Package net.sf.saxon.s9api

Class XdmValue

java.lang.Object
net.sf.saxon.s9api.XdmValue
All Implemented Interfaces:
Iterable<XdmItem>
Direct Known Subclasses:
XdmEmptySequence, XdmItem
public class XdmValue extends Object implements Iterable<XdmItem>
A value in the XDM data model. A value is a sequence of zero or more items, each item being an atomic value, a node, or a function item.

An XdmValue is immutable.

A sequence consisting of a single item may be represented as an instance of XdmItem, which is a subtype of XdmValue. However, there is no guarantee that a sequence of length one will always be an instance of XdmItem.

Similarly, a zero-length sequence may be represented as an instance of XdmEmptySequence, but there is no guarantee that every sequence of length zero will always be an instance of XdmEmptySequence.

Since:
9.0

  • Constructor Details

    • XdmValue

      protected XdmValue(GroundedValue value)
      Create an XdmValue that wraps a supplied GroundedValue. This method is primarily for internal use, though it is also available to applications that manipulate data using lower-level Saxon interfaces.

      Note that this constructor necessarily produces an XdmValue regardless of the supplied value. To construct instances of subclasses of XdmValue, such as XdmAtomicValue or XdmNode, use the wrap(net.sf.saxon.om.Sequence) method, or use the overriding constructor on the required subclass.

      Parameters:
      value - the value to be wrapped.

    • XdmValue

      public XdmValue(Iterable<? extends XdmItem> items)
      Create an XdmValue as a sequence of XdmItem objects
      Parameters:
      items - a sequence of XdmItem objects. Note that if this is supplied as a list or similar collection, subsequent changes to the list/collection will have no effect on the XdmValue.
      Since:
      9.0.0.4

    • XdmValue

      public XdmValue(Iterator<? extends XdmItem> iterator) throws SaxonApiException
      Create an XdmValue containing the items returned by an Iterator.
      Parameters:
      iterator - the iterator that supplies the values
      Throws:
      SaxonApiException - if an error occurs reading values from the supplied iterator
      Since:
      9.6. Extended in 9.9 to take any Iterator, not just an XdmSequenceIterator.

    • XdmValue

      public XdmValue(Stream<? extends XdmItem> stream) throws SaxonApiException
      Create an XdmValue containing the results of reading a Stream
      Parameters:
      stream - the stream to be read
      Throws:
      SaxonApiException - if an error occurs reading values from the supplied stream

  • Method Details

    • wrap

      public static XdmValue wrap(Sequence value)
      Create an XdmValue that wraps an existing Saxon Sequence
      Parameters:
      value - the supplied Sequence (which may be a singleton Item),
      Returns:
      an XdmValue corresponding to the supplied Sequence. If the supplied value is null, an empty sequence is returned. If the supplied value is an atomic value, the result will be an instance of XdmAtomicValue.
      • If the supplied value is a node, the result will be an instance of XdmNode.
      • If the supplied value is a map, the result will be an instance of XdmMap.
      • If the supplied value is an array, the result will be an instance of XdmArray.
      • If the supplied value is a function item, the result will be an instance of XdmFunctionItem.
      Throws:
      SaxonApiUncheckedException - if the supplied Sequence is not yet fully evaluated, and evaluation of the underlying expression fails with a dynamic error.
      Since:
      9.5 (previously a protected method)

    • wrap

      public static XdmValue wrap(AtomicSequence value)

    • append

      public XdmValue append(XdmValue otherValue)
      Create a new XdmValue by concatenating the contents of this XdmValue and another XdmValue into a single sequence. The two input XdmValue objects are unaffected by this operation.

      Note: creating a sequence of N values by successive calls on this method takes time proportional to N-squared.

      Parameters:
      otherValue - the value to be appended
      Returns:
      a new XdmValue containing the concatenation of the two input XdmValue objects
      Since:
      9.2

    • size

      public int size()
      Get the number of items in the sequence
      Returns:
      the number of items in the value, considered as a sequence. Note that for arrays and maps, the answer will be 1 (one) since arrays and maps are items.

    • isEmpty

      public boolean isEmpty()
      Ask whether the sequence is empty
      Returns:
      true if the value is an empty sequence
      Since:
      10.1

    • itemAt

      public XdmItem itemAt(int n) throws IndexOutOfBoundsException, SaxonApiUncheckedException
      Get the n'th item in the value, counting from zero.
      Parameters:
      n - the item that is required, counting the first item in the sequence as item zero
      Returns:
      the n'th item in the sequence making up the value, counting from zero
      Throws:
      IndexOutOfBoundsException - if n is less than zero or greater than or equal to the number of items in the value
      SaxonApiUncheckedException - if the value is lazily evaluated and the delayed evaluation fails with a dynamic error.

    • subsequence

      public XdmValue subsequence(int start, int length)
      Get a subsequence of the value
      Parameters:
      start - the index of the first item to be included in the result, counting from zero. A negative value is taken as zero. If the value is beyond the end of the sequence, an empty sequence is returned
      length - the number of items to be included in the result. Specify Integer.MAX_VALUE to get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence is returned. If the length goes off the end of the sequence, the result returns items up to the end of the sequence
      Returns:
      the required subsequence.
      Since:
      11

    • iterator

      public XdmSequenceIterator<XdmItem> iterator() throws SaxonApiUncheckedException
      Get an iterator over the items in this value.
      Specified by:
      iterator in interface Iterable<XdmItem>
      Returns:
      an Iterator over the items in this value.
      Throws:
      SaxonApiUncheckedException - if the value is lazily evaluated and the delayed evaluation fails with a dynamic error.

    • getUnderlyingValue

      public GroundedValue getUnderlyingValue()
      Get the underlying implementation object representing the value. This method allows access to lower-level Saxon functionality, including classes and methods that offer no guarantee of stability across releases.
      Returns:
      the underlying implementation object representing the value

    • toString

      public String toString()
      Create a string representation of the value. This is the result of serializing the value using the adaptive serialization method, with the options indent="yes" and omit-xml-declaration="yes". The item-separator if there are multiple items is a newline. Any trailing newline in the result is removed.

      Note that this method does not return the same result as the XPath fn:string() function: it corresponds more closely to the fn:serialize() function.

      If the XdmValue is an element node, the result will be a well-formed XML document serialized as defined in the W3C XSLT/XQuery serialization specification, using options method="xml", indent="yes", omit-xml-declaration="yes".

      In the case of a document node, the result will be a well-formed XML document provided that the document node contains exactly one element child, and no text node children.

      In the case of an attribute node, the output is a string in the form name="value". The name will use the original namespace prefix.

      In the case of a namespace node, the output is a string in the form of a namespace declaration, that is xmlns="uri" or xmlns:pre="uri".

      Other nodes, such as text nodes, comments, and processing instructions, are represented as they would appear in lexical XML. Note: this means that in the case of text nodes, special characters such as & and < are output in escaped form. To get the unescaped string value of a text node, use XdmItem.getStringValue() instead.

      Atomic values are serialized according to the rules of the adaptive output method, for example true(), "blue", 42, or xs:date("2023-01-31").

      A sequence of items is formatted by serializing the individual items, separated by newlines.

      Overrides:
      toString in class Object
      Returns:
      a string representation of the value

    • makeSequence

      public static XdmValue makeSequence(Iterable<?> list) throws IllegalArgumentException
      Make an XDM sequence from a Java Iterable. Each value delivered by the iterable is first converted to an XDM value using the makeValue(Object) method; if the result is anything other than a single XDM item, it is then wrapped in an XdmArray.
      Parameters:
      list - the Java iterable
      Returns:
      the result of the conversion if successful
      Throws:
      IllegalArgumentException - if conversion is not possible

    • makeValue

      public static XdmValue makeValue(Object o) throws IllegalArgumentException
      Make an XDM value from a Java object. The supplied object may be any of the following:
      Parameters:
      o - the Java object
      Returns:
      the result of the conversion if successful
      Throws:
      IllegalArgumentException - if conversion is not possible

    • documentOrder

      public XdmValue documentOrder() throws SaxonApiException
      Return a new XdmValue containing the nodes present in this XdmValue, with duplicates eliminated, and sorted into document order
      Returns:
      the same nodes, sorted into document order, with duplicates eliminated
      Throws:
      SaxonApiException - if anything goes wrong (typically during delayed evaluation of the input sequence)
      ClassCastException - if the sequence contains items that are not nodes
      Since:
      9.9

    • stream

      public XdmStream<? extends XdmItem> stream()
      Get a stream comprising the items in this value
      Returns:
      a Stream over the items in this value
      Since:
      9.9

    • select

      public <T extends XdmItem> XdmStream<T> select(Step<T> step)
      Get a stream of items by applying a Step to the items in this value. This operation is analogous to the Stream.flatMap operation in Java, or to the "!" operator in XPath.

      The following examples assume a static import declaration of the standard Steps: import static net.sf.saxon.s9api.streams.Steps.*;

      • select(child()) returns a stream containing all children
      • select(child("*")) returns a stream containing all element children
      • select(child("author")) returns a stream containing all element children with local name "author" (regardless of namespace)
      • select(child("http://my.ns/", "author")) returns a stream containing all element children with local name "author" and namespace "http://my.ns/"
      • select(descendant("author")) returns a stream containing all element descendants with local name "author" (regardless of namespace)
      • select(descendant("author").then(attribute("name")) returns a stream containing the "name" attributes of "author" descendants
      • select(path("//", "author", "@name")) returns a stream containing the "name" attributes of "author" descendants
      • select(child("author").where(attributeEq("firstName", "Jane")) returns a stream containing all the "author" children having a "firstName" attribute whose value is "Jane"
      • select(child("author").first()) returns a stream containing the first "author" child (if there is one)
      • select(child("author").where(attributeEq("firstName", "Jane").last()) returns a stream containing the last "author" child having a "firstName" attribute whose value is "Jane" (if there is one)

      In each of the above examples, the selected nodes are returned as an XdmStream<XdmNode>; this class extends Stream<XdmNode>, so all the standard operations on streams are available, together with some additional operations specific to node streams.

      The select method thus has comparable power to simple XPath expressions; but unlike XPath expressions, there is no run-time overhead in parsing the XPath expression and developing an execution plan.

      Type Parameters:
      T - the type of items to be returned by the step (often XdmNode)
      Parameters:
      step - the Step to be applied to the items in this value. This will often be one of the standard steps returned by the static methods of the Steps class, such as Steps.child(), or by instance methods (such as Step.where(java.util.function.Predicate<? super T>), Step.cat(net.sf.saxon.s9api.streams.Step<T>), or Step.first()) but it is also possible to create user-defined steps.
      Returns:
      a Stream of items obtained by replacing each item X in this value by the items obtained by applying the Step function to X.
      Since:
      9.9

    • where

      public XdmValue where(Predicate<? super XdmItem> predicate)
      Filter the value on a supplied predicate
      Parameters:
      predicate - the predicate to be applied. Note that an ItemType is a predicate, so this method can be used to select those items that match a supplied item type. For example, where(ItemType.INTEGER) will select the items in the sequence that are instances of xs:integer.
      Returns:
      a new XdmValue comprising those items in this XdmValue that match the given predicate.
      Since:
      12.0

    • matches

      public boolean matches(SequenceType type)
      Test whether the value matches a supplied SequenceType
      Parameters:
      type - the SequenceType that we are testing against
      Returns:
      true if this value matches the sequence type, false otherwise.
      Since:
      12.0