add method

hutool-core/src/test/java/cn/hutool/core/convert/XMLGregorianCalendarConverterTest.java

@@ -0,0 +1,16 @@
+package cn.hutool.core.convert;
+
+import cn.hutool.core.date.DateUtil;
+import org.junit.Assert;
+import org.junit.Test;
+
+import javax.xml.datatype.XMLGregorianCalendar;
+
+public class XMLGregorianCalendarConverterTest {
+
+	@Test
+	public void convertTest(){
+		final XMLGregorianCalendar calendar = Convert.convert(XMLGregorianCalendar.class, DateUtil.parse("2022-01-03 04:00:00"));
+		Assert.assertNotNull(calendar);
+	}
+}