DefaultHandler2

AI-generated Key Takeaways

• DefaultHandler2 is a convenience class extending SAX2's DefaultHandler to support Lexical, Decl, and EntityResolver2 functionalities for comprehensive XML parsing.

• It provides default, often empty, implementations for new handler methods, allowing developers to override only the necessary ones for custom event handling.

• LexicalHandler interface focuses on reporting lexical events like comments, CDATA sections, and DTD declarations, providing fine-grained control over XML parsing.

• Both DefaultHandler2 and LexicalHandler are part of the SAX API, enabling applications to handle specific XML elements for low-level document processing and manipulation.

• LexicalHandler methods throw SAXException for processing errors and might throw IOException for input/output issues, notably during entity resolution.

public class DefaultHandler2 extends DefaultHandler
implements LexicalHandler DeclHandler EntityResolver2

This class extends the SAX2 base handler class to support the SAX2 LexicalHandler, DeclHandler, and EntityResolver2 extensions. Except for overriding the original SAX1 resolveEntity() method the added handler methods just return. Subclassers may override everything on a method-by-method basis.

This module, both source code and documentation, is in the Public Domain, and comes with NO WARRANTY.

Note: this class might yet learn that the ContentHandler.setDocumentLocator() call might be passed a Locator2 object, and that the ContentHandler.startElement() call might be passed a Attributes2 object.

Public Constructor Summary

DefaultHandler2() Constructs a handler which ignores all parsing events.

Public Method Summary

void	attributeDecl(String eName, String aName, String type, String mode, String value) Report an attribute type declaration.
void	comment(char[] ch, int start, int length) Report an XML comment anywhere in the document.
void	elementDecl(String name, String model) Report an element type declaration.
void	endCDATA() Report the end of a CDATA section.
void	endDTD() Report the end of DTD declarations.
void	endEntity(String name) Report the end of an entity.
void	externalEntityDecl(String name, String publicId, String systemId) Report a parsed external entity declaration.
InputSource	getExternalSubset(String name, String baseURI) Tells the parser that if no external subset has been declared in the document text, none should be used.
void	internalEntityDecl(String name, String value) Report an internal entity declaration.
InputSource	resolveEntity(String publicId, String systemId) Invokes EntityResolver2.resolveEntity() with null entity name and base URI.
InputSource	resolveEntity(String name, String publicId, String baseURI, String systemId) Tells the parser to resolve the systemId against the baseURI and read the entity text from that resulting absolute URI.
void	startCDATA() Report the start of a CDATA section.
void	startDTD(String name, String publicId, String systemId) Report the start of DTD declarations, if any.
void	startEntity(String name) Report the beginning of some internal and external XML entities.

Inherited Method Summary

From class org.xml.sax.helpers.DefaultHandler

void	characters(char[] ch, int start, int length) Receive notification of character data inside an element.
void	endDocument() Receive notification of the end of the document.
void	endElement(String uri, String localName, String qName) Receive notification of the end of an element.
void	endPrefixMapping(String prefix) Receive notification of the end of a Namespace mapping.
void	error(SAXParseException e) Receive notification of a recoverable parser error.
void	fatalError(SAXParseException e) Report a fatal XML parsing error.
void	ignorableWhitespace(char[] ch, int start, int length) Receive notification of ignorable whitespace in element content.
void	notationDecl(String name, String publicId, String systemId) Receive notification of a notation declaration.
void	processingInstruction(String target, String data) Receive notification of a processing instruction.
InputSource	resolveEntity(String publicId, String systemId) Resolve an external entity.
void	setDocumentLocator(Locator locator) Receive a Locator object for document events.
void	skippedEntity(String name) Receive notification of a skipped entity.
void	startDocument() Receive notification of the beginning of the document.
void	startElement(String uri, String localName, String qName, Attributes attributes) Receive notification of the start of an element.
void	startPrefixMapping(String prefix, String uri) Receive notification of the start of a Namespace mapping.
void	unparsedEntityDecl(String name, String publicId, String systemId, String notationName) Receive notification of an unparsed entity declaration.
void	warning(SAXParseException e) Receive notification of a parser warning.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface org.xml.sax.EntityResolver

abstract InputSource

resolveEntity(String publicId, String systemId) Allow the application to resolve external entities.

From interface org.xml.sax.DTDHandler

abstract void	notationDecl(String name, String publicId, String systemId) Receive notification of a notation declaration event.
abstract void	unparsedEntityDecl(String name, String publicId, String systemId, String notationName) Receive notification of an unparsed entity declaration event.

From interface org.xml.sax.ContentHandler

abstract void	characters(char[] ch, int start, int length) Receive notification of character data.
abstract void	endDocument() Receive notification of the end of a document.
abstract void	endElement(String uri, String localName, String qName) Receive notification of the end of an element.
abstract void	endPrefixMapping(String prefix) End the scope of a prefix-URI mapping.
abstract void	ignorableWhitespace(char[] ch, int start, int length) Receive notification of ignorable whitespace in element content.
abstract void	processingInstruction(String target, String data) Receive notification of a processing instruction.
abstract void	setDocumentLocator(Locator locator) Receive an object for locating the origin of SAX document events.
abstract void	skippedEntity(String name) Receive notification of a skipped entity.
abstract void	startDocument() Receive notification of the beginning of a document.
abstract void	startElement(String uri, String localName, String qName, Attributes atts) Receive notification of the beginning of an element.
abstract void	startPrefixMapping(String prefix, String uri) Begin the scope of a prefix-URI Namespace mapping.

From interface org.xml.sax.ErrorHandler

abstract void	error(SAXParseException exception) Receive notification of a recoverable error.
abstract void	fatalError(SAXParseException exception) Receive notification of a non-recoverable error.
abstract void	warning(SAXParseException exception) Receive notification of a warning.

From interface org.xml.sax.ext.LexicalHandler

abstract void	comment(char[] ch, int start, int length) Report an XML comment anywhere in the document.
abstract void	endCDATA() Report the end of a CDATA section.
abstract void	endDTD() Report the end of DTD declarations.
abstract void	endEntity(String name) Report the end of an entity.
abstract void	startCDATA() Report the start of a CDATA section.
abstract void	startDTD(String name, String publicId, String systemId) Report the start of DTD declarations, if any.
abstract void	startEntity(String name) Report the beginning of some internal and external XML entities.

From interface org.xml.sax.ext.DeclHandler

abstract void	attributeDecl(String eName, String aName, String type, String mode, String value) Report an attribute type declaration.
abstract void	elementDecl(String name, String model) Report an element type declaration.
abstract void	externalEntityDecl(String name, String publicId, String systemId) Report a parsed external entity declaration.
abstract void	internalEntityDecl(String name, String value) Report an internal entity declaration.

From interface org.xml.sax.ext.EntityResolver2

abstract InputSource	getExternalSubset(String name, String baseURI) Allows applications to provide an external subset for documents that don't explicitly define one.
abstract InputSource	resolveEntity(String name, String publicId, String baseURI, String systemId) Allows applications to map references to external entities into input sources, or tell the parser it should use conventional URI resolution.

Public Constructors

public DefaultHandler2 ()

Constructs a handler which ignores all parsing events.

Public Methods

public void attributeDecl (String eName, String aName, String type, String mode, String value)

Report an attribute type declaration.

Only the effective (first) declaration for an attribute will be reported. The type will be one of the strings "CDATA", "ID", "IDREF", "IDREFS", "NMTOKEN", "NMTOKENS", "ENTITY", "ENTITIES", a parenthesized token group with the separator "|" and all whitespace removed, or the word "NOTATION" followed by a space followed by a parenthesized token group with all whitespace removed.

The value will be the value as reported to applications, appropriately normalized and with entity and character references expanded.

Parameters

eName	The name of the associated element.
aName	The name of the attribute.
type	A string representing the attribute type.
mode	A string representing the attribute defaulting mode ("#IMPLIED", "#REQUIRED", or "#FIXED") or null if none of these applies.
value	A string representing the attribute's default value, or null if there is none.

Throws

SAXException

public void comment (char[] ch, int start, int length)

Report an XML comment anywhere in the document.

This callback will be used for comments inside or outside the document element, including comments in the external DTD subset (if read). Comments in the DTD must be properly nested inside start/endDTD and start/endEntity events (if used).

Parameters

ch	An array holding the characters in the comment.
start	The starting position in the array.
length	The number of characters to use from the array.

Throws

SAXException

public void elementDecl (String name, String model)

Report an element type declaration.

The content model will consist of the string "EMPTY", the string "ANY", or a parenthesised group, optionally followed by an occurrence indicator. The model will be normalized so that all parameter entities are fully resolved and all whitespace is removed,and will include the enclosing parentheses. Other normalization (such as removing redundant parentheses or simplifying occurrence indicators) is at the discretion of the parser.

Parameters

name	The element type name.
model	The content model as a normalized string.

Throws

SAXException

public void endCDATA ()

Report the end of a CDATA section.

Throws

SAXException

public void endDTD ()

Report the end of DTD declarations.

This method is intended to report the end of the DOCTYPE declaration; if the document has no DOCTYPE declaration, this method will not be invoked.

Throws

SAXException

public void endEntity (String name)

Report the end of an entity.

Parameters

name	The name of the entity that is ending.

Throws

SAXException

public void externalEntityDecl (String name, String publicId, String systemId)

Report a parsed external entity declaration.

Only the effective (first) declaration for each entity will be reported.

If the system identifier is a URL, the parser must resolve it fully before passing it to the application.

Parameters

name	The name of the entity. If it is a parameter entity, the name will begin with '%'.
publicId	The entity's public identifier, or null if none was given.
systemId	The entity's system identifier.

Throws

SAXException

public InputSource getExternalSubset (String name, String baseURI)

Tells the parser that if no external subset has been declared in the document text, none should be used.

Parameters

name	Identifies the document root element. This name comes from a DOCTYPE declaration (where available) or from the actual root element. The parameter is ignored.
baseURI	The document's base URI, serving as an additional hint for selecting the external subset. This is always an absolute URI, unless it is null because the XMLReader was given an InputSource without one. The parameter is ignored.

Returns

• null (always).

Throws

SAXException	Any SAX exception, possibly wrapping another exception.
IOException	Probably indicating a failure to create a new InputStream or Reader, or an illegal URL.

public void internalEntityDecl (String name, String value)

Report an internal entity declaration.

Only the effective (first) declaration for each entity will be reported. All parameter entities in the value will be expanded, but general entities will not.

Parameters

name	The name of the entity. If it is a parameter entity, the name will begin with '%'.
value	The replacement text of the entity.

Throws

SAXException

public InputSource resolveEntity (String publicId, String systemId)

Invokes EntityResolver2.resolveEntity() with null entity name and base URI. You only need to override that method to use this class.

Parameters

publicId	The public identifier of the external entity being referenced (normalized as required by the XML specification), or null if none was supplied.
systemId	The system identifier of the external entity being referenced; either a relative or absolute URI. This is never null when invoked by a SAX2 parser; only declared entities, and any external subset, are resolved by such parsers.

Returns

• An InputSource object describing the new input source.

Throws

SAXException	Any SAX exception, possibly wrapping another exception.
IOException	Probably indicating a failure to create a new InputStream or Reader, or an illegal URL.

public InputSource resolveEntity (String name, String publicId, String baseURI, String systemId)

Tells the parser to resolve the systemId against the baseURI and read the entity text from that resulting absolute URI. Note that because the older DefaultHandler.resolveEntity(), method is overridden to call this one, this method may sometimes be invoked with null name and baseURI, and with the systemId already absolutized.

Parameters

name	Identifies the external entity being resolved. Either "[dtd]" for the external subset, or a name starting with "%" to indicate a parameter entity, or else the name of a general entity. This is never null when invoked by a SAX2 parser.
publicId	The public identifier of the external entity being referenced (normalized as required by the XML specification), or null if none was supplied.
baseURI	The URI with respect to which relative systemIDs are interpreted. This is always an absolute URI, unless it is null (likely because the XMLReader was given an InputSource without one). This URI is defined by the XML specification to be the one associated with the "<" starting the relevant declaration.
systemId	The system identifier of the external entity being referenced; either a relative or absolute URI. This is never null when invoked by a SAX2 parser; only declared entities, and any external subset, are resolved by such parsers.

Returns

• An InputSource object describing the new input source.

Throws

SAXException	Any SAX exception, possibly wrapping another exception.
IOException	Probably indicating a failure to create a new InputStream or Reader, or an illegal URL.

public void startCDATA ()

Report the start of a CDATA section.

The contents of the CDATA section will be reported through the regular characters event; this event is intended only to report the boundary.

Throws

SAXException

public void startDTD (String name, String publicId, String systemId)

Report the start of DTD declarations, if any.

This method is intended to report the beginning of the DOCTYPE declaration; if the document has no DOCTYPE declaration, this method will not be invoked.

All declarations reported through DTDHandler or DeclHandler events must appear between the startDTD and endDTD events. Declarations are assumed to belong to the internal DTD subset unless they appear between startEntity and endEntity events. Comments and processing instructions from the DTD should also be reported between the startDTD and endDTD events, in their original order of (logical) occurrence; they are not required to appear in their correct locations relative to DTDHandler or DeclHandler events, however.

Note that the start/endDTD events will appear within the start/endDocument events from ContentHandler and before the first startElement event.

Parameters

name	The document type name.
publicId	The declared public identifier for the external DTD subset, or null if none was declared.
systemId	The declared system identifier for the external DTD subset, or null if none was declared. (Note that this is not resolved against the document base URI.)

Throws

SAXException

public void startEntity (String name)

Report the beginning of some internal and external XML entities.

The reporting of parameter entities (including the external DTD subset) is optional, and SAX2 drivers that report LexicalHandler events may not implement it; you can use the http://xml.org/sax/features/lexical-handler/parameter-entities feature to query or control the reporting of parameter entities.

General entities are reported with their regular names, parameter entities have '%' prepended to their names, and the external DTD subset has the pseudo-entity name "[dtd]".

When a SAX2 driver is providing these events, all other events must be properly nested within start/end entity events. There is no additional requirement that events from DeclHandler or DTDHandler be properly ordered.

Note that skipped entities will be reported through the skippedEntity event, which is part of the ContentHandler interface.

Because of the streaming event model that SAX uses, some entity boundaries cannot be reported under any circumstances:

• general entities within attribute values
• parameter entities within declarations

These will be silently expanded, with no indication of where the original entity boundaries were.

Note also that the boundaries of character references (which are not really entities anyway) are not reported.

All start/endEntity events must be properly nested.

Parameters

name	The name of the entity. If it is a parameter entity, the name will begin with '%', and if it is the external DTD subset, it will be "[dtd]".

Throws

SAXException