xml/validation/package.html

325N/A<?xml version="1.0" encoding="UTF-8"?>
325N/A<!--
325N/ACopyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
325N/ADO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
325N/A
325N/AThis code is free software; you can redistribute it and/or modify it
325N/Aunder the terms of the GNU General Public License version 2 only, as
325N/Apublished by the Free Software Foundation.  Oracle designates this
325N/Aparticular file as subject to the "Classpath" exception as provided
325N/Aby Oracle in the LICENSE file that accompanied this code.
325N/A
325N/AThis code is distributed in the hope that it will be useful, but WITHOUT
325N/AANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
325N/AFITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
325N/Aversion 2 for more details (a copy is included in the LICENSE file that
325N/Aaccompanied this code).
325N/A
325N/AYou should have received a copy of the GNU General Public License version
325N/A2 along with this work; if not, write to the Free Software Foundation,
325N/AInc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
325N/A
325N/APlease contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
325N/Aor visit www.oracle.com if you need additional information or have any
325N/Aquestions.
325N/A-->
325N/A
325N/A<!DOCTYPE html
325N/A     PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
325N/A     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
325N/A
<html xmlns="http://www.w3.org/1999/xhtml">

<head>
  <title>javax.xml.validation</title>

  <meta name="CVS"
        content="$Id: package.html,v 1.2 2005/06/10 03:50:43 jeffsuttor Exp $" />
  <meta name="AUTHOR"
        content="Jeff.Suttor@Sun.com" />
</head>
    <body>
        <p>
            This package provides an API for validation of XML documents.  <em>Validation</em> is the process of verifying
            that an XML document is an instance of a specified XML <em>schema</em>.  An XML schema defines the
            content model (also called a <em>grammar</em> or <em>vocabulary</em>) that its instance documents
            will represent.
        </p>
        <p>
            There are a number of popular technologies available for creating an XML schema. Some of the most
            popular include:
        </p>
            <ul>
                <li><strong>Document Type Definition (DTD)</strong> - XML's built-in schema language.</li>
                <li><strong><a href="http://www.w3.org/XML/Schema">W3C XML Schema (WXS)</a></strong> - an object-oriented XML schema
                    language. WXS also provides a type system for constraining the character data of an XML document.
                    WXS is maintained by the <a href="http://www.w3.org">World Wide Web Consortium (W3C)</a> and is a W3C
                    Recommendation (that is, a ratified W3C standard specification).</li>
                <li><strong><a href="http://www.relaxng.org">RELAX NG (RNG)</a></strong> - a pattern-based,
                    user-friendly XML schema language. RNG schemas may also use types to constrain XML character data.
                    RNG is maintained by the <a href="http://www.oasis-open.org">Organization for the Advancement of
                    Structured Information Standards (OASIS)</a> and is both an OASIS and an
                    <a href="http://www.iso.org">ISO (International Organization for Standardization)</a> standard.</li>
                <li><strong><a href="http://www.schematron.com/">Schematron</a></strong> - a rules-based XML schema
                language. Whereas DTD, WXS, and RNG are designed to express the structure of a content model,
                Schematron is designed to enforce individual rules that are difficult or impossible to express
                with other schema languages. Schematron is intended to supplement a schema written in
                structural schema language such as the aforementioned. Schematron is in the process
                of becoming an ISO standard.</li>
            </ul>
        <p>
            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.
        </p>
        <p>
            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:
        </p>
            <ul>
                <li><strong>Support for additional schema langauges.</strong> As of JDK 1.5, the two most
                popular JAXP parser implementations, Crimson and Xerces, only support 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.</li>
                <li><strong>Easy runtime coupling of an XML instance and schema.</strong> Specifying the location
                of a schema to use for validation with JAXP parsers can be confusing. The Validation API makes this
                process simple (see <a href="#example-1">example</a> below).</li>
          </ul>
        <p>
            <a name="example-1"><strong>Usage example</strong>.</a> The following example demonstrates validating
            an XML document with the Validation API (for readability, some exception handling is not shown):
        </p>
            <pre>

    // 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!
    }
</pre>
        <p>
            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. <strong>You should not</strong> both set a schema and call <code>setValidating(true)</code> 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. <strong>Turning on both of these options simultaneously will cause either redundant behavior or error conditions.</strong>
        </p>
    </body>
</html>