关于用Schema校验XML的问题？

运行下面这些代码，只要XML文件符合XML规范都能通过，而不会校验是否符合Schema的定义。为什么？


// 在此输入java代码
static final String JAXP_SCHEMA_LANGUAGE =
		"http://java.sun.com/xml/jaxp/properties/schemaLanguage";
		static final String W3C_XML_SCHEMA =
		"http://www.w3.org/2001/XMLSchema"; 
		static final String JAXP_SCHEMA_SOURCE =
		"http://java.sun.com/xml/jaxp/properties/schemaSource";
		static final String MY_SCHEMA_FILE = "cd_catalog_schema.xml";
    
    
    public static void main(String argv[])
    {
        /* Here is some constant used to set properties of the SAX parser. */
		try{
		
				
			DefaultHandler handler = new ParseSchemaXml();
			
			SAXParserFactory factory = SAXParserFactory.newInstance();
			factory.setNamespaceAware(true);
			factory.setValidating(true); 
			SAXParser saxParser = factory.newSAXParser();
			
			saxParser.setProperty(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA); 
			String file = MY_SCHEMA_FILE;
			saxParser.setProperty(JAXP_SCHEMA_SOURCE, new File(file));
			
			File xmlFile = new File("cd_catalog.xml");
			saxParser.parse(xmlFile, handler);
	
	
	        System.exit(0);
		}catch(Exception er){
			System.out.println(er);
		}
    }