Frequently asked questions

Where do I go to learn about XSLT

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.

Asking questions about Xalan-C++

Where can I ask a question?

For specific questions on Xalan-C++, see list archives: xalan-c-users and xalan-dev. You must subscribe to these Apache mailing lists before posting your questions.

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++?

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?

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?

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.

Problems with samples in Windows

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++:

  1. Select “Settings” from the “Project” menu.
  2. Click the “C/C++” tab.
  3. In the Category drop-down list, select “Code Generation”.
  4. In the “Use run-time library” drop-down list, select “Multithreaded DLL” for the “Win32 Release” configuration, or select “Debug Multithreaded DLL” for the “Win32 Debug” configuration.

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.

Building on Windows

What do I need to rebuild Xalan-C++ on Windows?

For more details, see Downloading Xalan-C++ and Building Xalan-C++.

Building on UNIX

What do I need to rebuild Xalan-C++ on UNIX?

For more details, see Downloading Xalan-C++ and Building Xalan-C++.

What is ICU

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).

A tar checksum error on Solaris

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.

Xalan-C++ in Apache

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?

Is Xalan-C++ thread-safe?

Instances of XalanTransformer 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 XercesParserLiaison to parse a document after calling XercesParserLiaison::setBuildBridgeNodes(false) or XercesParserLiaison::setThreadSafe(false). 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 applications.

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?

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:

Stylesheet validation

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 xsl-html40s.dtd for stylesheets that generate HTML.

What does the XalanDOMException HIERARCHY_REQUEST_ERR mean?

What does the XalanDOMException HIERARCHY_REQUEST_ERR mean?

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.

Submitting Patches

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.

Transformation Output Methods

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 XSLTResultTarget from any of its constructor’s argument types, you usually don’t need to create one explicitly.

The output parameter of XalanTransformer::transform() is an XSLTResultTarget which has many constructors.

Output to a file:

Output to an in-memory buffer:

Input to another transformation:

Problems Using Sun’s Forte/Workshop Compiler with code containing std::istrstream

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.

Modifying an instance of XalanDocument

My transformation outputs to a XalanDocument (actually XalanSourceTreeDocument underneath) but W3C DOM functions like DOMElement::setAttribute don’t work! Am I going crazy or what?

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.

Changing Where Error Output is Sent

XalanTransformer outputs errors to the console. How do I, for example, output error to a file?

By default, XalanTransformer creates a XalanTransformerProblemListener (a subclass of ProblemListener) that writes output to std::cerr. To change this you can:

In most cases you probably want to do one of the first two.

Programmatic Error Information

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 XalanTransformer::setErrorHandler before parsing any sources.

String Transcoding

How do I make a char* out of XalanDOMString (or vice-versa)?

See the static method XalanDOMString::transcode, or the functions TranscodeToLocalCodePage. However, you should be very careful when transcoding Unicode characters to the local code page, because not all Unicode characters can be represented.

Error Code/Exception Summary

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.

Extension Functions

The Xalan extension functions (xalan:node-set(), etc.) don’t work for me. Help!

Did you declare the namespace on the xsl:stylesheet or 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.

Using format-number and ICU

Why does Xalan emit a warning when using the XSLT function format-number()?

Did you build with ICU support? See Using the International Components for Unicode (ICU).

Perl wrapper for Xalan-C++?

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.

Missing LocalMsgIndex.hpp file

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.