Multiple transitive XSLT includes handled differently by Saxon in Camel vs Java - apache-camel

Question

Using Saxon 9.5.1-4 as my XSLT transformation engine in a JUnit test, I see the following warning:
Warning: Stylesheet module file:/C:/svn/prime/code/trunk/xslt/target/main/classes/xsl/common/to-common-result.xsl is included or imported more than once. This is permitted, but may lead to errors or unexpected behavior
But when this runs under Apache-Camel 2.13.1, it fails after the warning.
15:11:29,714 WARN [org.apache.camel.builder.xml.XsltErrorListener] (ServerService Thread Pool -- 90) Stylesheet module ../common/to-common-result.xsl is included or imported more than once. This is permitted, but may lead to errors or unexpected behavior
15:11:29,714 ERROR [org.apache.camel.builder.xml.XsltErrorListener] (ServerService Thread Pool -- 90) A stylesheet cannot import itself; SystemID: ; Line#: 11; Column#: 53: net.sf.saxon.trans.XPathException: A stylesheet cannot import itself
at net.sf.saxon.style.StyleElement.compileError(StyleElement.java:1961) [Saxon-HE-9.5.1-4.jar:]
at net.sf.saxon.style.XSLGeneralIncorporate.checkForRecursion(XSLGeneralIncorporate.java:234) [Saxon-HE-9.5.1-4.jar:]
at net.sf.saxon.style.XSLGeneralIncorporate.getIncludedStylesheet(XSLGeneralIncorporate.java:123) [Saxon-HE-9.5.1-4.jar:]
at net.sf.saxon.style.StylesheetModule.spliceIncludes(StylesheetModule.java:143) [Saxon-HE-9.5.1-4.jar:]
at net.sf.saxon.style.XSLGeneralIncorporate.getIncludedStylesheet(XSLGeneralIncorporate.java:210) [Saxon-HE-9.5.1-4.jar:]
What might account for the difference?
The import structure looks like this:
A imports B, C;
B imports D, E, F;
C imports G;
F imports G;
G is to-common-result.xsl in this example

Answer 1

I think the clue is that in the error message
15:11:29,714 ERROR [org.apache.camel.builder.xml.XsltErrorListener] (ServerService Thread Pool -- 90) A stylesheet cannot import itself; SystemID: ; Line#: 11; Column#: 53: net.sf.saxon.trans.XPathException: A stylesheet cannot import itself
the SystemId is blank. This suggests that the stylesheet is somehow being compiled without knowledge of the correct URI for each module, which means that Saxon is liable to think that a module is importing itself, because both have a blank URI.
So you need to look at how Apache-Camel is invoking the transformation, and why it hasn't supplied Saxon with a correct base URI for the stylesheet.