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 * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package javax.xml;


Utility class to contain basic XML values as constants.

Author:Jeff Suttor
See Also:
Since:1.5
/**
 * <p>Utility class to contain basic XML values as constants.
 *
 * @author Jeff Suttor
 * @see <a href="http://www.w3.org/TR/xml11/">Extensible Markup Language (XML) 1.1</a>
 * @see <a href="http://www.w3.org/TR/REC-xml">Extensible Markup Language (XML) 1.0 (Second Edition)</a>
 * @see <a href="http://www.w3.org/XML/xml-V10-2e-errata">XML 1.0 Second Edition Specification Errata</a>
 * @see <a href="http://www.w3.org/TR/xml-names11/">Namespaces in XML 1.1</a>
 * @see <a href="http://www.w3.org/TR/REC-xml-names">Namespaces in XML</a>
 * @see <a href="http://www.w3.org/TR/xmlschema-1/">XML Schema Part 1: Structures</a>
 * @since 1.5
 **/

public final class XMLConstants {

    
Private constructor to prevent instantiation.

/**
     * Private constructor to prevent instantiation.
     */
    private XMLConstants() {
    }

    
Namespace URI to use to represent that there is no Namespace.

Defined by the Namespace specification to be "".

See Also:
/**
     * Namespace URI to use to represent that there is no Namespace.
     *
     * <p>Defined by the Namespace specification to be "".
     *
     * @see <a href="http://www.w3.org/TR/REC-xml-names/#defaulting">
     * Namespaces in XML, 5.2 Namespace Defaulting</a>
     */
    public static final String NULL_NS_URI = "";

    
Prefix to use to represent the default XML Namespace.

Defined by the XML specification to be "".

See Also:
/**
     * Prefix to use to represent the default XML Namespace.
     *
     * <p>Defined by the XML specification to be "".
     *
     * @see <a
     * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">
     * Namespaces in XML, 3. Qualified Names</a>
     */
    public static final String DEFAULT_NS_PREFIX = "";

    
The official XML Namespace name URI.

Defined by the XML specification to be "http://www.w3.org/XML/1998/namespace". 
See Also:
/**
     * The official XML Namespace name URI.
     *
     * <p>Defined by the XML specification to be
     * "{@code http://www.w3.org/XML/1998/namespace}".
     *
     * @see <a
     * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">
     * Namespaces in XML, 3. Qualified Names</a>
     */
    public static final String XML_NS_URI =
        "http://www.w3.org/XML/1998/namespace";

    
The official XML Namespace prefix.

Defined by the XML specification to be "xml". 
See Also:
/**
     * The official XML Namespace prefix.
     *
     * <p>Defined by the XML specification to be "{@code xml}".
     *
     * @see <a
     * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">
     * Namespaces in XML, 3. Qualified Names</a>
     */
    public static final String XML_NS_PREFIX = "xml";

    
The official XML attribute used for specifying XML Namespace declarations, 
XMLConstants.XMLNS_ATTRIBUTE, Namespace name URI. 
Defined by the XML specification to be "http://www.w3.org/2000/xmlns/". 
See Also:
/**
     * The official XML attribute used for specifying XML Namespace
     * declarations, {@link #XMLNS_ATTRIBUTE
     * XMLConstants.XMLNS_ATTRIBUTE}, Namespace name URI.
     *
     * <p>Defined by the XML specification to be
     * "{@code http://www.w3.org/2000/xmlns/}".
     *
     * @see <a
     * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">
     * Namespaces in XML, 3. Qualified Names</a>
     */
    public static final String XMLNS_ATTRIBUTE_NS_URI =
        "http://www.w3.org/2000/xmlns/";

    
The official XML attribute used for specifying XML Namespace
declarations.

It is NOT valid to use as a prefix. Defined by the XML specification to be "xmlns". 
See Also:
/**
     * The official XML attribute used for specifying XML Namespace
     * declarations.
     *
     * <p>It is <strong><em>NOT</em></strong> valid to use as a
     * prefix.  Defined by the XML specification to be
     * "{@code xmlns}".
     *
     * @see <a
     * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">
     * Namespaces in XML, 3. Qualified Names</a>
     */
    public static final String XMLNS_ATTRIBUTE = "xmlns";

    
W3C XML Schema Namespace URI.

Defined to be "http://www.w3.org/2001/XMLSchema". 
See Also:
/**
     * W3C XML Schema Namespace URI.
     *
     * <p>Defined to be "{@code http://www.w3.org/2001/XMLSchema}".
     *
     * @see <a href=
     *  "http://www.w3.org/TR/xmlschema-1/#Instance_Document_Constructions">
     *  XML Schema Part 1:
     *  Structures, 2.6 Schema-Related Markup in Documents Being Validated</a>
     */
    public static final String W3C_XML_SCHEMA_NS_URI =
        "http://www.w3.org/2001/XMLSchema";

    
W3C XML Schema Instance Namespace URI.

Defined to be "http://www.w3.org/2001/XMLSchema-instance". 
See Also:
/**
     * W3C XML Schema Instance Namespace URI.
     *
     * <p>Defined to be "{@code http://www.w3.org/2001/XMLSchema-instance}".
     *
     * @see <a href=
     *  "http://www.w3.org/TR/xmlschema-1/#Instance_Document_Constructions">
     *  XML Schema Part 1:
     *  Structures, 2.6 Schema-Related Markup in Documents Being Validated</a>
     */
    public static final String W3C_XML_SCHEMA_INSTANCE_NS_URI =
        "http://www.w3.org/2001/XMLSchema-instance";

    
W3C XPath Datatype Namespace URI.

Defined to be "http://www.w3.org/2003/11/xpath-datatypes". 
See Also:
/**
     * W3C XPath Datatype Namespace URI.
     *
     * <p>Defined to be "{@code http://www.w3.org/2003/11/xpath-datatypes}".
     *
     * @see <a href="http://www.w3.org/TR/xpath-datamodel">XQuery 1.0 and XPath 2.0 Data Model</a>
     */
    public static final String W3C_XPATH_DATATYPE_NS_URI = "http://www.w3.org/2003/11/xpath-datatypes";

    
XML Document Type Declaration Namespace URI as an arbitrary value.

Since not formally defined by any existing standard, arbitrarily define to be "http://www.w3.org/TR/REC-xml". 
/**
     * XML Document Type Declaration Namespace URI as an arbitrary value.
     *
     * <p>Since not formally defined by any existing standard, arbitrarily define to be "{@code http://www.w3.org/TR/REC-xml}".
     */
    public static final String XML_DTD_NS_URI = "http://www.w3.org/TR/REC-xml";

        
RELAX NG Namespace URI.

Defined to be "http://relaxng.org/ns/structure/1.0". 
See Also:
/**
         * RELAX NG Namespace URI.
         *
         * <p>Defined to be "{@code http://relaxng.org/ns/structure/1.0}".
         *
         * @see <a href="http://relaxng.org/spec-20011203.html">RELAX NG Specification</a>
         */
        public static final String RELAXNG_NS_URI = "http://relaxng.org/ns/structure/1.0";

        
Feature for secure processing.

    
  
  •  true instructs the implementation to process XML securely. This may set limits on XML constructs to avoid conditions such as denial of service attacks. 
    • 
  
  •  false instructs the implementation to process XML in accordance with the XML specifications ignoring security issues such as limits on XML constructs to avoid conditions such as denial of service attacks. 
    • 



/**
         * Feature for secure processing.
         *
         * <ul>
         *   <li>
         *     {@code true} instructs the implementation to process XML securely.
         *     This may set limits on XML constructs to avoid conditions such as denial of service attacks.
         *   </li>
         *   <li>
         *     {@code false} instructs the implementation to process XML in accordance with the XML specifications
         *     ignoring security issues such as limits on XML constructs to avoid conditions such as denial of service attacks.
         *   </li>
         * </ul>
         */
        public static final String FEATURE_SECURE_PROCESSING = "http://javax.xml.XMLConstants/feature/secure-processing";


        
Property: accessExternalDTD

 Restrict access to external DTDs and external Entity References to the protocols specified. If access is denied due to the restriction of this property, a runtime exception that is specific to the context is thrown. In the case of SAXParser for example, SAXException is thrown. 

Value:  a list of protocols separated by comma. A protocol is the scheme portion of a URI, or in the case of the JAR protocol, "jar" plus the scheme portion separated by colon. A scheme is defined as: 

scheme = alpha *( alpha | digit | "+" | "-" | "." )

where alpha = a-z and A-Z.


And the JAR protocol:

jar[:scheme]

 Protocols including the keyword "jar" are case-insensitive. Any whitespaces as defined by Character.isSpaceChar in the value will be ignored. Examples of protocols are file, http, jar:file. 



Default value: The default value is implementation specific and therefore not specified.
The following options are provided for consideration:



    
    
  • an empty string to deny all access to external references;
    • 
    
  • a specific protocol, such as file, to give permission to only the protocol;
    • 
    
  • the keyword "all" to grant  permission to all protocols.
    • 



     When FEATURE_SECURE_PROCESSING is enabled,  it is recommended that implementations
     restrict external connections by default, though this may cause problems for applications
     that process XML/XSD/XSL with external references.




Granting all access:  the keyword "all" grants permission to all protocols.


System Property: The value of this property can be set or overridden by system property javax.xml.accessExternalDTD. 

jaxp.properties: This configuration file is in standard Properties format and typically located in the conf directory of the Java installation. If the file exists and the system property is specified, its value will be used to override the default of the property. 
Since:1.7
/**
         * Property: accessExternalDTD
         *
         * <p>
         * Restrict access to external DTDs and external Entity References to the protocols specified.
         * If access is denied due to the restriction of this property, a runtime exception that
         * is specific to the context is thrown. In the case of {@link javax.xml.parsers.SAXParser}
         * for example, {@link org.xml.sax.SAXException} is thrown.
         *
         * <p>
         * <b>Value: </b> a list of protocols separated by comma. A protocol is the scheme portion of a
         * {@link java.net.URI}, or in the case of the JAR protocol, "jar" plus the scheme portion
         * separated by colon.
         * A scheme is defined as:
         *
         * <blockquote>
         * scheme = alpha *( alpha | digit | "+" | "-" | "." )<br>
         * where alpha = a-z and A-Z.<br><br>
         *
         * And the JAR protocol:<br>
         *
         * jar[:scheme]<br><br>
         *
         * Protocols including the keyword "jar" are case-insensitive. Any whitespaces as defined by
         * {@link java.lang.Character#isSpaceChar } in the value will be ignored.
         * Examples of protocols are file, http, jar:file.
         *
         * </blockquote>
         *
         *<p>
         * <b>Default value:</b> The default value is implementation specific and therefore not specified.
         * The following options are provided for consideration:
         * <blockquote>
         * <UL>
         *     <LI>an empty string to deny all access to external references;</LI>
         *     <LI>a specific protocol, such as file, to give permission to only the protocol;</LI>
         *     <LI>the keyword "all" to grant  permission to all protocols.</LI>
         * </UL><br>
         *      When FEATURE_SECURE_PROCESSING is enabled,  it is recommended that implementations
         *      restrict external connections by default, though this may cause problems for applications
         *      that process XML/XSD/XSL with external references.
         * </blockquote>
         *
         * <p>
         * <b>Granting all access:</b>  the keyword "all" grants permission to all protocols.
         *
         * <p>
         * <b>System Property:</b> The value of this property can be set or overridden by
         * system property {@code javax.xml.accessExternalDTD}.
         *
         *
         * <p>
         * <b>jaxp.properties:</b> This configuration file is in standard
         * {@link java.util.Properties} format and typically located in the {@code conf}
         * directory of the Java installation. If the file exists and the system
         * property is specified, its value will be used to override the default
         * of the property.
         *
         *
         * @since 1.7
         */
        public static final String ACCESS_EXTERNAL_DTD = "http://javax.xml.XMLConstants/property/accessExternalDTD";

        
Property: accessExternalSchema


 Restrict access to the protocols specified for external reference set by the schemaLocation attribute, Import and Include element. If access is denied due to the restriction of this property, a runtime exception that is specific to the context is thrown. In the case of SchemaFactory for example, org.xml.sax.SAXException is thrown. 

Value: a list of protocols separated by comma. A protocol is the scheme portion of a URI, or in the case of the JAR protocol, "jar" plus the scheme portion separated by colon. A scheme is defined as: 

scheme = alpha *( alpha | digit | "+" | "-" | "." )

where alpha = a-z and A-Z.


And the JAR protocol:

jar[:scheme]

 Protocols including the keyword "jar" are case-insensitive. Any whitespaces as defined by Character.isSpaceChar in the value will be ignored. Examples of protocols are file, http, jar:file. 



Default value: The default value is implementation specific and therefore not specified.
The following options are provided for consideration:



    
    
  • an empty string to deny all access to external references;
    • 
    
  • a specific protocol, such as file, to give permission to only the protocol;
    • 
    
  • the keyword "all" to grant  permission to all protocols.
    • 



     When FEATURE_SECURE_PROCESSING is enabled,  it is recommended that implementations
     restrict external connections by default, though this may cause problems for applications
     that process XML/XSD/XSL with external references.




Granting all access:  the keyword "all" grants permission to all protocols.


System Property: The value of this property can be set or overridden by system property javax.xml.accessExternalSchema 

jaxp.properties: This configuration file is in standard Properties format and typically located in the conf directory of the Java installation. If the file exists and the system property is specified, its value will be used to override the default of the property. 
Since:1.7
/**
         * <p>Property: accessExternalSchema</p>
         *
         * <p>
         * Restrict access to the protocols specified for external reference set by the
         * schemaLocation attribute, Import and Include element. If access is denied
         * due to the restriction of this property, a runtime exception that is specific
         * to the context is thrown. In the case of {@link javax.xml.validation.SchemaFactory}
         * for example, org.xml.sax.SAXException is thrown.
         *
         * <p>
         * <b>Value:</b> a list of protocols separated by comma. A protocol is the scheme portion of a
         * {@link java.net.URI}, or in the case of the JAR protocol, "jar" plus the scheme portion
         * separated by colon.
         * A scheme is defined as:
         *
         * <blockquote>
         * scheme = alpha *( alpha | digit | "+" | "-" | "." )<br>
         * where alpha = a-z and A-Z.<br><br>
         *
         * And the JAR protocol:<br>
         *
         * jar[:scheme]<br><br>
         *
         * Protocols including the keyword "jar" are case-insensitive. Any whitespaces as defined by
         * {@link java.lang.Character#isSpaceChar } in the value will be ignored.
         * Examples of protocols are file, http, jar:file.
         *
         * </blockquote>
         *
         * <p>
         * <b>Default value:</b> The default value is implementation specific and therefore not specified.
         * The following options are provided for consideration:
         * <blockquote>
         * <UL>
         *     <LI>an empty string to deny all access to external references;</LI>
         *     <LI>a specific protocol, such as file, to give permission to only the protocol;</LI>
         *     <LI>the keyword "all" to grant  permission to all protocols.</LI>
         * </UL><br>
         *      When FEATURE_SECURE_PROCESSING is enabled,  it is recommended that implementations
         *      restrict external connections by default, though this may cause problems for applications
         *      that process XML/XSD/XSL with external references.
         * </blockquote>
         *
         * <p>
         * <b>Granting all access:</b>  the keyword "all" grants permission to all protocols.
         *
         * <p>
         * <b>System Property:</b> The value of this property can be set or overridden by
         * system property {@code javax.xml.accessExternalSchema}
         *
         * <p>
         * <b>jaxp.properties:</b> This configuration file is in standard
         * {@link java.util.Properties} format and typically located in the {@code conf}
         * directory of the Java installation. If the file exists and the system
         * property is specified, its value will be used to override the default
         * of the property.
         *
         * @since 1.7
         */
        public static final String ACCESS_EXTERNAL_SCHEMA = "http://javax.xml.XMLConstants/property/accessExternalSchema";

        
Property: accessExternalStylesheet

 Restrict access to the protocols specified for external references set by the stylesheet processing instruction, Import and Include element, and document function. If access is denied due to the restriction of this property, a runtime exception that is specific to the context is thrown. In the case of constructing new Transformer for example, TransformerConfigurationException will be thrown by the TransformerFactory. 

Value: a list of protocols separated by comma. A protocol is the scheme portion of a URI, or in the case of the JAR protocol, "jar" plus the scheme portion separated by colon. A scheme is defined as: 

scheme = alpha *( alpha | digit | "+" | "-" | "." )

where alpha = a-z and A-Z.


And the JAR protocol:

jar[:scheme]

 Protocols including the keyword "jar" are case-insensitive. Any whitespaces as defined by Character.isSpaceChar in the value will be ignored. Examples of protocols are file, http, jar:file. 



Default value: The default value is implementation specific and therefore not specified.
The following options are provided for consideration:



    
    
  • an empty string to deny all access to external references;
    • 
    
  • a specific protocol, such as file, to give permission to only the protocol;
    • 
    
  • the keyword "all" to grant  permission to all protocols.
    • 



     When FEATURE_SECURE_PROCESSING is enabled,  it is recommended that implementations
     restrict external connections by default, though this may cause problems for applications
     that process XML/XSD/XSL with external references.




Granting all access:  the keyword "all" grants permission to all protocols.


System Property: The value of this property can be set or overridden by system property javax.xml.accessExternalStylesheet 

jaxp.properties: This configuration file is in standard Properties format and typically located in the conf directory of the Java installation. If the file exists and the system property is specified, its value will be used to override the default of the property. 
Since:1.7
/**
         * Property: accessExternalStylesheet
         *
         * <p>
         * Restrict access to the protocols specified for external references set by the
         * stylesheet processing instruction, Import and Include element, and document function.
         * If access is denied due to the restriction of this property, a runtime exception
         * that is specific to the context is thrown. In the case of constructing new
         * {@link javax.xml.transform.Transformer} for example,
         * {@link javax.xml.transform.TransformerConfigurationException}
         * will be thrown by the {@link javax.xml.transform.TransformerFactory}.
         *
         * <p>
         * <b>Value:</b> a list of protocols separated by comma. A protocol is the scheme portion of a
         * {@link java.net.URI}, or in the case of the JAR protocol, "jar" plus the scheme portion
         * separated by colon.
         * A scheme is defined as:
         *
         * <blockquote>
         * scheme = alpha *( alpha | digit | "+" | "-" | "." )<br>
         * where alpha = a-z and A-Z.<br><br>
         *
         * And the JAR protocol:<br>
         *
         * jar[:scheme]<br><br>
         *
         * Protocols including the keyword "jar" are case-insensitive. Any whitespaces as defined by
         * {@link java.lang.Character#isSpaceChar } in the value will be ignored.
         * Examples of protocols are file, http, jar:file.
         *
         * </blockquote>
         *
         * <p>
         * <b>Default value:</b> The default value is implementation specific and therefore not specified.
         * The following options are provided for consideration:
         * <blockquote>
         * <UL>
         *     <LI>an empty string to deny all access to external references;</LI>
         *     <LI>a specific protocol, such as file, to give permission to only the protocol;</LI>
         *     <LI>the keyword "all" to grant  permission to all protocols.</LI>
         * </UL><br>
         *      When FEATURE_SECURE_PROCESSING is enabled,  it is recommended that implementations
         *      restrict external connections by default, though this may cause problems for applications
         *      that process XML/XSD/XSL with external references.
         * </blockquote>
         *
         * <p>
         * <b>Granting all access:</b>  the keyword "all" grants permission to all protocols.
         *
         * <p>
         * <b>System Property:</b> The value of this property can be set or overridden by
         * system property {@code javax.xml.accessExternalStylesheet}
         *
         * <p>
         * <b>jaxp.properties:</b> This configuration file is in standard
         * {@link java.util.Properties} format and typically located in the {@code conf}
         * directory of the Java installation. If the file exists and the system
         * property is specified, its value will be used to override the default
         * of the property.
         *
         * @since 1.7
         */
        public static final String ACCESS_EXTERNAL_STYLESHEET = "http://javax.xml.XMLConstants/property/accessExternalStylesheet";


        
Feature: useCatalog

 Instructs XML processors to use XML Catalogs to resolve entity references. Catalogs may be set through JAXP factories, system properties, or jaxp.properties by using the javax.xml.catalog.files property defined in CatalogFeatures. The following code enables Catalog on SAX parser: 

     SAXParserFactory spf = SAXParserFactory.newInstance();
     spf.setFeature(XMLConstants.USE_CATALOG, true);
     SAXParser parser = spf.newSAXParser();
     parser.setProperty(CatalogFeatures.Feature.FILES.getPropertyName(), "catalog.xml");




Value: a boolean. If the value is true, and a catalog is set, the XML parser will resolve external references using CatalogResolver. If the value is false, XML Catalog is ignored even if one is set. The default value is true. 

System Property: The value of this property can be set or overridden by system property javax.xml.useCatalog 

jaxp.properties: This configuration file is in standard Properties format and typically located in the conf directory of the Java installation. If the file exists and the system property is specified, its value will be used to override the default value of the property. 
Since:9
/**
         * Feature: useCatalog
         *
         * <p>
         * Instructs XML processors to use XML Catalogs to resolve entity references.
         * Catalogs may be set through JAXP factories, system properties, or
         * jaxp.properties by using the {@code javax.xml.catalog.files} property
         * defined in {@link javax.xml.catalog.CatalogFeatures}.
         * The following code enables Catalog on SAX parser:
         * <pre>{@code
         *      SAXParserFactory spf = SAXParserFactory.newInstance();
         *      spf.setFeature(XMLConstants.USE_CATALOG, true);
         *      SAXParser parser = spf.newSAXParser();
         *      parser.setProperty(CatalogFeatures.Feature.FILES.getPropertyName(), "catalog.xml");
         * }</pre>
         *
         * <p>
         * <b>Value:</b> a boolean. If the value is true, and a catalog is set,
         * the XML parser will resolve external references using
         * {@link javax.xml.catalog.CatalogResolver}. If the value is false,
         * XML Catalog is ignored even if one is set. The default value is true.
         *
         * <p>
         * <b>System Property:</b> The value of this property can be set or overridden by
         * system property {@code javax.xml.useCatalog}
         *
         * <p>
         * <b>jaxp.properties:</b> This configuration file is in standard
         * {@link java.util.Properties} format and typically located in the {@code conf}
         * directory of the Java installation. If the file exists and the system
         * property is specified, its value will be used to override the default
         * value of the property.
         *
         * @since 9
         */
        public static final String USE_CATALOG = "http://javax.xml.XMLConstants/feature/useCatalog";

}