4 Validating XML Documents

4.1The Validator Class

The Validator class encapsulates XMLUnit’s validation support. It will use the SAXParser configured in XMLUnit (see Section 2.4.1).

The piece of XML to validate is specified in the constructor. The constructors using more than a single argument are only relevant if you want to validate against a DTD and need to provide the location of the DTD itself - for details see the next section.

By default, Validator will validate against a DTD, but it is possible to validate against a (or multiple) Schema(s) as well. Schema validation requires an XML parser that supports it, of course.

4.1.1DTD Validation

Validating against a DTD is straight forward if the piece of XML contains a DOCTYPE declaration with a SYSTEM identifier that can be resolved at validation time. Simply create a Validator object using one of the single argument constructors.

Example 4.1 Validating Against the DTD Defined in DOCTYPE

InputSource is = new InputSource(new FileInputStream(myXmlDocument));

Validator v = new Validator(is);

boolean isValid = v.isValid();

If the piece of XML doesn’t contain any DOCTYPE declaration at all or it contains a DOCTYPE but you want to validate against a different DTD, you’d use one of the three argument versions of Validator’s constructors. In this case the publicId argument becomes the PUBLIC and systemId the SYSTEM identifier of the DOCTYPE that is implicitly added to the piece of XML. Any existing DOCTYPE will be removed. The systemId should be a URL that can be resolved by your parser.

Example 4.2 Validating a Piece of XML that doesn’t Contain a DOCTYPE

InputSource is = new InputSource(new FileInputStream(myXmlDocument));

Validator v = new Validator(is,

(new File(myDTD)).toURI().toURL().toString(), myPublicId);

boolean isValid = v.isValid();

If the piece of XML already has the correct DOCTYPE declaration but the declaration either doesn’t specify a SYSTEM identifier at all or you want the SYSTEM identifier to resolve to a different location you have two options:

• Use one of the two argument constructors and specify the alternative URL as systemId.

Example 4.3 Validating Against a Local DTD

InputSource is = new InputSource(new FileInputStream(myXmlDocument));

Validator v = new Validator(is,

(new File(myDTD)).toURI().toURL().toString()); boolean isValid = v.isValid();

•Use a custom EntityResolver via XMLUnit.setControlEntityResolver together with one of the single argument constructor overloads of Validator.

This approach would allow you to use an OASIS catalog10 in conjunction with the Apache XML Resolver library11 to resolve the DTD location as well as the location of any other entity in your piece of XML, for example.

10http://www.oasis-open.org/committees/download.php/14809/xml-catalogs.html

11http://xml.apache.org/commons/components/resolver/index.html