JDK XSTC transformer (originally based on Xalan) already supports StAXResult.
Through SIP, and javax.xml.datatype.FactoryFinder, putting Xalan on the classpath actually breaks JDK JAXP Transformer support: Xalan Transformer factory masks JDK Transformer factory.
Having support for StAXSource/StAXResult in Xalan would restore JDK JAXP capabilities.
- Please note that System Properties are NOT an option for web apps.
- Please note that explicitly accessing a JDK internal class is also tricky.
Voting for this feature.