOM that lets you plug in different
vendor’s parsers without making any changes to your basic code. See
http://java.sun.com/xml/
.
3. Set your
CLASSPATH
to include the DOM classes. In the case of
Apache Xerces, you need to include
xerces_install_dir\
xerces.jar
. For example, for desktop applications on Windows you
would do
set CLASSPATH=xerces_install_dir\xerces.jar;%CLASSPATH%
If you wanted to use DOM from servlets and JSP, you would copy the
appropriate JAR file to the server’s
lib
directory (if supported),
unpack the JAR file (using
jar -xvf
) into the server’s
classes
directory, or explicitly change the server’s
CLASSPATH
, usually by
modifying the server start-up script.
4. Set your
CLASSPATH
to include the JAXP classes. These classes
are in jaxp_install_dir/jaxp.jar
. For example, on Unix/Linux and
the C shell, you would do
setenv CLASSPATH jaxp_install_dir/jaxp.jar:$CLASSPATH
For use from servlets and JSP, see the preceding step.
5. Bookmark the DOM Level 2 and JAXP APIs. The official
DOM specification can be found at
http://www.w3.org/TR/
DOM-Level-2-Core/
, but the API in Javadoc format that comes
with Apache Xerces is easier to read and also includes the JAXP and
SAX (see Section 23.3) APIs.
6. Print the JAXP specification for your reference. Download it
from
http://java.sun.com/xml/jaxp-1_1-spec.pdf
.
Parsing
With DOM processing, there are two high-level tasks: turning an XML document
into a DOM data structure and looking through that data structure for the data that
interests you. The following list summarizes the detailed steps needed to accomplish
these tasks.
1. Tell the system which parser you want to use. This can be done in
a number of ways: through the
javax.xml.parsers.Document-
BuilderFactory
system property, through
jre_dir/lib/
jaxp.properties
, through the J2EE Services API and the class spec-
ified in
META-INF/services/javax.xml.parsers.Document-
ch23.fm Page 1135 Friday, April 27, 2001 6:53 AM
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