ADDITIONAL SYSTEM INFORMATION :
Java 17.0.7

A DESCRIPTION OF THE PROBLEM :
If I create a xsd validator I'm unable to get the results in english.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
- set `user.language` to `de`
- create a validator
- set language of this validator to "en"


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
error message is in english
ACTUAL -
error message is in german (user.language)

---------- BEGIN SOURCE ----------
package de.quick.common.xml;

import java.io.ByteArrayInputStream;
import java.nio.charset.StandardCharsets;
import java.util.Locale;
import javax.xml.XMLConstants;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;

import org.junit.Assert;
import org.junit.Test;
import org.xml.sax.SAXException;

public class XsdValidatorBugTest {

  private String xsd = """
      <?xml version="1.0" encoding="ISO-8859-1"?>
      <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
                 targetNamespace="http://abc"
                 elementFormDefault="qualified" attributeFormDefault="unqualified" version="V1.0.0">
            
          <xs:element name="Kug">
              <xs:complexType>
                  <xs:sequence>
                      <xs:element name="PG">
                        <xs:simpleType>
                          <xs:restriction base="xs:string">
                              <xs:minLength value="1"/>
                              <xs:pattern value="[A-Z]+"/>
                          </xs:restriction>
                        </xs:simpleType>
                      </xs:element>
                  </xs:sequence>
              </xs:complexType>
          </xs:element>
      </xs:schema>""";

  private String xml = """
      <?xml version="1.0" encoding="ISO-8859-1"?>
      <Kug xmlns="http://abc">
          <PG>AB1</PG>
      </Kug>""";


  @Test
  public void validator_has_wrong_language() throws Exception {
    // make sure user.language is "de"
    // if it fails use "-Duser.language=es" as parameter
    Assert.assertEquals("de", System.getProperty("user.language"));

    // create validator
    Validator xsdValidator = createXsdValidator();


    // ******************************************************************************************************************
    // test #1 ... set language to french
    xsdValidator.setProperty("http://apache.org/xml/properties/locale", new Locale("fr"));


    StreamSource source1 = new StreamSource(new ByteArrayInputStream(xml.getBytes(StandardCharsets.ISO_8859_1)));
    try {
      xsdValidator.validate(source1);
      Assert.fail("not expected to reach here");
    } catch (SAXException e) {
      Assert.assertEquals("cvc-pattern-valid : La valeur 'AB1' n'est pas un facet valide par rapport au modxE8le '[A-Z]+' pour le type '#AnonType_PGKug'.", e.getMessage());
    }


    // ******************************************************************************************************************
    // test #2 ... now setting language to english
    xsdValidator.setProperty("http://apache.org/xml/properties/locale", new Locale("en"));


    StreamSource source2 = new StreamSource(new ByteArrayInputStream(xml.getBytes(StandardCharsets.ISO_8859_1)));
    try {
      xsdValidator.validate(source2);
      Assert.fail("not expected to reach here");
    } catch (SAXException e) {
      Assert.assertEquals("cvc-pattern-valid: Value 'AB1' is not facet-valid with respect to pattern '[A-Z]+' for type '#AnonType_PGKug'.", e.getMessage());
    }
  }


  private Validator createXsdValidator() throws Exception {
    SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
    StreamSource xsdSource = new StreamSource(new ByteArrayInputStream(xsd.getBytes(StandardCharsets.ISO_8859_1)));
    Schema schema = schemaFactory.newSchema(xsdSource);
    return schema.newValidator();
  }
}

---------- END SOURCE ----------

FREQUENCY : always