How to validate XML against XSD 1.1 in Java?

Unfortunately, neither the JDK bundled version (as of Java 8) nor the latest official version from maven central (2.11.0) contains XSD 1.1 implementation.

You actually need the 2.11.0-xml-schema-1.1-beta version of Xerces to able to run the example in the FAQ you have linked.

You may do one of the following.

1. Download the Xerces2 Java 2.11.0 (XML Schema 1.1) (Beta) binaries from Xerces website and manually add jars to the classpath (or install locally via Maven). Link: http://xerces.apache.org/mirrors.cgi. You need at least the following:

   cupv10k-runtime.jar
   org.eclipse.wst.xml.xpath2.processor_1.1.0.jar
   xercesImpl.jar
   xml-apis.jar
   

2. Use the following unofficial maven dependency.

   <dependency>
       <groupId>org.opengis.cite.xerces</groupId>
       <artifactId>xercesImpl-xsd11</artifactId>
       <version>2.12-beta-r1667115</version>
   </dependency>
   

After searching for a while, this tutorial contains these dependency worked for me:

<dependency>
    <groupId>org.exist-db.thirdparty.xerces</groupId>
    <artifactId>xercesImpl</artifactId>
    <version>2.12.0</version>
    <classifier>xml-schema-1.1</classifier>
</dependency>

<!-- xpath2 and java-cup are needed at runtime
        for xercesImpl Schema 1.1 support -->
<dependency>
    <groupId>org.exist-db.thirdparty.org.eclipse.wst.xml</groupId>
    <artifactId>xpath2</artifactId>
    <version>1.2.0</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>edu.princeton.cup</groupId>
    <artifactId>java-cup</artifactId>
    <version>10k</version>
    <scope>runtime</scope>
</dependency>

Unfortunately, these libraries don't seem to be official. So, use it at your own risk.

I don't think you can use the JAXP service mechanism to search for an XSD 1.1 processor. Load Saxon or Xerces in the normal way, and then enable XSD 1.1 processing. For Saxon this is done using

SchemaFactory.setProperty("http://saxon.sf.net/feature/xsd-version", "1.1")

UPDATE 2021-09-04 In recent Saxon releases, XSD 1.1 is the default, and no special property needs to be set to enable it.

There is a generic XML validator that works with XML Schema v1.1, which uses xercesImpl-xsd11 2.12-beta-r1667115. The validator is available here as a Maven plugin, and here as an embeddable library.