This package provides an API for validation of XML documents. Validation is the process of verifying that an XML document is an instance of a specified XML schema. An XML schema defines the content model (also called a grammar or vocabulary) that its instance documents will represent.

There are a number of popular technologies available for creating an XML schema. Some of the most popular include:

Previous versions of JAXP supported validation as a feature of an XML parser, represented by either a {@link javax.xml.parsers.SAXParser} or {@link javax.xml.parsers.DocumentBuilder} instance.

The JAXP validation API decouples the validation of an instance document from the parsing of an XML document. This is advantageous for several reasons, some of which are:

Usage example. The following example demonstrates validating an XML document with the Validation API (for readability, some exception handling is not shown):

            
    // parse an XML document into a DOM tree
    DocumentBuilderFactory parserFactory = DocumentBuilderFactory.newInstance();
    parserFactory.setNamespaceAware(true);
    DocumentBuilder parser = parserFactory.newDocumentBuilder();
    Document document = parser.parse(new File("instance.xml"));

    // create a SchemaFactory capable of understanding WXS schemas
    SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

    // load a WXS schema, represented by a Schema instance
    Source schemaFile = new StreamSource(new File("mySchema.xsd"));
    Schema schema = factory.newSchema(schemaFile);

    // create a Validator instance, which can be used to validate an instance document
    Validator validator = schema.newValidator();

    // validate the DOM tree
    try {
        validator.validate(new DOMSource(document));
    } catch (SAXException e) {
        // instance document is invalid!
    }

The JAXP parsing API has been integrated with the Validation API. Applications may create a {@link javax.xml.validation.Schema} with the validation API and associate it with a {@link javax.xml.parsers.DocumentBuilderFactory} or a {@link javax.xml.parsers.SAXParserFactory} instance by using the {@link javax.xml.parsers.DocumentBuilderFactory#setSchema(Schema)} and {@link javax.xml.parsers.SAXParserFactory#setSchema(Schema)} methods. You should not both set a schema and call setValidating(true) on a parser factory. The former technique will cause parsers to use the new validation API; the latter will cause parsers to use their own internal validation facilities. Turning on both of these options simultaneously will cause either redundant behavior or error conditions.