Class VirtualTreeWalker

  • All Implemented Interfaces:
    NamespaceDeclarations, PullProvider

    public class VirtualTreeWalker
    extends java.lang.Object
    implements PullProvider, NamespaceDeclarations
    A virtual tree walker provides a sequence of pull events describing the structure and content of a tree that is conceptually being constructed by expressions in a query or stylesheet; in fact the tree is not necessarily constructed in memory, and exists only as this stream of pull events.

    The tree is physically constructed if operations are requested that depend on the identity of the nodes in the tree, or that navigate within the tree. Operations such as copying or atomizing the tree can be done directly, without building it in memory. (Note however that if such operations are done more than once, the underlying instructions may be evaluated repeatedly.)

    • Constructor Detail

      • VirtualTreeWalker

        public VirtualTreeWalker​(ParentNodeConstructor instruction,
                                 XPathContext context)
        Create a VirtualTreeWalker to navigate the tree constructed by evaluating a given instruction in a given dyamic context
        Parameters:
        instruction - the instruction (this will always be an instruction that creates element or document nodes)
        context - the dynamic evaluation context
    • Method Detail

      • getNamePool

        public NamePool getNamePool()
        Get the namepool
      • current

        public int current()
        Get the event most recently returned by next(), or by other calls that change the position, for example getStringValue() and skipToMatchingEnd(). This method does not change the position of the PullProvider.
        Specified by:
        current in interface PullProvider
        Returns:
        the current event
      • getAttributes

        public AttributeCollection getAttributes()
                                          throws XPathException
        Get the attributes associated with the current element. This method must be called only after a START_ELEMENT event has been notified. The contents of the returned AttributeCollection are guaranteed to remain unchanged until the next START_ELEMENT event, but may be modified thereafter. The object should not be modified by the client.

        Attributes may be read before or after reading the namespaces of an element, but must not be read after the first child node has been read, or after calling one of the methods skipToEnd(), getStringValue(), or getTypedValue().

        Specified by:
        getAttributes in interface PullProvider
        Returns:
        an AttributeCollection representing the attributes of the element that has just been notified.
        Throws:
        XPathException
      • getNamespaceDeclarations

        public NamespaceDeclarations getNamespaceDeclarations()
                                                       throws XPathException
        Get the namespace declarations associated with the current element. This method must be called only after a START_ELEMENT event has been notified. In the case of a top-level START_ELEMENT event (that is, an element that either has no parent node, or whose parent is not included in the sequence being read), the NamespaceDeclarations object returned will contain a namespace declaration for each namespace that is in-scope for this element node. In the case of a non-top-level element, the NamespaceDeclarations will contain a set of namespace declarations and undeclarations, representing the differences between this element and its parent.

        It is permissible for this method to return namespace declarations that are redundant.

        The NamespaceDeclarations object is guaranteed to remain unchanged until the next START_ELEMENT event, but may then be overwritten. The object should not be modified by the client.

        Namespaces may be read before or after reading the attributes of an element, but must not be read after the first child node has been read, or after calling one of the methods skipToEnd(), getStringValue(), or getTypedValue().

        *
        Specified by:
        getNamespaceDeclarations in interface PullProvider
        Throws:
        XPathException
      • skipToMatchingEnd

        public int skipToMatchingEnd()
                              throws XPathException
        Skip the current subtree. This method may be called only immediately after a START_DOCUMENT or START_ELEMENT event. This call returns the matching END_DOCUMENT or END_ELEMENT event; the next call on next() will return the event following the END_DOCUMENT or END_ELEMENT.
        Specified by:
        skipToMatchingEnd in interface PullProvider
        Throws:
        java.lang.IllegalStateException - if the method is called at any time other than immediately after a START_DOCUMENT or START_ELEMENT event.
        XPathException
      • close

        public void close()
        Close the event reader. This indicates that no further events are required. It is not necessary to close an event reader after PullProvider.END_OF_INPUT has been reported, but it is recommended to close it if reading terminates prematurely. Once an event reader has been closed, the effect of further calls on next() is undefined.
        Specified by:
        close in interface PullProvider
      • setNameCode

        public void setNameCode​(int nameCode)
        Set the initial nameCode (the nameCode of the node at the root of the tree being walked)
      • getFingerprint

        public int getFingerprint()
        Get the fingerprint of the name of the element. This is similar to the nameCode, except that it does not contain any information about the prefix: so two elements with the same fingerprint have the same name, excluding prefix. This method can be used after the PullProvider.START_ELEMENT, PullProvider.END_ELEMENT, PullProvider.PROCESSING_INSTRUCTION, PullProvider.ATTRIBUTE, or PullProvider.NAMESPACE events. If called at other times, the result is undefined and may result in an IllegalStateException. If called when the current node is an unnamed namespace node (a node representing the default namespace) the returned value is -1.
        Specified by:
        getFingerprint in interface PullProvider
        Returns:
        the fingerprint. The fingerprint can be used to obtain the local name and namespace URI from the name pool.
      • getStringValue

        public java.lang.CharSequence getStringValue()
                                              throws XPathException
        Get the string value of the current element, text node, processing-instruction, or top-level attribute or namespace node, or atomic value.

        In other situations the result is undefined and may result in an IllegalStateException.

        If the most recent event was a PullProvider.START_ELEMENT, this method causes the content of the element to be read. The current event on completion of this method will be the corresponding PullProvider.END_ELEMENT. The next call of next() will return the event following the END_ELEMENT event.

        Specified by:
        getStringValue in interface PullProvider
        Returns:
        the String Value of the node in question, defined according to the rules in the XPath data model.
        Throws:
        XPathException
      • getAtomicValue

        public AtomicValue getAtomicValue()
        Get an atomic value. This call may be used only when the last event reported was ATOMIC_VALUE. This indicates that the PullProvider is reading a sequence that contains a free-standing atomic value; it is never used when reading the content of a node.
        Specified by:
        getAtomicValue in interface PullProvider
      • getTypeAnnotation

        public int getTypeAnnotation()
        Get the type annotation of the current attribute or element node, or atomic value. The result of this method is undefined unless the most recent event was START_ELEMENT, ATTRIBUTE, or ATOMIC_VALUE.
        Specified by:
        getTypeAnnotation in interface PullProvider
        Returns:
        the type annotation. This code is the fingerprint of a type name, which may be resolved to a SchemaType by access to the Configuration.
      • getSourceLocator

        public javax.xml.transform.SourceLocator getSourceLocator()
        Get the location of the current event. For an event stream representing a real document, the location information should identify the location in the lexical XML source. For a constructed document, it should identify the location in the query or stylesheet that caused the node to be created. A value of null can be returned if no location information is available.
        Specified by:
        getSourceLocator in interface PullProvider
      • getPrefix

        public java.lang.String getPrefix​(int index)
        Get the prefix of the n'th declaration (or undeclaration) in the list, counting from zero.
        Specified by:
        getPrefix in interface NamespaceDeclarations
        Parameters:
        index - the index identifying which declaration is required.
        Returns:
        the namespace prefix. For a declaration or undeclaration of the default namespace, this is the zero-length string.
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is out of range.
      • getURI

        public java.lang.String getURI​(int index)
        Get the namespace URI of the n'th declaration (or undeclaration) in the list, counting from zero.
        Specified by:
        getURI in interface NamespaceDeclarations
        Parameters:
        index - the index identifying which declaration is required.
        Returns:
        the namespace URI. For a namespace undeclaration, this is the zero-length string.
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is out of range.
      • getNamespaceCode

        public int getNamespaceCode​(int index)
        Get the n'th declaration in the list in the form of a namespace code. Namespace codes can be translated into a prefix and URI by means of methods in the NamePool
        Specified by:
        getNamespaceCode in interface NamespaceDeclarations
        Parameters:
        index - the index identifying which declaration is required.
        Returns:
        the namespace code. This is an integer whose upper half indicates the prefix (0 represents the default namespace), and whose lower half indicates the URI (0 represents an undeclaration).
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is out of range.
        See Also:
        NamePool.getPrefixFromNamespaceCode(int), NamePool.getURIFromNamespaceCode(int)
      • getNamespaceCodes

        public int[] getNamespaceCodes​(int[] buffer)
        Get all the namespace codes, as an array.
        Specified by:
        getNamespaceCodes in interface NamespaceDeclarations
        Parameters:
        buffer - a sacrificial array that the method is free to use to contain the result. May be null.
        Returns:
        an integer array containing namespace codes. The array may be filled completely with namespace codes, or it may be incompletely filled, in which case a -1 integer acts as a terminator.
      • getUnparsedEntities

        public java.util.List getUnparsedEntities()
        Get a list of unparsed entities.
        Specified by:
        getUnparsedEntities in interface PullProvider
        Returns:
        a list of unparsed entities, or null if the information is not available, or an empty list if there are no unparsed entities.