Module java.xml

Package javax.xml.validation

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 ones include:

While JAXP supports validation as a feature of an XML parser, represented by either a SAXParser or DocumentBuilder instance, the Validation API is preferred.

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:

  • Support for additional schema langauges. The JAXP parser implementations support only a subset of the available XML schema languages. The Validation API provides a standard mechanism through which applications may take of advantage of specialization validation libraries which support additional schema languages.
  • Easy runtime coupling of an XML instance and schema. Specifying the location of a schema to use for validation with JAXP parsers can be confusing. The Validation API makes this process simple (see example below).

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
     DocumentBuilder parser = DocumentBuilderFactory.newInstance().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 Schema with the validation API and associate it with a DocumentBuilderFactory or a SAXParserFactory instance by using the DocumentBuilderFactory.setSchema(Schema) and 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.