Where do I go to learn about XSLT?
The definitive sources are the W3C XSLT and XPath recommendations: W3C Recommendation 16 November 1999 XSL Transformations (XSLT) Version 1.0 and XML Path Language (XPath) Version 1.0.
For a brief listing of tutorials, discussion forums, and other materials, see Getting up to speed with XSLT.
Where can I ask a question?
The Apache Software Foundation has information on how you can subscribe to the mailing lists.
You can post messages to the lists by sending mail to:
Again, please review the archives before posting a new question.
What is Xerces-C++ and why do I need it?
Xerces-C++ is a validating XML parser written in a portable subset of C++. Xerces-C++ makes it easy to give your application the ability to read and write XML data. Like Xalan-C++, Xerces-C++ is available from the Apache XML site: http://xerces.apache.org.
Which version of Xerces-C++ should I be using?
The Xalan-C++ release notes includes information about the Xerces-C++ release with which the Xalan-C++ release has been coordinated and tested. See the release history.
Should I be using the Xerces DOM or Xalan DOM?
The Xalan DOM implementation is highly optimised for transformations. However, whilst you can build documents in the Xalan DOM, subsequent modification will not work. The Xalan DOM is designed to be either an input or an output from a transformation, not as a general DOM implementation.
So in cases where you want to simply transform documents using Xalan, using the internal DOM implementation is the best approach.
In cases where you want to modify the DOM document on the fly, you should use the Xerces DOM as the base document. You can wrap the Xerces DOM in a wrapper (see Passing in a Xerces DOM) to then use as an input to a Xalan transformation. Alternatively you can output the result of a transformation to a Xerces DOM document (see Working with DOM input and output). In either case, the Xerces document can be freely modified. However, after you modify the document, you need to re-build the wrapper so that any changes are replicated in the Xalan wrappers.
I have encountered problem executing the Xalan-C++ sample applications
after rebuilding them under Win32 Environment (Windows NT 4.0, SP3).
When I tried to execute the sample, I receive the error message
Debug Assertion Failed! … Expression: _BLOCK_TYPE_IS_VALID(pHead->nBlockUse).
You may be mixing debug and release versions of executables and libraries. In other words, if you are compiling the sample for debug, then you should link with the debug version of the Xalan-C++ and Xerces-C++ libraries and run with the debug version of the dynamic link libraries.
You must also make sure your application is linking with the “Debug Multithreaded DLL” run-time library or the “Multithreaded DLL” run-time library. To check this setting do the following in Visual C++:
Once you have changed this setting, you must rebuild your project.
Note: This FAQ entry is largely historical. While mixing Release and Debug builds and different runtimes is still inadvisable, the CMake build system should link the correct versions of the libraries and prevent this happening by accident.
What do I need to rebuild Xalan-C++ on Windows?
What do I need to rebuild Xalan-C++ on UNIX?
What is ICU and why do I need it?
The International Components for Unicode (ICU) is a C and C++ library that provides robust and full-featured Unicode support on a wide variety of platforms. Xalan-C++ uses the ICU to extend support for encoding, number formatting, and sorting.
Xalan should work with any release of ICU from the past decade.
For more details see Using the International Components for Unicode (ICU).
I am getting a tar checksum error on Solaris. What’s the problem?
The Solaris tar utility you are using does not properly handle files with long pathnames. You must use GNU tar (gtar), which handles arbitrarily long pathnames and is freely available on every platform on which Xalan-C++ is supported. If you don’t already have GNU tar installed on your system, you can obtain it from the Free Software Foundation http://www.gnu.org/software/tar/tar.html. For additional background information on this problem, see the online manual GNU tar and POSIX tar for the utility.
Is it possible to run Xalan-C++ from an Apache server?
A simple Apache module called ApacheModuleXSLT is provided as a sample. It demonstrates how to integrate Xalan-C++ with Apache.
Is Xalan-C++ thread-safe?
are not thread-safe; each thread should use its own instance.
In order to support very efficient use in multi-threaded applications, Xalan-C++ is designed to avoid synchronization as much as possible. Each thread of execution is required to have its own set of “support” objects that contain the state of the transformation. Accordingly, no synchronization is required when multiple threads are executing.
Parsed (“compiled”) stylesheets (see
Performing a series of transformations)
and parsed source documents may be freely shared by multiple threads of
execution without worrying about providing synchronized access to them.
The only exception to this rule: You use
to parse a document after calling
In this case, the document cannot be shared by multiple threads of
execution. For reasons of performance, we do not recommend the use of
XercesParserLiaison, so this should not be an issue for most
All other objects in Xalan-C++ are not thread-safe. Each thread must have its own instance of each object.
See the ThreadSafe sample program for more information.
What can I do to speed up transformations?
To maximize performance, here are some suggestions for you to keep in mind as you set up your applications:
//(descendant axes) patterns near the root of a large document.
xsl:keyelements and the
key()function as an efficient way to retrieve node sets.
xsl:for-eachis fast because it does not require pattern matching.
xsl:sortprevents incremental processing.
<xsl:variable name="fooElem" select="foo"/>is usually faster than
Can I validate an XSL stylesheet?
An XSL stylesheet is an XML document, so it can have a
DOCTYPE and be
subject to validation, but you probably will have to write a custom DTD
for the purpose.
The XSLT Recommendation includes a DTD Fragment for XSL Stylesheets with some indications of what you need to do to create a complete DTD for a given stylesheet. Keep in mind that stylesheets can include literal result elements and produce output that is not valid XML.
You can use the
xsl:stylesheet doctype defined in
for stylesheets that generate HTML.
It means that an attempt was made to add a node to a DOM that would create an invalid structure. For example, text nodes are not allowed as children of the document node.
This is a common error when attempting to transform to DOM. Source documents and stylesheets that might produce valid serialized XML might not produce a valid DOM. The usual suspect is text nodes being generated before the document element is generated.
If you think you have seen this error because of a bug in Xalan-C++’s source tree implementation, please post a bug report on Jira, and attach a minimal source document and stylesheet that produce the problem to the bug report.
Who do I submit patches to?
Your contributions are much appreciated! You can e-mail your patches to the Xalan Development Mailing List or raise an issue on the Jira issue tracking system.
The Xalan projects use Jira as the issue tracking system. Any significant bug or feature request is posted to this system. You must subscribe to the system in order to submit patches and raise issues.
Issues posted to the project on Jira at
XALANC are automatically
posted to the Xalan Development Mailing List.
Our mailing lists are moderated. You should subscribe to the mailing list in order to post a message, otherwise message delivery requires manual intervention or may be dropped.
How do I output a transformation to a DOM, a file, an in-memory buffer, or as input to another transformation?
Since the C++ language can automatically construct an
from any of its constructor’s argument types, you usually don’t need to
create one explicitly.
Output to a file:
XSLTResultTarget. Or, use an instance of
std::ofstream. The command line executables, and many of the sample applications use file names, so take a look through the source code for more information.
Output to an in-memory buffer:
std::ostringstreamto create an XSLTResultTarget. See the StreamTransform sample for more information.
Input to another transformation:
FormatterToSourceTreeis probably the best for efficiency reasons. See the source code for the
TestXSLTcommand line program for more information.
Why won’t XSLTInputSource work with
std::istrstream on Sun Solaris
using Forte/Sun Workshop compiler?
There is a bug in Sun’s C++ standard library implementation for the Forte/Workshop compiler. The short answer is that you need to get a patch.
The issue is resolved if you use the SunStudio platform for your code development. The Solaris SunStudio is now available from Oracle.
No, you aren’t going crazy. Xalan’s default source tree is read-only for efficiency. If you need a DOM that supports modifications, use the Xerces DOM instead. See the TransformToXercesDOM sample for more information.
XalanTransformer outputs errors to the console. How do I, for example, output error to a file?
std::cerrfrom the command line.
XalanTranformer::setWarningStreamwith a different
XalanTransformerProblemListenerwith a different output stream and call
ProblemListenertype and do custom handling of errors (you still then need to tell
XalanTransformerinstances to use your
In most cases you probably want to do one of the first two.
How do I programmatically get the file name, line number, and column number for an error in an XML file?
Create a custom
ErrorHandler (a Xerces-C++ class) and call
before parsing any sources.
How do I make a
char* out of
See the static method
or the functions
However, you should be very careful when transcoding Unicode characters
to the local code page, because not all Unicode characters can be
Is there a table of error codes somewhere? How about a summary of what methods throw which exceptions?
There isn’t, but we’re working on it.
The Xalan extension functions (
xalan:node-set(), etc.) don’t work for
Did you declare the namespace on the
xsl:transform element? It should look like this:
<xsl:stylesheet version="1.0" xmlns:xalan="http://xml.apache.org/xalan"> …rest of stylesheet
If you did and you still have problems, you might want to ask the mailing list.
Why does Xalan emit a warning when using the XSLT function
Did you build with ICU support? See Using the International Components for Unicode (ICU).
Is there a Perl wrapper for Xalan-C++?
There is no Apache Perl wrapper, however Edwin Pratomo has written a wrapper for Xalan-C++ version 1.4 that can be found on CPAN.
Why can’t I find the *LocalMsgIndex.hpp file?*
The LocalMsgIndex.hpp file is not shipped with the source distributions because this file is generated during the build process, customized for the locale and message set you are using.
The LocalMsgIndex.hpp file is a member of the include/xalanc/PlatformSupport directory.