Configuring Parser

| Questions |
| Validation and infoset augmentation Default Parser Configuration Validation Features Validation against a specific schema language
| Answers |
| What's the result of having a DTD validator or XML Schema validator in the pipeline? |
| If a validator is included in the pipeline, the assessment is done, whether the validation feature is set to true or false. The validation feature only enables the validation constraint error reporting and it does not control the infoset augmentation: if a validator is included in the pipeline the parser will augment the infoset according to the grammar specified for the instance document.
| What validation behavior do I expect from the default parser configuration? |
| The default configuration (org.apache.xerces.parsers.XIncludeAwareParserConfiguration) includes the DTD validator and the document scanner (which are both capable of namespace binding). Thus, the validation feature will enable validation against a DTD only. To allow validation against XML Schemas you must turn on the validation feature and the schema feature, and XML Schema Validator will be inserted in the pipeline. if you've created your own configuration which does not extend XIncludeAwareParserConfiguration (or another suitable configuration included with the parser), you must make sure that your configuration inserts all needed validators in the pipeline.
| What happens if I set both validation and schema validation features on? |
| If both validators are present in the pipeline (this is the default behavior), then if the instance document has only a DTD grammar (DOCTYPE before the root element), then only DTD validation errors are reported; if the instance document has only XML Schema grammars, then only XML Schema validation errors are reported if the instance document has both DTD and XML Schema grammars, validation errors for both DTD and XML Schema are reported; if no grammar can be found for the instance document, the last validator in the pipeline will report validation errors. An application may choose to create a configuration that does not have a DTD validator but has an XML Schema validator. This will turn Xerces into a non-compliant processor according to XML 1.0 and XML Schema specifications, thus the validation/augmentation outcome is undefined.
| How can I tell the parser to validate against XML Schema and not to report DTD validation errors? |
| Using JAXP you can instruct the parser to validate against XML Schema only. The JAXP 1.4 Validation API allows you to build an in-memory representation of an XML Schema which you can then set on a parser factory. Parsers created from the factory will validate documents using the schema object you specified. By doing the following you can configure a SAX parser or DocumentBuilder to validate against XML Schema only:
    import javax.xml.XMLConstants;
    import javax.xml.parsers.DocumentBuilder;
    import javax.xml.parsers.DocumentBuilderFactory;
    import javax.xml.parsers.SAXParser;
    import javax.xml.parsers.SAXParserFactory;
    import javax.xml.transform.stream.StreamSource;
    import javax.xml.validation.Schema;
    import javax.xml.validation.SchemaFactory;

    ...

    StreamSource[] sources = /* created by your application */;

    SchemaFactory factory =
        SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
    Schema schema = factory.newSchema(sources);

    /** Setup SAX parser for schema validation. */
    SAXParserFactory spf = SAXParserFactory.newInstance();
    spf.setNamespaceAware(true);
    spf.setSchema(schema);
    SAXParser parser = spf.newSAXParser();

    /** Setup DocumentBuilder for schema validation. */
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    dbf.setNamespaceAware(true);
    dbf.setSchema(schema);
    DocumentBuilder db = dbf.newDocumentBuilder();

    ...
Changing the value of the schema language parameter passed to `SchemaFactory.newInstance()` to `http://www.w3.org/XML/XMLSchema/v1.1` will create a processor which supports XML Schema 1.1.
    import javax.xml.transform.stream.StreamSource;
    import javax.xml.validation.Schema;
    import javax.xml.validation.SchemaFactory;

    ...

    StreamSource[] sources = /* created by your application */;

    SchemaFactory factory =
        SchemaFactory.newInstance("http://www.w3.org/XML/XMLSchema/v1.1");
    Schema schema = factory.newSchema(sources);

    ...
Another option is to use the JAXP schema language property defined by JAXP 1.2. If the schema language property has been set to `http://www.w3.org/2001/XMLSchema` and the parser has been configured to validate then your documents will be validated against XML Schema only, even if they have a DTD. By doing the following you can configure a SAX parser to validate against XML Schema only:
    import javax.xml.parsers.SAXParser;
    import javax.xml.parsers.SAXParserFactory;

    ...
    SAXParserFactory spf = SAXParserFactory.newInstance();
    spf.setValidating(true);
    spf.setNamespaceAware(true);
    SAXParser parser = spf.newSAXParser();
    parser.setProperty(
        "http://java.sun.com/xml/jaxp/properties/schemaLanguage",
        "http://www.w3.org/2001/XMLSchema");
    ...
For a DocumentBuilder this can be accomplished by doing the following:
    import javax.xml.parsers.DocumentBuilder;
    import javax.xml.parsers.DocumentBuilderFactory;

    ...
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    dbf.setNamespaceAware(true);
    dbf.setValidating(true);
    dbf.setAttribute(
        "http://java.sun.com/xml/jaxp/properties/schemaLanguage",
        "http://www.w3.org/2001/XMLSchema");
    DocumentBuilder docBuilder = dbf.newDocumentBuilder();
    ...

Copyright © 1999-2010 The Apache Software Foundation. All Rights Reserved.