Question

I have a simple schema validator method:

// Throws runtime exception if anything goes wrong.
public void validate(String schemaURL, String xml) throws Throwable {
    SAXParserFactory oSAXParserFactory = SAXParserFactory.newInstance();
    SAXParser oSAXParser = null;
    oSAXParserFactory.setNamespaceAware(true);
    SchemaFactory oSchemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
    oSAXParserFactory.setSchema(oSchemaFactory.newSchema(new URL(schemaURL)));
    oSAXParser = oSAXParserFactory.newSAXParser();
    SaxErrorHandler handler = new SaxErrorHandler();
    oSAXParser.parse(new InputSource(new StringReader(xml)),handler);
}

I have a schema hosted at http://myserver.com/schemas/app-config/1.0/app-config-1.0.xsd:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:element name="application">
        <xs:complexType>
            <xs:choice>
                <xs:element ref="info"/>
            </xs:choice>
        </xs:complexType>
    </xs:element>
    <xs:element name="info">
        <xs:complexType>
            <xs:attribute name="name" type="xs:string" use="optional"/>
        </xs:complexType>
    </xs:element>
</xs:schema>

Observe the follow instance of that schema:

<?xml version="1.0" encoding="UTF-8"?>
<application xmlns="http://myserver.com/schemas/app-config/1.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://myserver.com/schemas/app-config/1.0
        http://myserver.com/schemas/app-config/1.0/app-config-1.0.xsd">
    <info
        name="Dummy Application"
    />
</application>

When I pass my validate method the following:

String xmlInstance = readXMLIntoString();
String schemaURL = "http://myserver.com/schemas/app-config/1.0/app-config-1.0.xsd";

validate(schemaURL, xmlInstance);

I get the following error:

org.xml.sax.SAXParseException: cvc-elt.1: Cannot find the declaration of element ‘application’.

• Is something wrong with my schema?
• Is something invalid with my instance?
• Is there a problem with me actually hosting the schema at the URL (although the one used in this example is a mockup, I assure you that the XSD file really is hosted at the URL I’m hitting in the code)?

Why can’t the validator find application declaration?

Answer 1

My original answer stated that schemaLocation was incorrect, which is in fact the case, but for a different reason than I suggested originally. As Kohányi Róbert said, your schema is missing a targetNamespace. Either follow his approach and modify your schema, or replace schemaLocation with noNamespaceSchemaLocation.