xml-apis imported into msg-rngconverter causes problems when using xml-apis

[steinarb]

I wanted to use xml-apis code in a unit test to verify that the results from msg-rngconverter after converting an XSD and I tried to do this:

    @Test
    void testConvertXsdFilesToRngFiles() throws Exception {
        XsdRngConverterMojo mojo = new XsdRngConverterMojo();
        mojo.xsdInputDirectory = new File(getClass().getClassLoader().getResource("xsd/xhtml1-strict.xsd").getFile()).getParent();
        mojo.rngOutputDirectory = testProperties.getProperty("testOutputDirectory");

        mojo.execute();

        var rngFiles = new File(mojo.rngOutputDirectory).listFiles(rngFileFilter);
        assertThat(rngFiles).hasSize(1);
        assertDoesNotThrow(() -> parseXmlFile(rngFiles[0])); // Verify generated file is XML file
    }

    private Document parseXmlFile(File file) throws Exception {
        var factory = DocumentBuilderFactory.newInstance();
        var builder = factory.newDocumentBuilder();
        return builder.parse(file);
    }

but that got the error:

The package javax.xml.parsers is accessible from more than one module: <unnamed>, java.xml

"mvn depedency:tree" told me that the msg-rngconverter was pulling in xml-apis (which conflicted with the xml-apis in the JDK itself.

So I tried excluding the xml-apis transitive dependency from msg-rngconverter

        <dependency>
            <groupId>net.java.dev.msv</groupId>
            <artifactId>msv-rngconverter</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>xml-apis</groupId>
                    <artifactId>xml-apis</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

and excluding xml-apis worked find for making the unit test compile, but XSD to RNG conversion failed with a ClassNotFoundException

java.lang.Error: com.sun.msv.datatype.xsd.DatatypeFactory$1
	at com.sun.msv.writer.relaxng.PatternWriter.serializeDataType(PatternWriter.java:324)
	at com.sun.msv.writer.relaxng.PatternWriter.onData(PatternWriter.java:248)
	at com.sun.msv.grammar.DataExp.visit(DataExp.java:94)
	at com.sun.msv.writer.relaxng.RELAXNGWriter$SmartPatternWriter.onRef(RELAXNGWriter.java:536)
	at com.sun.msv.grammar.ReferenceExp.visit(ReferenceExp.java:109)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:205)
	at com.sun.msv.writer.relaxng.RELAXNGWriter$SmartPatternWriter.onAttribute(RELAXNGWriter.java:562)
	at com.sun.msv.grammar.AttributeExp.visit(AttributeExp.java:94)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:205)
	at com.sun.msv.writer.relaxng.PatternWriter.onOptional(PatternWriter.java:132)
	at com.sun.msv.writer.relaxng.PatternWriter.onChoice(PatternWriter.java:143)
	at com.sun.msv.grammar.ChoiceExp.visit(ChoiceExp.java:48)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:203)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:202)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:202)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:202)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:202)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:202)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:202)
	at com.sun.msv.writer.relaxng.RELAXNGWriter$SmartPatternWriter.writeElement(RELAXNGWriter.java:577)
	at com.sun.msv.writer.relaxng.RELAXNGWriter$SmartPatternWriter.onElement(RELAXNGWriter.java:546)
	at com.sun.msv.grammar.ElementExp.visit(ElementExp.java:89)
	at com.sun.msv.writer.relaxng.RELAXNGWriter$SmartPatternWriter.onRef(RELAXNGWriter.java:536)
	at com.sun.msv.grammar.ReferenceExp.visit(ReferenceExp.java:109)
	at com.sun.msv.writer.relaxng.PatternWriter.visitBinExp(PatternWriter.java:162)
	at com.sun.msv.writer.relaxng.PatternWriter.onChoice(PatternWriter.java:147)
	at com.sun.msv.grammar.ChoiceExp.visit(ChoiceExp.java:48)
	at com.sun.msv.writer.relaxng.PatternWriter.visitUnary(PatternWriter.java:205)
	at com.sun.msv.writer.relaxng.RELAXNGWriter.writeIsland(RELAXNGWriter.java:359)
	at com.sun.msv.writer.relaxng.RELAXNGWriter.write(RELAXNGWriter.java:335)
	at com.sun.msv.writer.relaxng.RELAXNGWriter.write(RELAXNGWriter.java:187)
	at com.sun.msv.writer.relaxng.Driver.writeGrammar(Driver.java:88)
	at com.sun.msv.writer.relaxng.Driver.main(Driver.java:74)
	at no.priv.bang.maven.plugin.xsdrngconverter.XsdRngConverterMojo.convertXsdFilesToRngFiles(XsdRngConverterMojo.java:66)
	at no.priv.bang.maven.plugin.xsdrngconverter.XsdRngConverterMojo.execute(XsdRngConverterMojo.java:47)
	at no.priv.bang.maven.plugin.xsdrngconverter.XsdRngConverterMojoTest.testConvertXsdFilesToRngFiles(XsdRngConverterMojoTest.java:71)

Scratching my head trying to find a way to do both.

[svanteschubert]

@steinarb, could you provide a test branch on your forked repo, please?
I like to give it a try.

[steinarb]

@svanteschubert I don't have a forked repo.

I am trying to use msv-rngconverter from a maven dependency using the latest version currently on maven central (version 2022.7).

The project where I am using the msv-rngconverter maven dependency, is a maven mojo for converting XSD files to RNG files that I wrote in 2019 and then forgot, until it resurfaced from a dependabot upgrade a couple of days ago:
https://github.com/steinarb/xsd-rng-converter-maven-plugin

I thought "oh! That would be a cool thing to get working!" (I use Relax-NG in my XML editor) and I have since then tried to do an upgrade of basically everything.

In 2019 I was still hanging on to java8, and one of the things that came with java11 was disallowing export of the same package from multiple sources (and I am currently on java21, lazily transitioning to java25). And this is where the included xml-apis is a problem, because it collides with the version of the XML APIs bundled with the JDK.

I have pushed my work in progress on the branch scratch/work-in-progress-upgrading-msv
https://github.com/steinarb/xsd-rng-converter-maven-plugin/tree/scratch/work-in-progress-upgrading-msv

Here is the maven dependency with exclude: https://github.com/steinarb/xsd-rng-converter-maven-plugin/blob/c8a0d05d4af3afc76cdc4663bebc09b6c75601cb/pom.xml#L57

Here is the failing test which uses xml-apis to check that the generated file is actually an XML file (it wasn't earlier, it was a text file containing an error message): https://github.com/steinarb/xsd-rng-converter-maven-plugin/blob/c8a0d05d4af3afc76cdc4663bebc09b6c75601cb/src/test/java/no/priv/bang/maven/plugin/xsdrngconverter/XsdRngConverterMojoTest.java#L65

Since I created this issue I have discovered that removing the exclude on the above maven dependency isn't enough to fix the classnotfoundexception in the failing test.

So this is basically where I 'm currently am in my digging.

I know that the above maven dependency (without exclude) is enough to run in exec-maven-plugin without failing with the classnotfoundexception, because I do so here:
https://github.com/steinarb/liquibase-karaf-feature/blob/8f996adc88722c9dadd0c6354612325a0e580308/liquibase-integration-test/karaf.liquibase.sample/pom.xml#L133
https://github.com/steinarb/liquibase-karaf-feature/blob/8f996adc88722c9dadd0c6354612325a0e580308/liquibase-integration-test/karaf.liquibase.sample/pom.xml#L189

But removing the <exclude> (and the check for that the generated file is actually an XML file) didn't fix the classnotfoundexception in the test in the xsd-rng-converter-maven-plugin project.

[steinarb]

I've been chasing down the "Omitted for conflict" dependencies in "mvn dependency:tree -Dverbose" and all conflicts are now gone. Changes have been pushed to the branch scratch/work-in-progress-upgrading-msv.

And xsdlib which contains the missing type is found twice in "mvn dependency:tree -Dverbose" with the same version in the compile scope (which should cover anything).

Here is the current output of "mvn dependency:tree -Dverbose":

mvn -B dependency:tree -Dverbose
[INFO] Scanning for projects...
[INFO] 
[INFO] ------< no.priv.bang.maven.plugin:xsd-rng-converter-maven-plugin >------
[INFO] Building xsd-rng-converter-maven-plugin Maven Plugin 1.0.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] ----------------------------[ maven-plugin ]----------------------------
[INFO] 
[INFO] --- dependency:3.7.0:tree (default-cli) @ xsd-rng-converter-maven-plugin ---
[INFO] no.priv.bang.maven.plugin:xsd-rng-converter-maven-plugin:maven-plugin:1.0.0-SNAPSHOT
[INFO] +- net.java.dev.msv:msv-rngconverter:jar:2022.7:compile
[INFO] |  +- net.java.dev.msv:xsdlib:jar:2022.7:compile
[INFO] |  |  +- xerces:xercesImpl:jar:2.12.2:compile
[INFO] |  |  \- relaxngDatatype:relaxngDatatype:jar:20020414:compile
[INFO] |  \- net.java.dev.msv:msv-core:jar:2022.7:compile
[INFO] |     +- (net.java.dev.msv:xsdlib:jar:2022.7:compile - omitted for duplicate)
[INFO] |     +- isorelax:isorelax:jar:20030108:compile
[INFO] |     \- (relaxngDatatype:relaxngDatatype:jar:20020414:compile - omitted for duplicate)
[INFO] +- org.apache.maven:maven-plugin-api:jar:3.9.14:compile
[INFO] |  +- org.apache.maven:maven-model:jar:3.9.14:compile
[INFO] |  |  \- (org.codehaus.plexus:plexus-utils:jar:3.6.0:compile - omitted for duplicate)
[INFO] |  +- org.apache.maven:maven-artifact:jar:3.9.14:compile
[INFO] |  |  \- (org.codehaus.plexus:plexus-utils:jar:3.6.0:compile - omitted for duplicate)
[INFO] |  +- org.eclipse.sisu:org.eclipse.sisu.plexus:jar:1.0.0:compile
[INFO] |  |  +- org.codehaus.plexus:plexus-component-annotations:jar:2.2.0:compile
[INFO] |  |  +- (org.codehaus.plexus:plexus-classworlds:jar:2.9.0:compile - omitted for duplicate)
[INFO] |  |  \- (org.codehaus.plexus:plexus-utils:jar:3.6.0:compile - omitted for duplicate)
[INFO] |  +- org.codehaus.plexus:plexus-utils:jar:3.6.0:compile
[INFO] |  \- org.codehaus.plexus:plexus-classworlds:jar:2.9.0:compile
[INFO] +- org.apache.maven.plugin-tools:maven-plugin-annotations:jar:3.15.2:provided
[INFO] +- org.junit.jupiter:junit-jupiter-api:jar:6.0.3:test
[INFO] |  +- org.opentest4j:opentest4j:jar:1.3.0:test
[INFO] |  +- org.junit.platform:junit-platform-commons:jar:6.0.3:test (version managed from 6.0.3)
[INFO] |  |  +- (org.apiguardian:apiguardian-api:jar:1.1.2:test - omitted for duplicate)
[INFO] |  |  \- (org.jspecify:jspecify:jar:1.0.0:test - omitted for duplicate)
[INFO] |  +- org.apiguardian:apiguardian-api:jar:1.1.2:test
[INFO] |  \- org.jspecify:jspecify:jar:1.0.0:test
[INFO] +- org.junit.jupiter:junit-jupiter-engine:jar:6.0.3:test
[INFO] |  +- org.junit.platform:junit-platform-engine:jar:6.0.3:test (version managed from 6.0.3)
[INFO] |  |  +- (org.opentest4j:opentest4j:jar:1.3.0:test - omitted for duplicate)
[INFO] |  |  +- (org.junit.platform:junit-platform-commons:jar:6.0.3:test - version managed from 6.0.3; omitted for duplicate)
[INFO] |  |  +- (org.apiguardian:apiguardian-api:jar:1.1.2:test - omitted for duplicate)
[INFO] |  |  \- (org.jspecify:jspecify:jar:1.0.0:test - omitted for duplicate)
[INFO] |  +- (org.junit.jupiter:junit-jupiter-api:jar:6.0.3:test - version managed from 6.0.3; omitted for duplicate)
[INFO] |  +- (org.apiguardian:apiguardian-api:jar:1.1.2:test - omitted for duplicate)
[INFO] |  \- (org.jspecify:jspecify:jar:1.0.0:test - omitted for duplicate)
[INFO] \- org.assertj:assertj-core:jar:3.27.7:test
[INFO]    \- net.bytebuddy:byte-buddy:jar:1.18.3:test
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.149 s
[INFO] Finished at: 2026-03-31T14:01:25+02:00
[INFO] ------------------------------------------------------------------------

[svanteschubert]

I quickly took a look at your current changes on your branch:
steinarb/xsd-rng-converter-maven-plugin@master...scratch/work-in-progress-upgrading-msv

• We should be generally careful in changing the APIs, e.g. removing a "public", the method signature
• Currently, the project claims to be built with JDK 1.8; be careful with upgrading Maven dependencies. But we could upgrade to JDK 11.

Please note, I started to quickly try a JDK 11 build and removed the xml-api from the msv-core, as after JDK 9, the modularity is active.

Does this help?

See https://github.com/xmlark/msv/tree/jdk11

[steinarb]

@svanteschubert Thanks!

No luck unfortunately! I get the same missing-at-runtime message from the xsdlib DataFactory anonymous inner class (I have a feeling the classnotfoundexception isn't caused by the xml-apis dependency

"mvn clean install" results here (with a bookmark on the failing test stack trace, the other failing test is failing the way it is supposed to currently, I haven't gotten around to fixing it yet: https://gist.github.com/steinarb/c222c911ebebe908ea9deb16ca2897f6#file-gistfile1-txt-L101
"mvn dependency:tree -verbose results here (Note that there is still a transitive dependency on xml-apis, but it doesn't cause a build failure): https://gist.github.com/steinarb/8186b3e9e80f229d9764b08045714144

My platform:

• Debian 13.4 "trixie", amd64
• openjdk version "21.0.10" 2026-01-20 (build 21.0.10+7-Debian-1deb13u1)
• Apache Maven 3.9.10 (5f519b97e944483d878815739f519b2eade0a91d)

What I did to test:

1. Did git pull -p on main in an existing msv clone, followed by mvn clean install
2. Changed the msv-rngconverter dependency in my project: removed the exclusions and set the version to 2202.8-SNAPSHOT

       <dependency>
           <groupId>net.java.dev.msv</groupId>
           <artifactId>msv-rngconverter</artifactId>
           <version>2022.8-SNAPSHOT</version>
       </dependency>
   

3. Built my project with mvn clean install

Note! I did rm -rf ~/.m2/repositories earlier today, without that having any effect on the classnotfoundexception

Also created a gist with the results of "mvn -X clean install" in xsd-rng-converter-maven-plugin: https://gist.github.com/steinarb/b0421582c2672fa0261879b16cfa48b7

[steinarb]

@svanteschubert The xml-apis problem is a real one, post java 9 or java 11 and should be fixed.

But it will not fix the error in my test, which I think is a classloader issue.

I have stopped at the exception throwing line in the debugger, and this is what I see

1. The debugger is stopped here:

   msv/msv/src/main/java/com/sun/msv/writer/relaxng/PatternWriter.java

   Line 324 in dc2a642

   throw new Error(x.getClass().getName());

2. x says it is of type "DatatypeFactory$1"
3. x is assigned from the method argument "XSDDataType dt" here:

   msv/msv/src/main/java/com/sun/msv/writer/relaxng/PatternWriter.java

   Line 277 in dc2a642

   XSDatatype x = dt;

4. dt is of type FinalComponent according to the debugger
5. Which means that dt should have enthered the codeblock beneath this if statement

   msv/msv/src/main/java/com/sun/msv/writer/relaxng/PatternWriter.java

   Line 280 in dc2a642

   if (x instanceof FinalComponent) {

6. The fact that it doesn't enter the if test tells me that there is a ClassLoader issue going on here (even though I can't see exactly what that ClassLoader issue is, because this is a plain java project...?)