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https://issues.apache.org/jira/browse/XERCESJ-1772?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Björn Kautler updated XERCESJ-1772:
-----------------------------------
Summary: ClassCastException in SAXParser constructor if Xerces comes from
different thread-context class loaders (was: {{ClassCastException}} in
{{SAXParser}} constructor if Xerces comes from different thread-context class
loaders)
> ClassCastException in SAXParser constructor if Xerces comes from different
> thread-context class loaders
> -------------------------------------------------------------------------------------------------------
>
> Key: XERCESJ-1772
> URL: https://issues.apache.org/jira/browse/XERCESJ-1772
> Project: Xerces2-J
> Issue Type: Bug
> Affects Versions: 2.12.2
> Reporter: Björn Kautler
> Priority: Major
>
> MCVE is following, but the full story is like this:
> - Gradle has Ant integrated on its class loader.
> - Ant in its {{org.apache.tools.ant.util.JAXPUtils.getNSParserFactory}} uses
> {{javax.xml.parsers.SAXParserFactory.newInstance}} to create a
> {{SAXParserFactory}} and remembers it for future usage
> - {{javax.xml.parsers.FactoryFinder.getProviderClass}} uses the TCCL
> (thread-context class loader) to find the {{SAXParserFactory}} to be used
> - Now the {{SAXParserFactory}} that {{JAXPUtils}} remembers is the Xerces
> one from that TCCL that is coming from the build script class path
> - If that {{SAXParserFactory}} now is asked to create a
> {{{}newSAXParser(){}}}, it ultimately calls the
> {{org.apache.xerces.parsers.SAXParser}} constructor from that same class
> loader the factory is coming from
> - This constructor uses
> {{org.apache.xerces.parsers.ObjectFactory.createObject}} to create a new
> {{XMLParserConfiguration}}
> - This method again searches on the current TCCL for the class
> - After an instance was created, it tries to cast it to
> {{XMLParserConfiguration}} from the same class loader as the factory
> If it now happens, that the TCCL changed, for example because you run a
> Gradle build with a different buildscript classpath and thus a different
> class loader containing Xerces you get a {{ClassCastException}} like:
> {code:java}
> class org.apache.xerces.parsers.XIncludeAwareParserConfiguration cannot be
> cast to class org.apache.xerces.xni.parser.XMLParserConfiguration
> (org.apache.xerces.parsers.XIncludeAwareParserConfiguration is in unnamed
> module of loader java.net.URLClassLoader @2280cdac;
> org.apache.xerces.xni.parser.XMLParserConfiguration is in unnamed module of
> loader java.net.URLClassLoader @681a9515)
> {code}
>
> Condensed, you can reproduce this issue with the following lines of code with
> Xerces *not* being on the application classpath:
> {code:java}
> URL[] xercesUrl = {new File("path/to/xercesImpl-2.12.2.jar").toURI().toURL()};
> Thread.currentThread().setContextClassLoader(new URLClassLoader(xercesUrl));
> SAXParserFactory factory = SAXParserFactory.newInstance();
> factory.newSAXParser();
> Thread.currentThread().setContextClassLoader(new URLClassLoader(xercesUrl));
> factory.newSAXParser();{code}
> This results in said {{{}ClassCastException{}}}:
> {code:java}
> Exception in thread "main" java.lang.ClassCastException: class
> org.apache.xerces.parsers.XIncludeAwareParserConfiguration cannot be cast to
> class org.apache.xerces.xni.parser.XMLParserConfiguration
> (org.apache.xerces.parsers.XIncludeAwareParserConfiguration is in unnamed
> module of loader java.net.URLClassLoader @2280cdac;
> org.apache.xerces.xni.parser.XMLParserConfiguration is in unnamed module of
> loader java.net.URLClassLoader @681a9515)
> at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
> at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
> at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.<init>(Unknown
> Source)
> at org.apache.xerces.jaxp.SAXParserImpl.<init>(Unknown Source)
> at org.apache.xerces.jaxp.SAXParserFactoryImpl.newSAXParser(Unknown
> Source)
> at foo.Foo.main(Foo.java:21)
> {code}
>
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