private void validateXML(DOMSource source) throws Exception {
    URL schemaFile = new URL("http://www.csc.liv.ac.uk/~valli/modules.xsd");
    SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI);
    Schema schema = schemaFactory.newSchema(schemaFile);

    Validator validator = schema.newValidator();
    DOMResult result = new DOMResult();
    try {
        validator.validate(source, result); 
        System.out.println("is valid");
    } catch (SAXException e) {
        System.out.println("not valid because " + e.getLocalizedMessage());
    }
}

但是，这将返回一条错误消息：线程“
main”中的异常java.lang.IllegalArgumentException：无法加载实现由http://www.w3.org/2001/XMLSchema
-instance 指定的模式语言的SchemaFactory。

这是我的代码还是实际的xsd文件有问题？