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<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
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DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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This code is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License version 2 only, as
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published by the Free Software Foundation. Oracle designates this
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particular file as subject to the "Classpath" exception as provided
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by Oracle in the LICENSE file that accompanied this code.
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This code is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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version 2 for more details (a copy is included in the LICENSE file that
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accompanied this code).
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You should have received a copy of the GNU General Public License version
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2 along with this work; if not, write to the Free Software Foundation,
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Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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or visit www.oracle.com if you need additional information or have any
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questions.
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-->
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>javax.xml.validation</title>
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<meta name="CVS"
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content="$Id: package.html,v 1.2 2005/06/10 03:50:43 jeffsuttor Exp $" />
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<meta name="AUTHOR"
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content="Jeff.Suttor@Sun.com" />
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</head>
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<body>
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<p>
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This package provides an API for validation of XML documents. <em>Validation</em> is the process of verifying
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that an XML document is an instance of a specified XML <em>schema</em>. An XML schema defines the
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content model (also called a <em>grammar</em> or <em>vocabulary</em>) that its instance documents
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will represent.
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</p>
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<p>
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There are a number of popular technologies available for creating an XML schema. Some of the most
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popular include:
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</p>
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<ul>
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<li><strong>Document Type Definition (DTD)</strong> - XML's built-in schema language.</li>
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<li><strong><a href="http://www.w3.org/XML/Schema">W3C XML Schema (WXS)</a></strong> - an object-oriented XML schema
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language. WXS also provides a type system for constraining the character data of an XML document.
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WXS is maintained by the <a href="http://www.w3.org">World Wide Web Consortium (W3C)</a> and is a W3C
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Recommendation (that is, a ratified W3C standard specification).</li>
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<li><strong><a href="http://www.relaxng.org">RELAX NG (RNG)</a></strong> - a pattern-based,
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user-friendly XML schema language. RNG schemas may also use types to constrain XML character data.
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RNG is maintained by the <a href="http://www.oasis-open.org">Organization for the Advancement of
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Structured Information Standards (OASIS)</a> and is both an OASIS and an
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<a href="http://www.iso.org">ISO (International Organization for Standardization)</a> standard.</li>
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<li><strong><a href="http://www.schematron.com/">Schematron</a></strong> - a rules-based XML schema
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language. Whereas DTD, WXS, and RNG are designed to express the structure of a content model,
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Schematron is designed to enforce individual rules that are difficult or impossible to express
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with other schema languages. Schematron is intended to supplement a schema written in
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structural schema language such as the aforementioned. Schematron is in the process
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of becoming an ISO standard.</li>
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</ul>
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<p>
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Previous versions of JAXP supported validation as a feature of an XML parser, represented by
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either a {@link javax.xml.parsers.SAXParser} or {@link javax.xml.parsers.DocumentBuilder} instance.
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</p>
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<p>
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The JAXP validation API decouples the validation of an instance document from the parsing of an
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XML document. This is advantageous for several reasons, some of which are:
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</p>
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<ul>
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<li><strong>Support for additional schema langauges.</strong> As of JDK 1.5, the two most
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popular JAXP parser implementations, Crimson and Xerces, only support a subset of the available
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XML schema languages. The Validation API provides a standard mechanism through which applications
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may take of advantage of specialization validation libraries which support additional schema
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languages.</li>
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<li><strong>Easy runtime coupling of an XML instance and schema.</strong> Specifying the location
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of a schema to use for validation with JAXP parsers can be confusing. The Validation API makes this
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process simple (see <a href="#example-1">example</a> below).</li>
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</ul>
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<p>
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<a name="example-1"><strong>Usage example</strong>.</a> The following example demonstrates validating
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an XML document with the Validation API (for readability, some exception handling is not shown):
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</p>
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<pre>
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// parse an XML document into a DOM tree
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DocumentBuilder parser = DocumentBuilderFactory.newInstance().newDocumentBuilder();
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Document document = parser.parse(new File("instance.xml"));
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// create a SchemaFactory capable of understanding WXS schemas
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SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
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// load a WXS schema, represented by a Schema instance
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Source schemaFile = new StreamSource(new File("mySchema.xsd"));
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Schema schema = factory.newSchema(schemaFile);
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// create a Validator instance, which can be used to validate an instance document
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Validator validator = schema.newValidator();
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// validate the DOM tree
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try {
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validator.validate(new DOMSource(document));
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} catch (SAXException e) {
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// instance document is invalid!
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}
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</pre>
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<p>
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The JAXP parsing API has been integrated with the Validation API. Applications may create a {@link javax.xml.validation.Schema} with the validation API
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and associate it with a {@link javax.xml.parsers.DocumentBuilderFactory} or a {@link javax.xml.parsers.SAXParserFactory} instance
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by using the {@link javax.xml.parsers.DocumentBuilderFactory#setSchema(Schema)} and {@link javax.xml.parsers.SAXParserFactory#setSchema(Schema)}
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methods. <strong>You should not</strong> both set a schema and call <code>setValidating(true)</code> on a parser factory. The former technique
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will cause parsers to use the new validation API; the latter will cause parsers to use their own internal validation
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facilities. <strong>Turning on both of these options simultaneously will cause either redundant behavior or error conditions.</strong>
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</p>
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</body>
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</html>
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