IT. Expert System.

Java Standard Edition (SE)

XMLStreamReader


compact2, compact3
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();

    The next() method causes the reader to read the next parse event. The next() method returns an integer which identifies the type of event just read.

    The event type can be determined using getEventType().

    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
    Version:
    1.0
    See Also:
    XMLEvent, XMLInputFactory, XMLStreamWriter
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method and 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 true if the current event has a name (is a START_ELEMENT or END_ELEMENT) returns false otherwise
      boolean hasNext()
      Returns true if there are more parsing events and false if there are no more events.
      boolean hasText()
      Return true if the current event has text, false otherwise The following events have text: CHARACTERS,DTD ,ENTITY_REFERENCE, COMMENT, SPACE
      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 Detail

      • 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>. This method will throw an IllegalStateException if it is called after hasNext() returns false.

        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.
      • 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.
        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.
        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 true if the current event has text, false otherwise The following events have text: CHARACTERS,DTD ,ENTITY_REFERENCE, COMMENT, SPACE
      • 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.
      • 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 true if the current event has a name (is a START_ELEMENT or END_ELEMENT) returns 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


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