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Java Source Code / Java Documentation » Development » Javolution » org.xml.sax 
Source Cross Reference  Class Diagram Java Document (Java Doc) 


org.xml.sax.ContentHandler

ContentHandler
public interface ContentHandler (Code)
Receive notification of the logical content of a document.
This module, both source code and documentation, is in the Public Domain, and comes with NO WARRANTY. See http://www.saxproject.org for further information.

This is the main interface that most SAX applications implement: if the application needs to be informed of basic parsing events, it implements this interface and registers an instance with the SAX parser using the org.xml.sax.XMLReader.setContentHandler setContentHandler method. The parser uses the instance to report basic document-related events like the start and end of elements and character data.

The order of events in this interface is very important, and mirrors the order of information in the document itself. For example, all of an element's content (character data, processing instructions, and/or subelements) will appear, in order, between the startElement event and the corresponding endElement event.

This interface is similar to the now-deprecated SAX 1.0 DocumentHandler interface, but it adds support for Namespaces and for reporting skipped entities (in non-validating XML processors).

Implementors should note that there is also a ContentHandler class in the java.net package; that means that it's probably a bad idea to do

import java.net.*;
 import org.xml.sax.*;
 

In fact, "import ...*" is usually a sign of sloppy programming anyway, so the user should consider this a feature rather than a bug.


since:
   SAX 2.0
author:
   David Megginson
version:
   2.0.1+ (sax2r3pre1)
See Also:   org.xml.sax.XMLReader
See Also:   org.xml.sax.DTDHandler
See Also:   org.xml.sax.ErrorHandler




Method Summary
public  voidcharacters(char ch, int start, int length)
     Receive notification of character data.

The Parser will call this method to report each chunk of character data.

public  voidendDocument()
     Receive notification of the end of a document.

There is an apparent contradiction between the documentation for this method and the documentation for org.xml.sax.ErrorHandler.fatalError .

public  voidendElement(String uri, String localName, String qName)
     Receive notification of the end of an element.
public  voidendPrefixMapping(String prefix)
     End the scope of a prefix-URI mapping.

See ContentHandler.startPrefixMapping startPrefixMapping for details.

public  voidignorableWhitespace(char ch, int start, int length)
     Receive notification of ignorable whitespace in element content.
public  voidprocessingInstruction(String target, String data)
     Receive notification of a processing instruction.

The Parser will invoke this method once for each processing instruction found: note that processing instructions may occur before or after the main document element.

A SAX parser must never report an XML declaration (XML 1.0, section 2.8) or a text declaration (XML 1.0, section 4.3.1) using this method.

Like ContentHandler.characters characters() , processing instruction data may have characters that need more than one char value.

public  voidsetDocumentLocator(Locator locator)
     Receive an object for locating the origin of SAX document events.

SAX parsers are strongly encouraged (though not absolutely required) to supply a locator: if it does so, it must supply the locator to the application by invoking this method before invoking any of the other methods in the ContentHandler interface.

The locator allows the application to determine the end position of any document-related event, even if the parser is not reporting an error.

public  voidskippedEntity(String name)
     Receive notification of a skipped entity. This is not called for entity references within markup constructs such as element start tags or markup declarations.
public  voidstartDocument()
     Receive notification of the beginning of a document.
public  voidstartElement(String uri, String localName, String qName, Attributes atts)
     Receive notification of the beginning of an element.

The Parser will invoke this method at the beginning of every element in the XML document; there will be a corresponding ContentHandler.endElement endElement event for every startElement event (even when the element is empty).

public  voidstartPrefixMapping(String prefix, String uri)
     Begin the scope of a prefix-URI Namespace mapping.



Method Detail
characters
public void characters(char ch, int start, int length) throws SAXException(Code)
Receive notification of character data.

The Parser will call this method to report each chunk of character data. SAX parsers may return all contiguous character data in a single chunk, or they may split it into several chunks; however, all of the characters in any single event must come from the same external entity so that the Locator provides useful information.

The application must not attempt to read from the array outside of the specified range.

Individual characters may consist of more than one Java char value. There are two important cases where this happens, because characters can't be represented in just sixteen bits. In one case, characters are represented in a Surrogate Pair, using two special Unicode values. Such characters are in the so-called "Astral Planes", with a code point above U+FFFF. A second case involves composite characters, such as a base character combining with one or more accent characters.

Your code should not assume that algorithms using char-at-a-time idioms will be working in character units; in some cases they will split characters. This is relevant wherever XML permits arbitrary characters, such as attribute values, processing instruction data, and comments as well as in data reported from this method. It's also generally relevant whenever Java code manipulates internationalized text; the issue isn't unique to XML.

Note that some parsers will report whitespace in element content using the ContentHandler.ignorableWhitespace ignorableWhitespace method rather than this one (validating parsers must do so).


Parameters:
  ch - the characters from the XML document
Parameters:
  start - the start position in the array
Parameters:
  length - the number of characters to read from the array
throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception
See Also:   ContentHandler.ignorableWhitespace
See Also:   
See Also:   org.xml.sax.Locator



endDocument
public void endDocument() throws SAXException(Code)
Receive notification of the end of a document.

There is an apparent contradiction between the documentation for this method and the documentation for org.xml.sax.ErrorHandler.fatalError . Until this ambiguity is resolved in a future major release, clients should make no assumptions about whether endDocument() will or will not be invoked when the parser has reported a fatalError() or thrown an exception.

The SAX parser will invoke this method only once, and it will be the last method invoked during the parse. The parser shall not invoke this method until it has either abandoned parsing (because of an unrecoverable error) or reached the end of input.


throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception
See Also:   ContentHandler.startDocument



endElement
public void endElement(String uri, String localName, String qName) throws SAXException(Code)
Receive notification of the end of an element.

The SAX parser will invoke this method at the end of every element in the XML document; there will be a corresponding ContentHandler.startElement startElement event for every endElement event (even when the element is empty).

For information on the names, see startElement.


Parameters:
  uri - the Namespace URI, or the empty string if theelement has no Namespace URI or if Namespaceprocessing is not being performed
Parameters:
  localName - the local name (without prefix), or theempty string if Namespace processing is not beingperformed
Parameters:
  qName - the qualified XML name (with prefix), or theempty string if qualified names are not available
throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception



endPrefixMapping
public void endPrefixMapping(String prefix) throws SAXException(Code)
End the scope of a prefix-URI mapping.

See ContentHandler.startPrefixMapping startPrefixMapping for details. These events will always occur immediately after the corresponding ContentHandler.endElement endElement event, but the order of ContentHandler.endPrefixMapping endPrefixMapping events is not otherwise guaranteed.


Parameters:
  prefix - the prefix that was being mapped.This is the empty string when a default mapping scope ends.
throws:
  org.xml.sax.SAXException - the client may throwan exception during processing
See Also:   ContentHandler.startPrefixMapping
See Also:   ContentHandler.endElement



ignorableWhitespace
public void ignorableWhitespace(char ch, int start, int length) throws SAXException(Code)
Receive notification of ignorable whitespace in element content.

Validating Parsers must use this method to report each chunk of whitespace in element content (see the W3C XML 1.0 recommendation, section 2.10): non-validating parsers may also use this method if they are capable of parsing and using content models.

SAX parsers may return all contiguous whitespace in a single chunk, or they may split it into several chunks; however, all of the characters in any single event must come from the same external entity, so that the Locator provides useful information.

The application must not attempt to read from the array outside of the specified range.


Parameters:
  ch - the characters from the XML document
Parameters:
  start - the start position in the array
Parameters:
  length - the number of characters to read from the array
throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception
See Also:   ContentHandler.characters



processingInstruction
public void processingInstruction(String target, String data) throws SAXException(Code)
Receive notification of a processing instruction.

The Parser will invoke this method once for each processing instruction found: note that processing instructions may occur before or after the main document element.

A SAX parser must never report an XML declaration (XML 1.0, section 2.8) or a text declaration (XML 1.0, section 4.3.1) using this method.

Like ContentHandler.characters characters() , processing instruction data may have characters that need more than one char value.


Parameters:
  target - the processing instruction target
Parameters:
  data - the processing instruction data, or null ifnone was supplied. The data does not include anywhitespace separating it from the target
throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception



setDocumentLocator
public void setDocumentLocator(Locator locator)(Code)
Receive an object for locating the origin of SAX document events.

SAX parsers are strongly encouraged (though not absolutely required) to supply a locator: if it does so, it must supply the locator to the application by invoking this method before invoking any of the other methods in the ContentHandler interface.

The locator allows the application to determine the end position of any document-related event, even if the parser is not reporting an error. Typically, the application will use this information for reporting its own errors (such as character content that does not match an application's business rules). The information returned by the locator is probably not sufficient for use with a search engine.

Note that the locator will return correct information only during the invocation SAX event callbacks after ContentHandler.startDocument startDocument returns and before ContentHandler.endDocument endDocument is called. The application should not attempt to use it at any other time.


Parameters:
  locator - an object that can return the location ofany SAX document event
See Also:   org.xml.sax.Locator



skippedEntity
public void skippedEntity(String name) throws SAXException(Code)
Receive notification of a skipped entity. This is not called for entity references within markup constructs such as element start tags or markup declarations. (The XML recommendation requires reporting skipped external entities. SAX also reports internal entity expansion/non-expansion, except within markup constructs.)

The Parser will invoke this method each time the entity is skipped. Non-validating processors may skip entities if they have not seen the declarations (because, for example, the entity was declared in an external DTD subset). All processors may skip external entities, depending on the values of the http://xml.org/sax/features/external-general-entities and the http://xml.org/sax/features/external-parameter-entities properties.


Parameters:
  name - the name of the skipped entity. If it is a parameter entity, the name will begin with '%', and ifit is the external DTD subset, it will be the string"[dtd]"
throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception



startDocument
public void startDocument() throws SAXException(Code)
Receive notification of the beginning of a document.

The SAX parser will invoke this method only once, before any other event callbacks (except for ContentHandler.setDocumentLocator setDocumentLocator ).


throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception
See Also:   ContentHandler.endDocument



startElement
public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException(Code)
Receive notification of the beginning of an element.

The Parser will invoke this method at the beginning of every element in the XML document; there will be a corresponding ContentHandler.endElement endElement event for every startElement event (even when the element is empty). All of the element's content will be reported, in order, before the corresponding endElement event.

This event allows up to three name components for each element:

  1. the Namespace URI;
  2. the local name; and
  3. the qualified (prefixed) name.

Any or all of these may be provided, depending on the values of the http://xml.org/sax/features/namespaces and the http://xml.org/sax/features/namespace-prefixes properties:

  • the Namespace URI and local name are required when the namespaces property is true (the default), and are optional when the namespaces property is false (if one is specified, both must be);
  • the qualified name is required when the namespace-prefixes property is true, and is optional when the namespace-prefixes property is false (the default).

Note that the attribute list provided will contain only attributes with explicit values (specified or defaulted): #IMPLIED attributes will be omitted. The attribute list will contain attributes used for Namespace declarations (xmlns* attributes) only if the http://xml.org/sax/features/namespace-prefixes property is true (it is false by default, and support for a true value is optional).

Like ContentHandler.characters characters() , attribute values may have characters that need more than one char value.


Parameters:
  uri - the Namespace URI, or the empty string if theelement has no Namespace URI or if Namespaceprocessing is not being performed
Parameters:
  localName - the local name (without prefix), or theempty string if Namespace processing is not beingperformed
Parameters:
  qName - the qualified name (with prefix), or theempty string if qualified names are not available
Parameters:
  atts - the attributes attached to the element. Ifthere are no attributes, it shall be an emptyAttributes object. The value of this object afterstartElement returns is undefined
throws:
  org.xml.sax.SAXException - any SAX exception, possiblywrapping another exception
See Also:   ContentHandler.endElement
See Also:   org.xml.sax.Attributes
See Also:   org.xml.sax.helpers.SaxAttributes



startPrefixMapping
public void startPrefixMapping(String prefix, String uri) throws SAXException(Code)
Begin the scope of a prefix-URI Namespace mapping.

The information from this event is not necessary for normal Namespace processing: the SAX XML reader will automatically replace prefixes for element and attribute names when the http://xml.org/sax/features/namespaces feature is true (the default).

There are cases, however, when applications need to use prefixes in character data or in attribute values, where they cannot safely be expanded automatically; the start/endPrefixMapping event supplies the information to the application to expand prefixes in those contexts itself, if necessary.

Note that start/endPrefixMapping events are not guaranteed to be properly nested relative to each other: all startPrefixMapping events will occur immediately before the corresponding ContentHandler.startElement startElement event, and all ContentHandler.endPrefixMapping endPrefixMapping events will occur immediately after the corresponding ContentHandler.endElement endElement event, but their order is not otherwise guaranteed.

There should never be start/endPrefixMapping events for the "xml" prefix, since it is predeclared and immutable.


Parameters:
  prefix - the Namespace prefix being declared.An empty string is used for the default element namespace,which has no prefix.
Parameters:
  uri - the Namespace URI the prefix is mapped to
throws:
  org.xml.sax.SAXException - the client may throwan exception during processing
See Also:   ContentHandler.endPrefixMapping
See Also:   ContentHandler.startElement



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