Module java.xml

module java.xml
Defines the Java APIs for XML Processing (JAXP).

The JAXP APIs

JAXP comprises a set of APIs built upon a number of XML technologies and standards that are essential for XML processing. These include APIs for:

Factories and Processors

Factories are the entry points of each API, providing methods to allow applications to set JAXP Properties programmatically, before creating processors. The Configuration section provides more details on this. Factories also support the JAXP Lookup Mechanism, in which applications can be deployed with third party implementations to use instead of JDK implementations

Processors are aggregates of parsers (or readers), serializers (or writers), validators, and transformers that control and perform the processing in their respective areas. They are defined in their relevant packages. In the parsers package for example, are the DocumentBuilder and SAXParser, that represent the DOM and SAX processors.

The processors are configured and instantiated with their corresponding factories. The DocumentBuilder and SAXParser for example are constructed with the DocumentBuilderFactory and SAXParserFactory respectively.

Configuration

When a JAXP factory is invoked for the first time, it performs a configuration process to determine the implementation to be used and its subsequent behaviors. During configuration, the factory examines configuration sources such as the JAXP Properties, System Properties, and the JAXP Configuration File, and sets the values following the Property Precedence. The terminologies and process are defined below.

JAXP Properties

JAXP properties are configuration settings that are applied to XML processors. They can be used to control and customize the behavior of a processor. Depending on the JAXP API that is being used, JAXP properties may be referred to as Attributes, Properties, or Features.

System Properties

Select JAXP properties have corresponding System Properties allowing the properties to be set at runtime, on the command line, or within the JAXP Configuration File. For example, the System Property javax.xml.catalog.resolve may be used to set the CatalogFeatures' RESOLVE property.

The exact time at which system properties are read is unspecified. In order to ensure that the desired values are properly applied, applications should ensure that system properties are set appropriately prior to the creation of the first JAXP factory and are not modified thereafter.

Configuration File

JAXP supports the use of configuration files for specifying the implementation class to load for the JAXP factories as well as for setting JAXP properties.

Configuration files are Java Properties files that consist of mappings between system properties and their values defined by various APIs or processes. The following configuration file entries demonstrate setting the javax.xml.parsers.DocumentBuilderFactory and CatalogFeatures.RESOLVE properties: 

   javax.xml.parsers.DocumentBuilderFactory=packagename.DocumentBuilderFactoryImpl
   javax.xml.catalog.resolve=strict

jaxp.properties File

By default, JAXP looks for the configuration file jaxp.properties, located in the ${java.home}/conf directory; and if the file exists, loads the specified properties to customize the behavior of the XML factories and processors.

The jaxp.properties file will be read only once during the initialization of the JAXP implementation and cached in memory. If there is an error accessing or reading the file, the configuration process proceeds as if the file does not exist.

User-defined Configuration File

In addition to the jaxp.properties file, the system property java.xml.config.file can be set to specify the location of a configuration file. If the java.xml.config.file property is included within a configuration file, it will be ignored.

When the java.xml.config.file is specified, the configuration file will be read and the included properties will override the same properties that were defined in the jaxp.properties file. If the java.xml.config.file has not been set when the JAXP implementation is initialized, no further attempt will be made to check for its existence.

The java.xml.config.file value must contain a valid pathname to a configuration file. If the pathname is not absolute, it will be considered relative to the working directory of the JVM. If there is an error reading the configuration file, the configuration process proceeds as if the java.xml.config.file property was not set. Implementations may optionally issue a warning message.

Property Precedence

JAXP properties can be set in multiple ways, including by API methods, system properties, and the JAXP Configuration File. When not explicitly set, they will be initialized with default values or more restrictive values when FEATURE_SECURE_PROCESSING (FSP) is enabled. The configuration order of precedence for properties is as follows, from highest to lowest:

  • The APIs for factories or processors

  • System Property

  • User-defined Configuration File

  • The default JAXP Configuration File jaxp.properties

  • The default values for JAXP Properties. If the FSP is true, the default values will be set to process XML securely.

Using the CatalogFeatures' RESOLVE property as an example, the following illustrates how these rules are applied:

  • Properties specified with factory or processor APIs have the highest precedence. The following code effectively sets the RESOLVE property to strict, regardless of settings in any other configuration sources. 

       DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
   dbf.setAttribute(CatalogFeatures.Feature.RESOLVE.getPropertyName(), "strict");

  • If the property is not set on the factory as in the above code, a system property setting will be in effect. 

        // in the following example, the RESOLVE property is set to 'continue'
    // for the entire application
    java -Djavax.xml.catalog.resolve=continue myApp

  • If the property is not set on the factory, or using a system property, the setting in a configuration file will take effect. The following entry sets the property to 'continue'. 

        javax.xml.catalog.resolve=continue

  • If the property is not set anywhere, it will be resolved to its default value that is 'strict'.

JAXP Lookup Mechanism

JAXP defines an ordered lookup procedure to determine the implementation class to load for the JAXP factories. Factories that support the mechanism are listed in the table below along with the method, System Property, and System Default method to be used in the procedure.
JAXP Factories
Factory Method System Property System Default
DatatypeFactory newInstance() javax.xml.datatype.DatatypeFactory newDefaultInstance()
DocumentBuilderFactory newInstance() javax.xml.parsers.DocumentBuilderFactory newDefaultInstance()
SAXParserFactory newInstance() javax.xml.parsers.SAXParserFactory newDefaultInstance()
XMLEventFactory newFactory() javax.xml.stream.XMLEventFactory newDefaultFactory()
XMLInputFactory newFactory() javax.xml.stream.XMLInputFactory newDefaultFactory()
XMLOutputFactory newFactory() javax.xml.stream.XMLOutputFactory newDefaultFactory()
TransformerFactory newInstance() javax.xml.transform.TransformerFactory newDefaultInstance()
SchemaFactory newInstance(schemaLanguage) javax.xml.validation.SchemaFactory:schemaLanguage[1] newDefaultInstance()
XPathFactory newInstance(uri) DEFAULT_PROPERTY_NAME + ":uri"[2] newDefaultInstance()
[1] where schemaLanguage is the parameter to the newInstance(schemaLanguage) method.

[2] where uri is the parameter to the newInstance(uri) method.

Lookup Procedure

The order of precedence for locating the implementation class of a JAXP Factory is as follows, from highest to lowest:
Implementation Note:

JDK built-in Catalog

The JDK has a built-in catalog that hosts the following DTDs defined by the Java Platform:

The catalog is loaded once when the first JAXP processor factory is created.

External Resource Resolution Process with the built-in Catalog

The JDK creates a CatalogResolver with the built-in catalog when needed. This CatalogResolver is used as the default external resource resolver.

XML processors may use resolvers (such as EntityResolver, XMLResolver, and CatalogResolver) to handle external references. In the absence of the user-defined resolvers, the JDK XML processors fall back to the default CatalogResolver to attempt to find a resolution before making a connection to fetch the resources. The fall-back also takes place if a user-defined resolver exists but allows the process to continue when unable to resolve the resource.

If the default CatalogResolver is unable to locate a resource, it may signal the XML processors to continue processing, or skip the resource, or throw a CatalogException. The behavior is configured with the jdk.xml.jdkcatalog.resolve property.

Implementation Specific Properties

In addition to the standard JAXP Properties, the JDK implementation supports a number of implementation specific properties whose name is prefixed by "jdk.xml.". These properties also follow the configuration process as defined in the Configuration section.

Refer to the Implementation Specific Properties table for the list of properties supported by the JDK implementation.

Processor Support

The properties may be supported by one or more processors as listed in the table below. Depending on the type of the property, they may be set via Method 1: setAttribute/Parameter/Property or 2: setFeature as illustrated in the relevant columns.
Processors
ID Name Method 1: setAttribute/Parameter/Property Method 2: setFeature
DOM DOM Parser DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setAttribute(name, value); 		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setFeature(name, value);
SAX SAX Parser SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser parser = spf.newSAXParser();
parser.setProperty(name, value); 		SAXParserFactory spf = SAXParserFactory.newInstance();
spf.setFeature(name, value);
StAX StAX Parser XMLInputFactory xif = XMLInputFactory.newInstance();
xif.setProperty(name, value); 		XMLInputFactory xif = XMLInputFactory.newInstance();
xif.setProperty(name, value);
Validation XML Validation API SchemaFactory schemaFactory = SchemaFactory.newInstance(schemaLanguage);
schemaFactory.setProperty(name, value); 		SchemaFactory schemaFactory = SchemaFactory.newInstance(schemaLanguage);
schemaFactory.setFeature(name, value);
Transform XML Transform API TransformerFactory factory = TransformerFactory.newInstance();
factory.setAttribute(name, value); 		TransformerFactory factory = TransformerFactory.newInstance();
factory.setFeature(name, value);
XSLTC Serializer XSLTC Serializer Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(name, value);
DOMLS DOM Load and Save LSSerializer serializer = domImplementation.createLSSerializer();
serializer.getDomConfig().setParameter(name, value);
XPath XPath XPathFactory factory = XPathFactory.newInstance();
factory.setProperty(name, value); 		XPathFactory factory = XPathFactory.newInstance();
factory.setFeature(name, value);
Implementation Specific Properties
Full Name (prefix jdk.xml.) [1] Description System Property [2] Value [3] Security [4] Supported Processor [5] Since [6]
Type Value Default Enforced ID Set Method
jdk.xml.entityExpansionLimit Limits the number of entity expansions. yes Integer A positive integer. A value less than or equal to 0 indicates no limit. If the value is not an integer, a NumberFormatException is thrown. 64000 64000 Yes DOM
SAX
StAX
Validation
Transform 		Method 1 8
jdk.xml.elementAttributeLimit Limits the number of attributes an element can have. 10000 10000
jdk.xml.maxOccurLimit Limits the number of content model nodes that may be created when building a grammar for a W3C XML Schema that contains maxOccurs attributes with values other than "unbounded". 5000 5000
jdk.xml.totalEntitySizeLimit Limits the total size of all entities that include general and parameter entities. The size is calculated as an aggregation of all entities. 5x10^7 5x10^7
jdk.xml.maxGeneralEntitySizeLimit Limits the maximum size of any general entities. 0 0
jdk.xml.maxParameterEntitySizeLimit Limits the maximum size of any parameter entities, including the result of nesting multiple parameter entities. 10^6 10^6
jdk.xml.entityReplacementLimit Limits the total number of nodes in all entity references. 3x10^6 3x10^6
jdk.xml.maxElementDepth Limits the maximum element depth. 0 0
jdk.xml.maxXMLNameLimit Limits the maximum size of XML names, including element name, attribute name and namespace prefix and URI. 1000 1000
jdk.xml.isStandalone Indicates that the serializer should treat the output as a standalone document. The property can be used to ensure a newline is written after the XML declaration. Unlike the property xml-declaration, this property does not have an effect on whether an XML declaration should be written out. boolean true/false false N/A No DOMLS 17
jdk.xml.xsltcIsStandalone Indicates that the XSLTC serializer should treat the output as a standalone document. The property can be used to ensure a newline is written after the XML declaration. Unlike the property OMIT_XML_DECLARATION, this property does not have an effect on whether an XML declaration should be written out.

This property behaves similar to that for DOMLS above, except that it is for the XSLTC Serializer and its value is a String.

String yes/no no N/A No XSLTC Serializer 17
jdk.xml.cdataChunkSize Instructs the parser to return the data in a CData section in a single chunk when the property is zero or unspecified, or in multiple chunks when it is greater than zero. The parser shall split the data by linebreaks, and any chunks that are larger than the specified size to ones that are equal to or smaller than the size. yes Integer A positive integer. A value less than or equal to 0 indicates that the property is not specified. If the value is not an integer, a NumberFormatException is thrown. 0 N/A No SAX
StAX		 9
jdk.xml.extensionClassLoader Sets a non-null ClassLoader instance to be used for loading XSLTC java extension functions. no Object A reference to a ClassLoader object. Null if the value is not specified. null N/A No Transform 9
jdk.xml.xpathExprGrpLimit Limits the number of groups an XPath expression can contain. yes Integer A positive integer. A value less than or equal to 0 indicates no limit. If the value is not an integer, a NumberFormatException is thrown. 10 10 Yes Transform
XPath 		19
jdk.xml.xpathExprOpLimit Limits the number of operators an XPath expression can contain. 100 100
jdk.xml.xpathTotalOpLimit Limits the total number of XPath operators in an XSL Stylesheet. 10000 10000 Transform
jdk.xml.enableExtensionFunctions Determines if XSLT and XPath extension functions are to be allowed. yes Boolean true or false. True indicates that extension functions are allowed; False otherwise. true false Yes Transform
XPath 		Method 2 8
jdk.xml.overrideDefaultParser Enables the use of a 3rd party's parser implementation to override the system-default parser for the JDK's Transform, Validation and XPath implementations. true or false. True enables the use of 3rd party's parser implementations to override the system-default implementation during XML Transform, Validation or XPath operation. False disables the use of 3rd party's parser implementations. false false Yes Transform
Validation
XPath 		Method 2 9
jdk.xml.resetSymbolTable Instructs the parser to reset its internal symbol table during each parse operation. true or false. True indicates that the SymbolTable associated with a parser needs to be reallocated during each parse operation.
False indicates that the parser's SymbolTable instance shall be reused during subsequent parse operations. 		false N/A No SAX Method 2 9
jdk.xml.dtd.support[7] Instructs the parser to handle DTDs in accordance with the setting of this property. The options are:

  • allow -- indicates that the parser shall continue processing DTDs;

  • ignore -- indicates that the parser shall skip DTDs;

  • deny -- indicates that the parser shall reject DTDs as an error. The parser shall report the error in accordance with its relevant specification.

String allow, ignore, and deny. Values are case-insensitive. allow No Yes DOM
SAX
StAX
Validation
Transform 		Method 1 22
jdk.xml.jdkcatalog.resolve Instructs the JDK default CatalogResolver to act in accordance with the setting of this property when unable to resolve an external reference with the built-in Catalog. The options are:

  • continue -- Indicates that the processing should continue

  • ignore -- Indicates that the reference is skipped

  • strict -- Indicates that the resolver should throw a CatalogException

String continue, ignore, and strict. Values are case-insensitive. continue No Yes DOM
SAX
StAX
Validation
Transform 		Method 1 22

[1] The full name of a property should be used to set the property.

[2] A value "yes" indicates there is a corresponding System Property for the property, "no" otherwise. The name of the System Property is the same as that of the property.

[3] The value must be exactly as listed in this table, case-sensitive. The value of the corresponding System Property is the String representation of the property value. If the type is boolean, the system property is true only if it is "true"; If the type is String, the system property is true only if it is exactly the same string representing the positive value (e.g. "yes" for xsltcIsStandalone); The system property is false otherwise. If the type is Integer, the value of the System Property is the String representation of the value (e.g. "64000" for entityExpansionLimit).

[4] A value "yes" indicates the property is a Security Property. As indicated in the Property Precedence, the values listed in the column enforced will be used to initialize these properties when FSP is true.

[5] One or more processors that support the property. The IDs and Set Method are as shown in the table Processors.

[6] Indicates the initial release the property is introduced.

[7] The jdk.xml.dtd.support property complements the two existing DTD-related properties, disallow-doctype-decl(fully qualified name: http://apache.org/xml/features/disallow-doctype-decl) and supportDTD (javax.xml.stream.supportDTD), by providing a uniformed support for the processors listed and a system property that can be used in the JAXP Configuration File. When disallow-doctype-decl is set on the DOM or SAX factory, or supportDTD on StAX factory, the jdk.xml.dtd.support property will have no effect.

These three properties control whether DTDs as a whole shall be processed. When they are set to deny or ignore, other properties that regulate a part or an aspect of DTD shall have no effect.

Legacy Property Names (deprecated)

JDK releases prior to JDK 17 support the use of URI style prefix for properties. These legacy property names are deprecated as of JDK 17 and may be removed in future releases. If both new and legacy properties are set, the new property names take precedence regardless of how and where they are set. The overriding order as defined in Property Precedence thus becomes:
  • Value set on factories or processors using new property names.
  • Value set on factories or processors using legacy property names;
  • Value set as System Property;
  • Value set in the configuration file;
  • Value set by FEATURE_SECURE_PROCESSING;
  • The default value;

The following table lists the properties and their corresponding legacy names.

Legacy Property Names (deprecated since 17)
Property Legacy Property Name(s)
jdk.xml.entityExpansionLimit http://www.oracle.com/xml/jaxp/properties/entityExpansionLimit
jdk.xml.elementAttributeLimit http://www.oracle.com/xml/jaxp/properties/elementAttributeLimit
jdk.xml.maxOccurLimit http://www.oracle.com/xml/jaxp/properties/maxOccurLimit
jdk.xml.totalEntitySizeLimit http://www.oracle.com/xml/jaxp/properties/totalEntitySizeLimit
jdk.xml.maxGeneralEntitySizeLimit http://www.oracle.com/xml/jaxp/properties/maxGeneralEntitySizeLimit
jdk.xml.maxParameterEntitySizeLimit http://www.oracle.com/xml/jaxp/properties/maxParameterEntitySizeLimit
jdk.xml.entityReplacementLimit http://www.oracle.com/xml/jaxp/properties/entityReplacementLimit
jdk.xml.maxElementDepth http://www.oracle.com/xml/jaxp/properties/maxElementDepth
jdk.xml.maxXMLNameLimit http://www.oracle.com/xml/jaxp/properties/maxXMLNameLimit
jdk.xml.isStandalone http://www.oracle.com/xml/jaxp/properties/isStandalone
jdk.xml.xsltcIsStandalone http://www.oracle.com/xml/is-standalone
http://www.oracle.com/xml/jaxp/properties/xsltcIsStandalone
jdk.xml.extensionClassLoader jdk.xml.transform.extensionClassLoader
jdk.xml.enableExtensionFunctions http://www.oracle.com/xml/jaxp/properties/enableExtensionFunctions

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