Module java.xml

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

  • 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