This document contains a list of
Frequently Asked Questions (FAQ) about SAX.
If you have questions about SAX that aren't answered here,
try sending them to the
or to xml-dev.
Last Modified: 28 November 2001
SAX in Java
- How do I learn to use SAX?
Start with the QuickStart link at the left.
Current books covering Java and XML also address SAX2.
- What's a SAX driver, and how do I find
A driver implements the SAX2 XMLReader interface.
It either parses XML directly, or repackages the parser so
you can talk to it using SAX interfaces like
Although you can have the SAX2 interfaces without a driver,
that's not useful;
it'd be like using JDBC without a database.
Most current Java programming environments include SAX2
drivers, along with the interfaces, in the core of their
XML support. That includes servlet environments and JDK 1.4
See the "links" page (in this website's menu) for some parser
distributions you can get if you're temporarily SAX-deprived.
Read the documentation with that distribution; you may need to
know the name of the driver class to make
(See the "quickstart" link for a table of some common
names for SAX drivers.)
- The ContentHandler.characters() callback is
Please read the JavaDoc for this method. A parser may
split text into any number of separate chunks, and some characters
may be reported using ignorableWhitespace() instead
of this callback.
If you want all the text inside an element, you need to collect the
text from the various characters callbacks into a buffer.
Only when you see the endElement event can you be sure that
you have seen all the text, and some of it may really "belong" to
- Why doesn't this SAX parser report the XML
Your parser is correct. The XML and text declarations look like
processing instructions for historical reasons (to avoid breaking
legacy SGML parsers) but they are not processing
instructions. See production 23 in the XML 1.0 Recommendation.
(A SAX2 Extensions 1.1 API will expose the information in
these declarations, although not all parsers will support it.)
- Does SAX support comments/CDATA sections/DOCTYPE
Not in the core API. These kinds of things are
pure lexical details, and are not relevant to most kinds of XML
processing, so it doesn't make sense to put them in the core and
force all implementors to support them.
However, SAX2 is designed to be extensible, and the
LexicalHandler interface is supported by most SAX parsers.
SAX2 parsers are not required to support this handler,
but they are required to report an error if you try to use
handlers they don't support.
- Should I use SAX or DOM?
SAX and DOM are appropriate for different situations. If you're
interested in the advantages and disadvantages of each, see the
link at the left contrasting event based APIs to tree based ones.
If you're interested in socio-political aspects, remember that
SAX was designed without requiring people to drive or fly to any
face-to-face meetings or conferences, so it causes less pollution
than the DOM. It was also designed fully in the open, not
behind closed doors.
- J2SE 1.4 bundles an old version of SAX2.
How do I make SAX2 r2 or later available?
Use the new Endorsed Standards Override Mechanism and copy
sax.jar into the directory specified there.
It'll be something like
for the JDK (or drop the "jre" for the JRE).
Notice that SAX is on the list of standards it's OK
to do this with, right there in alphabetical order.
Using this mechanism should let you redistribute a JRE
with current SAX support.
SAX2 r2 is API compatible with the older SAX2 version
used in the JDK, but it's got better documentation and
some bugfixes. The "SAX2 Extensions 1.1" is where new
features get added.
- Are there SAX2 Conformance Tests?
Some; they're not hosted on this website, since
they're under GPL. See the links page for the xmlconf
project. There are two kinds of tests.
The older tests make sure that SAX2 parsers all do the
Right Thing in terms of parsing XML and reporting errors
or document data. That's essentially an issue of conforming
to the XML 1.0 spec, as its requirements map to SAX2.
There are some newer sax2unit tests covering
SAX2 APIs that don't relate so directly to XML 1.0
Those tests are mostly important as a way that you
can be sure that different SAX2 parsers do the things
described in the API specification.
If they don't, you'd probably end up writing code that
depended on some particular parser, which is just what
SAX is trying to prevent!
SAX in Other Languages
- Where's the formal language-independent
There isn't any, and probably there won't ever be one.
SAX2 in Java is defined by its interfaces and by the
base of running code -- it's more like English Common Law rather than
the heavily codified Civil Code of ISO or W3C specifications. Outside
of Java, SAX is whatever programmers in that language decide it
- Where can I find SAX for a language other than
See the link at the left; there are bindings in
programming languages environments such as Python, Perl,
Pascal, C/C++, and COM.
- I'm having trouble using SAX with COM/Visual Basic/C/C++.
Can you help?
Sorry, no. Microsoft and other organizations and individuals
have released their own software under the name 'SAX', but every one
is slightly different. They are free to use the name, but if you need
help, you'll need to get in touch with the authors directly.
These answers are from David Megginson, who made the
original decision to put SAX into the Public Domain.
- Why is SAX in the Public Domain? Why not LGPL or another
There are two reasons:
A license is a threat -- follow the terms or I'll sue you. I
don't like to make threats because (a) it's rude, and (b) I know that
I could never afford to sue a big company like Sun, Microsoft, Oracle,
or IBM anyway, so it would be undignified to pretend.
Open source licenses cause big headaches for project managers, and
not only because of the recent anti-GPL FUD coming out of Redmond --
including an LGPL or MPL component in a private system may delay a
project for weeks trying to get approval from the legal department and
senior management, at least until the company adapts its culture to an
I respect and use the GPL and other open-source licenses when I
work on other projects, of course, and I appreciate all of the good
that the GPL has done for the world.
- Is the SAX name trademarked?
No: I (David Megginson)
assert no intellectual property rights over it. You can use
the names SAX or Simple API for XML for
anything you want, anywhere you want. That doesn't mean that you can
use my name any way you want.
- May we include part or all of the SAX code and/or
documentation in a book or on a CD?
See the previous answers. SAX is in the Public Domain, so you can
do whatever you want with it. There is no need for
clearance editors at publishing companies to ask for permission.
- Why do so many Canadians work with XML?
It's the only international career open to us if we're not good