Module java.xml

Package javax.xml.stream

Interface XMLStreamReader

All Superinterfaces:

XMLStreamConstants

All Known Implementing Classes:

StreamReaderDelegate

public interface XMLStreamReader
extends XMLStreamConstants

The XMLStreamReader interface allows forward, read-only access to XML. It is designed to be the lowest level and most efficient way to read XML data.

The XMLStreamReader is designed to iterate over XML using next() and hasNext(). The data can be accessed using methods such as getEventType(), getNamespaceURI(), getLocalName() and getText();

An XMLStreamReader instance is created with an initial event type START_DOCUMENT. At any moment in time, it has a current event that the methods of the interface access and may load the next event through the next() method. The current event type can be determined by getEventType(), and the next returned by the next() method.

Parsing events are defined as the XML Declaration, a DTD, start tag, character data, white space, end tag, comment, or processing instruction. An attribute or namespace event may be encountered at the root level of a document as the result of a query operation.

For XML 1.0 compliance an XML processor must pass the identifiers of declared unparsed entities, notation declarations and their associated identifiers to the application. This information is provided through the property API on this interface. The following two properties allow access to this information: javax.xml.stream.notations and javax.xml.stream.entities. When the current event is a DTD the following call will return a list of Notations List l = (List) getProperty("javax.xml.stream.notations"); The following call will return a list of entity declarations: List l = (List) getProperty("javax.xml.stream.entities"); These properties can only be accessed during a DTD event and are defined to return null if the information is not available.

The following table describes which methods are valid in what state. If a method is called in an invalid state the method will throw a java.lang.IllegalStateException.

Valid methods for each state

Event Type	Valid Methods
All States	getProperty(), hasNext(), require(), close(), getNamespaceURI(), isStartElement(), isEndElement(), isCharacters(), isWhiteSpace(), getNamespaceContext(), getEventType(),getLocation(), hasText(), hasName()
START_ELEMENT	next(), getName(), getLocalName(), hasName(), getPrefix(), getAttributeXXX(), isAttributeSpecified(), getNamespaceXXX(), getElementText(), nextTag()
ATTRIBUTE	next(), nextTag() getAttributeXXX(), isAttributeSpecified(),
NAMESPACE	next(), nextTag() getNamespaceXXX()
END_ELEMENT	next(), getName(), getLocalName(), hasName(), getPrefix(), getNamespaceXXX(), nextTag()
CHARACTERS	next(), getTextXXX(), nextTag()
CDATA	next(), getTextXXX(), nextTag()
COMMENT	next(), getTextXXX(), nextTag()
SPACE	next(), getTextXXX(), nextTag()
START_DOCUMENT	next(), getEncoding(), getVersion(), isStandalone(), standaloneSet(), getCharacterEncodingScheme(), nextTag()
END_DOCUMENT	close()
PROCESSING_INSTRUCTION	next(), getPITarget(), getPIData(), nextTag()
ENTITY_REFERENCE	next(), getLocalName(), getText(), nextTag()
DTD	next(), getText(), nextTag()

Since:

1.6

See Also:

XMLEvent, XMLInputFactory, XMLStreamWriter

Field Summary

Fields declared in interface javax.xml.stream.XMLStreamConstants

ATTRIBUTE, CDATA, CHARACTERS, COMMENT, DTD, END_DOCUMENT, END_ELEMENT, ENTITY_DECLARATION, ENTITY_REFERENCE, NAMESPACE, NOTATION_DECLARATION, PROCESSING_INSTRUCTION, SPACE, START_DOCUMENT, START_ELEMENT

Method Summary

Modifier and Type	Method	Description
void	close()	Frees any resources associated with this Reader.
int	getAttributeCount()	Returns the count of attributes on this START_ELEMENT, this method is only valid on a START_ELEMENT or ATTRIBUTE.
String	getAttributeLocalName(int index)	Returns the localName of the attribute at the provided index
QName	getAttributeName(int index)	Returns the qname of the attribute at the provided index
String	getAttributeNamespace(int index)	Returns the namespace of the attribute at the provided index
String	getAttributePrefix(int index)	Returns the prefix of this attribute at the provided index
String	getAttributeType(int index)	Returns the XML type of the attribute at the provided index
String	getAttributeValue(int index)	Returns the value of the attribute at the index
String	getAttributeValue(String namespaceURI, String localName)	Returns the normalized attribute value of the attribute with the namespace and localName If the namespaceURI is null the namespace is not checked for equality
String	getCharacterEncodingScheme()	Returns the character encoding declared on the xml declaration Returns null if none was declared
String	getElementText()	Reads the content of a text-only element, an exception is thrown if this is not a text-only element.
String	getEncoding()	Return input encoding if known or null if unknown.
int	getEventType()	Returns an integer code that indicates the type of the event the cursor is pointing to.
String	getLocalName()	Returns the (local) name of the current event.
Location	getLocation()	Return the current location of the processor.
QName	getName()	Returns a QName for the current START_ELEMENT or END_ELEMENT event
NamespaceContext	getNamespaceContext()	Returns a read only namespace context for the current position.
int	getNamespaceCount()	Returns the count of namespaces declared on this START_ELEMENT or END_ELEMENT, this method is only valid on a START_ELEMENT, END_ELEMENT or NAMESPACE.
String	getNamespacePrefix(int index)	Returns the prefix for the namespace declared at the index.
String	getNamespaceURI()	If the current event is a START_ELEMENT or END_ELEMENT this method returns the URI of the prefix or the default namespace.
String	getNamespaceURI(int index)	Returns the uri for the namespace declared at the index.
String	getNamespaceURI(String prefix)	Return the uri for the given prefix.
String	getPIData()	Get the data section of a processing instruction
String	getPITarget()	Get the target of a processing instruction
String	getPrefix()	Returns the prefix of the current event or null if the event does not have a prefix
Object	getProperty(String name)	Get the value of a feature/property from the underlying implementation
String	getText()	Returns the current value of the parse event as a string, this returns the string value of a CHARACTERS event, returns the value of a COMMENT, the replacement value for an ENTITY_REFERENCE, the string value of a CDATA section, the string value for a SPACE event, or the String value of the internal subset of the DTD.
char[]	getTextCharacters()	Returns an array which contains the characters from this event.
int	getTextCharacters(int sourceStart, char[] target, int targetStart, int length)	Gets the the text associated with a CHARACTERS, SPACE or CDATA event.
int	getTextLength()	Returns the length of the sequence of characters for this Text event within the text character array.
int	getTextStart()	Returns the offset into the text character array where the first character (of this text event) is stored.
String	getVersion()	Get the xml version declared on the xml declaration Returns null if none was declared
boolean	hasName()	returns a boolean indicating whether the current event has a name (is a START_ELEMENT or END_ELEMENT).
boolean	hasNext()	Returns true if there are more parsing events and false if there are no more events.
boolean	hasText()	Return a boolean indicating whether the current event has text.
boolean	isAttributeSpecified(int index)	Returns a boolean which indicates if this attribute was created by default
boolean	isCharacters()	Returns true if the cursor points to a character data event
boolean	isEndElement()	Returns true if the cursor points to an end tag (otherwise false)
boolean	isStandalone()	Get the standalone declaration from the xml declaration
boolean	isStartElement()	Returns true if the cursor points to a start tag (otherwise false)
boolean	isWhiteSpace()	Returns true if the cursor points to a character data event that consists of all whitespace
int	next()	Get next parsing event - a processor may return all contiguous character data in a single chunk, or it may split it into several chunks.
int	nextTag()	Skips any white space (isWhiteSpace() returns true), COMMENT, or PROCESSING_INSTRUCTION, until a START_ELEMENT or END_ELEMENT is reached.
void	require(int type, String namespaceURI, String localName)	Test if the current event is of the given type and if the namespace and name match the current namespace and name of the current event.
boolean	standaloneSet()	Checks if standalone was set in the document

Method Details

getProperty

Object getProperty(String name) throws IllegalArgumentException

Get the value of a feature/property from the underlying implementation

Parameters:

name - The name of the property, may not be null

Returns:

The value of the property

Throws:

IllegalArgumentException - if name is null

next

int next() throws XMLStreamException

Get next parsing event - a processor may return all contiguous character data in a single chunk, or it may split it into several chunks. If the property javax.xml.stream.isCoalescing is set to true element content must be coalesced and only one CHARACTERS event must be returned for contiguous element content or CDATA Sections. By default entity references must be expanded and reported transparently to the application. An exception will be thrown if an entity reference cannot be expanded. If element content is empty (i.e. content is "") then no CHARACTERS event will be reported.

Given the following XML:
<foo><!--description-->content text<![CDATA[<greeting>Hello>/greeting>]]>other content>/foo>
The behavior of calling next() when being on foo will be:
1- the comment (COMMENT)
2- then the characters section (CHARACTERS)
3- then the CDATA section (another CHARACTERS)
4- then the next characters section (another CHARACTERS)
5- then the END_ELEMENT

NOTE: empty element (such as <tag/>) will be reported with two separate events: START_ELEMENT, END_ELEMENT - This preserves parsing equivalency of empty element to <tag></tag>.

Returns:

the integer code corresponding to the current parse event

Throws:

NoSuchElementException - if this is called when hasNext() returns false

XMLStreamException - if there is an error processing the underlying XML source

See Also:

XMLEvent

require

void require(int type, String namespaceURI, String localName) throws XMLStreamException

Test if the current event is of the given type and if the namespace and name match the current namespace and name of the current event. If the namespaceURI is null it is not checked for equality, if the localName is null it is not checked for equality.

Parameters:

type - the event type

namespaceURI - the uri of the event, may be null

localName - the localName of the event, may be null

Throws:

XMLStreamException - if the required values are not matched.

getElementText

String getElementText() throws XMLStreamException

Reads the content of a text-only element, an exception is thrown if this is not a text-only element. Regardless of value of javax.xml.stream.isCoalescing this method always returns coalesced content.
Precondition: the current event is START_ELEMENT.
Postcondition: the current event is the corresponding END_ELEMENT.
The method does the following (implementations are free to optimized but must do equivalent processing):

 if(getEventType() != XMLStreamConstants.START_ELEMENT) {
     throw new XMLStreamException(
     "parser must be on START_ELEMENT to read next text", getLocation());
 }

 int eventType = next();
 StringBuffer content = new StringBuffer();
 while(eventType != XMLStreamConstants.END_ELEMENT) {
     if(eventType == XMLStreamConstants.CHARACTERS
        || eventType == XMLStreamConstants.CDATA
        || eventType == XMLStreamConstants.SPACE
        || eventType == XMLStreamConstants.ENTITY_REFERENCE) {
           buf.append(getText());
     } else if(eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
               || eventType == XMLStreamConstants.COMMENT) {
         // skipping
     } else if(eventType == XMLStreamConstants.END_DOCUMENT) {
         throw new XMLStreamException(
         "unexpected end of document when reading element text content", this);
     } else if(eventType == XMLStreamConstants.START_ELEMENT) {
         throw new XMLStreamException(
         "element text content may not contain START_ELEMENT", getLocation());
     } else {
         throw new XMLStreamException(
         "Unexpected event type "+eventType, getLocation());
     }
     eventType = next();
 }
 return buf.toString();
 

Throws:

XMLStreamException - if the current event is not a START_ELEMENT or if a non text element is encountered

nextTag

int nextTag() throws XMLStreamException

Skips any white space (isWhiteSpace() returns true), COMMENT, or PROCESSING_INSTRUCTION, until a START_ELEMENT or END_ELEMENT is reached. If other than white space characters, COMMENT, PROCESSING_INSTRUCTION, START_ELEMENT, END_ELEMENT are encountered, an exception is thrown. This method should be used when processing element-only content seperated by white space.
Precondition: none
Postcondition: the current event is START_ELEMENT or END_ELEMENT and cursor may have moved over any whitespace event.
Essentially it does the following (implementations are free to optimized but must do equivalent processing):

 
 int eventType = next();
 while((eventType == XMLStreamConstants.CHARACTERS && isWhiteSpace()) // skip whitespace
 || (eventType == XMLStreamConstants.CDATA && isWhiteSpace())
 // skip whitespace
 || eventType == XMLStreamConstants.SPACE
 || eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
 || eventType == XMLStreamConstants.COMMENT
 ) {
     eventType = next();
 }
 if (eventType != XMLStreamConstants.START_ELEMENT && eventType != XMLStreamConstants.END_ELEMENT) {
     throw new String XMLStreamException("expected start or end tag", getLocation());
 }
 return eventType; 
 

Returns:

the event type of the element read (START_ELEMENT or END_ELEMENT)

Throws:

XMLStreamException - if the current event is not white space, PROCESSING_INSTRUCTION, START_ELEMENT or END_ELEMENT

NoSuchElementException - if this is called when hasNext() returns false

hasNext

boolean hasNext() throws XMLStreamException

Returns true if there are more parsing events and false if there are no more events. This method will return false if the current state of the XMLStreamReader is END_DOCUMENT

Returns:

true if there are more events, false otherwise

Throws:

XMLStreamException - if there is a fatal error detecting the next state

close

void close() throws XMLStreamException

Frees any resources associated with this Reader. This method does not close the underlying input source.

Throws:

XMLStreamException - if there are errors freeing associated resources

getNamespaceURI

String getNamespaceURI(String prefix)

Return the uri for the given prefix. The uri returned depends on the current state of the processor.

NOTE:The 'xml' prefix is bound as defined in Namespaces in XML specification to "http://www.w3.org/XML/1998/namespace".

NOTE: The 'xmlns' prefix must be resolved to following namespace http://www.w3.org/2000/xmlns/

Parameters:

prefix - The prefix to lookup, may not be null

Returns:

the uri bound to the given prefix or null if it is not bound

Throws:

IllegalArgumentException - if the prefix is null

isStartElement

boolean isStartElement()

Returns true if the cursor points to a start tag (otherwise false)

Returns:

true if the cursor points to a start tag, false otherwise

isEndElement

boolean isEndElement()

Returns true if the cursor points to an end tag (otherwise false)

Returns:

true if the cursor points to an end tag, false otherwise

isCharacters

boolean isCharacters()

Returns true if the cursor points to a character data event

Returns:

true if the cursor points to character data, false otherwise

isWhiteSpace

boolean isWhiteSpace()

Returns true if the cursor points to a character data event that consists of all whitespace

Returns:

true if the cursor points to all whitespace, false otherwise

getAttributeValue

String getAttributeValue(String namespaceURI, String localName)

Returns the normalized attribute value of the attribute with the namespace and localName If the namespaceURI is null the namespace is not checked for equality

Parameters:

namespaceURI - the namespace of the attribute

localName - the local name of the attribute, cannot be null

Returns:

returns the value of the attribute , returns null if not found

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributeCount

int getAttributeCount()

Returns the count of attributes on this START_ELEMENT, this method is only valid on a START_ELEMENT or ATTRIBUTE. This count excludes namespace definitions. Attribute indices are zero-based.

Returns:

returns the number of attributes

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributeName

QName getAttributeName(int index)

Returns the qname of the attribute at the provided index

Parameters:

index - the position of the attribute

Returns:

the QName of the attribute

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributeNamespace

String getAttributeNamespace(int index)

Returns the namespace of the attribute at the provided index

Parameters:

index - the position of the attribute

Returns:

the namespace URI (can be null)

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributeLocalName

String getAttributeLocalName(int index)

Returns the localName of the attribute at the provided index

Parameters:

index - the position of the attribute

Returns:

the localName of the attribute

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributePrefix

String getAttributePrefix(int index)

Returns the prefix of this attribute at the provided index

Parameters:

index - the position of the attribute

Returns:

the prefix of the attribute

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributeType

String getAttributeType(int index)

Returns the XML type of the attribute at the provided index

Parameters:

index - the position of the attribute

Returns:

the XML type of the attribute

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getAttributeValue

String getAttributeValue(int index)

Returns the value of the attribute at the index

Parameters:

index - the position of the attribute

Returns:

the attribute value

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

isAttributeSpecified

boolean isAttributeSpecified(int index)

Returns a boolean which indicates if this attribute was created by default

Parameters:

index - the position of the attribute

Returns:

true if this is a default attribute

Throws:

IllegalStateException - if this is not a START_ELEMENT or ATTRIBUTE

getNamespaceCount

int getNamespaceCount()

Returns the count of namespaces declared on this START_ELEMENT or END_ELEMENT, this method is only valid on a START_ELEMENT, END_ELEMENT or NAMESPACE. On an END_ELEMENT the count is of the namespaces that are about to go out of scope. This is the equivalent of the information reported by SAX callback for an end element event.

Returns:

returns the number of namespace declarations on this specific element

Throws:

IllegalStateException - if this is not a START_ELEMENT, END_ELEMENT or NAMESPACE

getNamespacePrefix

String getNamespacePrefix(int index)

Returns the prefix for the namespace declared at the index. Returns null if this is the default namespace declaration

Parameters:

index - the position of the namespace declaration

Returns:

returns the namespace prefix

Throws:

IllegalStateException - if this is not a START_ELEMENT, END_ELEMENT or NAMESPACE

getNamespaceURI

String getNamespaceURI(int index)

Returns the uri for the namespace declared at the index.

Parameters:

index - the position of the namespace declaration

Returns:

returns the namespace uri

Throws:

IllegalStateException - if this is not a START_ELEMENT, END_ELEMENT or NAMESPACE

getNamespaceContext

NamespaceContext getNamespaceContext()

Returns a read only namespace context for the current position. The context is transient and only valid until a call to next() changes the state of the reader.

Returns:

return a namespace context

getEventType

int getEventType()

Returns an integer code that indicates the type of the event the cursor is pointing to. The initial event type is XMLStreamConstants.START_DOCUMENT.

Returns:

the type of the current event

getText

String getText()

Returns the current value of the parse event as a string, this returns the string value of a CHARACTERS event, returns the value of a COMMENT, the replacement value for an ENTITY_REFERENCE, the string value of a CDATA section, the string value for a SPACE event, or the String value of the internal subset of the DTD. If an ENTITY_REFERENCE has been resolved, any character data will be reported as CHARACTERS events.

Returns:

the current text or null

Throws:

IllegalStateException - if this state is not a valid text state.

getTextCharacters

char[] getTextCharacters()

Returns an array which contains the characters from this event. This array should be treated as read-only and transient. I.e. the array will contain the text characters until the XMLStreamReader moves on to the next event. Attempts to hold onto the character array beyond that time or modify the contents of the array are breaches of the contract for this interface.

Returns:

the current text or an empty array

Throws:

IllegalStateException - if this state is not a valid text state.

getTextCharacters

int getTextCharacters(int sourceStart, char[] target, int targetStart, int length) throws XMLStreamException

Gets the the text associated with a CHARACTERS, SPACE or CDATA event. Text starting a "sourceStart" is copied into "target" starting at "targetStart". Up to "length" characters are copied. The number of characters actually copied is returned. The "sourceStart" argument must be greater or equal to 0 and less than or equal to the number of characters associated with the event. Usually, one requests text starting at a "sourceStart" of 0. If the number of characters actually copied is less than the "length", then there is no more text. Otherwise, subsequent calls need to be made until all text has been retrieved. For example:

 int length = 1024;
 char[] myBuffer = new char[ length ];

 for ( int sourceStart = 0 ; ; sourceStart += length )
 {
    int nCopied = stream.getTextCharacters( sourceStart, myBuffer, 0, length );

   if (nCopied < length)
       break;
 }
  

XMLStreamException may be thrown if there are any XML errors in the underlying source. The "targetStart" argument must be greater than or equal to 0 and less than the length of "target", Length must be greater than 0 and "targetStart + length" must be less than or equal to length of "target".

Parameters:

sourceStart - the index of the first character in the source array to copy

target - the destination array

targetStart - the start offset in the target array

length - the number of characters to copy

Returns:

the number of characters actually copied

Throws:

XMLStreamException - if the underlying XML source is not well-formed

IndexOutOfBoundsException - if targetStart < 0 or > than the length of target

IndexOutOfBoundsException - if length < 0 or targetStart + length > length of target

UnsupportedOperationException - if this method is not supported

NullPointerException - is if target is null

getTextStart

int getTextStart()

Returns the offset into the text character array where the first character (of this text event) is stored.

Returns:

the starting position of the text in the character array

Throws:

IllegalStateException - if this state is not a valid text state.

getTextLength

int getTextLength()

Returns the length of the sequence of characters for this Text event within the text character array.

Returns:

the length of the text

Throws:

IllegalStateException - if this state is not a valid text state.

getEncoding

String getEncoding()

Return input encoding if known or null if unknown.

Returns:

the encoding of this instance or null

hasText

boolean hasText()

Return a boolean indicating whether the current event has text. The following events have text: CHARACTERS,DTD ,ENTITY_REFERENCE, COMMENT, SPACE

Returns:

true if the event has text, false otherwise

getLocation

Location getLocation()

Return the current location of the processor. If the Location is unknown the processor should return an implementation of Location that returns -1 for the location and null for the publicId and systemId. The location information is only valid until next() is called.

Returns:

the location of the cursor

getName

QName getName()

Returns a QName for the current START_ELEMENT or END_ELEMENT event

Returns:

the QName for the current START_ELEMENT or END_ELEMENT event

Throws:

IllegalStateException - if this is not a START_ELEMENT or END_ELEMENT

getLocalName

String getLocalName()

Returns the (local) name of the current event. For START_ELEMENT or END_ELEMENT returns the (local) name of the current element. For ENTITY_REFERENCE it returns entity name. The current event must be START_ELEMENT or END_ELEMENT, or ENTITY_REFERENCE

Returns:

the localName

Throws:

IllegalStateException - if this not a START_ELEMENT, END_ELEMENT or ENTITY_REFERENCE

hasName

boolean hasName()

returns a boolean indicating whether the current event has a name (is a START_ELEMENT or END_ELEMENT).

Returns:

true if the event has a name, false otherwise

getNamespaceURI

String getNamespaceURI()

If the current event is a START_ELEMENT or END_ELEMENT this method returns the URI of the prefix or the default namespace. Returns null if the event does not have a prefix.

Returns:

the URI bound to this elements prefix, the default namespace, or null

getPrefix

String getPrefix()

Returns the prefix of the current event or null if the event does not have a prefix

Returns:

the prefix or null

getVersion

String getVersion()

Get the xml version declared on the xml declaration Returns null if none was declared

Returns:

the XML version or null

isStandalone

boolean isStandalone()

Get the standalone declaration from the xml declaration

Returns:

true if this is standalone, or false otherwise

standaloneSet

boolean standaloneSet()

Checks if standalone was set in the document

Returns:

true if standalone was set in the document, or false otherwise

getCharacterEncodingScheme

String getCharacterEncodingScheme()

Returns the character encoding declared on the xml declaration Returns null if none was declared

Returns:

the encoding declared in the document or null

getPITarget

String getPITarget()

Get the target of a processing instruction

Returns:

the target or null

getPIData

String getPIData()

Get the data section of a processing instruction

Returns:

the data or null