Run the following java program:

import java.io.StringReader;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.namespace.QName;
import javax.xml.transform.stream.StreamSource;

public class TestJAXB {

    public static void main(String[] args) throws Exception {
        // marshal
        int[] x = new int[]{1,5,2,3,4};
        JAXBElement<int[]> xe = new JAXBElement<int[]>(new QName("", "root"), int[].class, JAXBElement.GlobalScope.class, x);
        Marshaller m = JAXBContext.newInstance(int[].class).createMarshaller();
        m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,true);
        m.marshal(xe,System.out);
        
        // unmarshal
        Unmarshaller u = JAXBContext.newInstance(int[].class).createUnmarshaller();
        JAXBElement e = u.unmarshal(new StreamSource(new StringReader(
                "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n" +
                "<root>\n" +
                " <item>1</item>\n" +
                " <item>5</item>\n" +
                " <item>2</item>\n" +
                " <item>3</item>\n" +
                " <item>4</item>\n" +
                "</root>\n")), int[].class);
    }
}

Exception in thread "main" javax.xml.bind.JAXBException: Package java.lang with JAXB class [I defined in a module java.base must be open to at least java.xml.bind module.
at java.xml.bind@9/javax.xml.bind.ModuleUtil.delegateAddOpensToImplModule(ModuleUtil.java:148)
at java.xml.bind@9/javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:285)
at java.xml.bind@9/javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:270)
at java.xml.bind@9/javax.xml.bind.ContextFinder.find(ContextFinder.java:407)
at java.xml.bind@9/javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:706)
at java.xml.bind@9/javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:647)
at TestJAXB.main(TestJAXB.java:16)


Please note, the exception is thrown in JAXBContext.newInstance(int[].class), other code is just to show a whole example.