1 /*
   2  * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /**
  27  * <p>
  28  * Provides an API for validation of XML documents.  <em>Validation</em> is the
  29  * process of verifying that an XML document is an instance of a specified XML
  30  * <em>schema</em>.  An XML schema defines the content model (also called a
  31  * <em>grammar</em> or <em>vocabulary</em>) that its instance documents will
  32  * represent.
  33  * 
  34  * <p>
  35  * There are a number of popular technologies available for creating an XML schema.
  36  * Some of the most popular ones include:
  37  * 
  38  * <ul>
  39  *     <li><strong>Document Type Definition (DTD)</strong>
  40  *         - XML's built-in schema language.
  41  *     </li>
  42  *     <li><strong><a href="http://www.w3.org/XML/Schema">W3C XML Schema (WXS)</a></strong> -
  43  *         an object-oriented XML schema language. WXS also provides a type system
  44  *         for constraining the character data of an XML document. WXS is maintained
  45  *         by the <a href="http://www.w3.org">World Wide Web Consortium (W3C)</a>
  46  *         and is a W3C Recommendation (that is, a ratified W3C standard specification).
  47  *     </li>
  48  *     <li><strong><a href="http://www.relaxng.org">RELAX NG (RNG)</a></strong> -
  49  *         a pattern-based, user-friendly XML schema language. RNG schemas may
  50  *         also use types to constrain XML character data. RNG is maintained by
  51  *         the <a href="http://www.oasis-open.org">Organization for the Advancement
  52  *         of Structured Information Standards (OASIS)</a> and is both an OASIS
  53  *         and an <a href="http://www.iso.org">ISO (International Organization
  54  *         for Standardization)</a> standard.
  55  *     </li>
  56  *     <li><strong><a href="http://www.schematron.com/">Schematron</a></strong> -
  57  *         a rules-based XML schema language. Whereas DTD, WXS, and RNG are designed
  58  *         to express the structure of a content model, Schematron is designed to
  59  *         enforce individual rules that are difficult or impossible to express
  60  *         with other schema languages. Schematron is intended to supplement a
  61  *         schema written in structural schema language such as the aforementioned.
  62  *         Schematron is in the process of becoming an ISO standard.
  63  *     </li>
  64  * </ul>
  65  * <p>
  66  * While JAXP supports validation as a feature of an XML parser, represented by
  67  * either a {@link javax.xml.parsers.SAXParser} or {@link javax.xml.parsers.DocumentBuilder}
  68  * instance, the {@code Validation} API is preferred.
  69  * 
  70  * <p>
  71  * The JAXP validation API decouples the validation of an instance document from
  72  * the parsing of an XML document. This is advantageous for several reasons,
  73  * some of which are:
  74  * 
  75  * <ul>
  76  *     <li><strong>Support for additional schema langauges.</strong>
  77  *         The JAXP parser implementations support only a subset of the available
  78  *         XML schema languages. The Validation API provides a standard mechanism
  79  *         through which applications may take of advantage of specialization
  80  *         validation libraries which support additional schema languages.
  81  *     </li>
  82  *     <li><strong>Easy runtime coupling of an XML instance and schema.</strong>
  83  *         Specifying the location of a schema to use for validation with JAXP
  84  *         parsers can be confusing. The Validation API makes this process simple
  85  *         (see <a href="#example-1">example</a> below).
  86  *     </li>
  87  * </ul>
  88  * <p>
  89  * <a id="example-1"><strong>Usage example</strong>.</a> The following example
  90  * demonstrates validating an XML document with the Validation API
  91  * (for readability, some exception handling is not shown):
  92  * 
  93  * <pre>
  94  *
  95  *     // parse an XML document into a DOM tree
  96  *     DocumentBuilder parser = DocumentBuilderFactory.newInstance().newDocumentBuilder();
  97  *     Document document = parser.parse(new File("instance.xml"));
  98  *
  99  *     // create a SchemaFactory capable of understanding WXS schemas
 100  *     SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
 101  *
 102  *     // load a WXS schema, represented by a Schema instance
 103  *     Source schemaFile = new StreamSource(new File("mySchema.xsd"));
 104  *     Schema schema = factory.newSchema(schemaFile);
 105  *
 106  *     // create a Validator instance, which can be used to validate an instance document
 107  *     Validator validator = schema.newValidator();
 108  *
 109  *     // validate the DOM tree
 110  *     try {
 111  *         validator.validate(new DOMSource(document));
 112  *     } catch (SAXException e) {
 113  *         // instance document is invalid!
 114  *     }
 115  * </pre>
 116  * <p>
 117  * The JAXP parsing API has been integrated with the Validation API. Applications
 118  * may create a {@link javax.xml.validation.Schema} with the validation API
 119  * and associate it with a {@link javax.xml.parsers.DocumentBuilderFactory} or
 120  * a {@link javax.xml.parsers.SAXParserFactory} instance by using the
 121  * {@link javax.xml.parsers.DocumentBuilderFactory#setSchema(Schema)} and
 122  * {@link javax.xml.parsers.SAXParserFactory#setSchema(Schema)} methods.
 123  * <strong>You should not</strong> both set a schema and call <code>setValidating(true)</code>
 124  * on a parser factory. The former technique will cause parsers to use the new
 125  * validation API; the latter will cause parsers to use their own internal validation
 126  * facilities. <strong>Turning on both of these options simultaneously will cause
 127  * either redundant behavior or error conditions.</strong>
 128  * 
 129  *
 130  * @since 1.5
 131  */
 132 
 133 package javax.xml.validation;