Package net.sf.saxon.expr.instruct

Class DocumentInstr

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.instruct.Instruction
net.sf.saxon.expr.instruct.ParentNodeConstructor
net.sf.saxon.expr.instruct.DocumentInstr
All Implemented Interfaces:
ExportAgent, InstructionWithComplexContent, ValidatingInstruction, Locatable, IdentityComparable, Traceable
public class DocumentInstr extends ParentNodeConstructor
An instruction to create a document node. This corresponds to the xsl:document-node instruction in XSLT. It is also used to support the document node constructor expression in XQuery, and is generated implicitly within an xsl:variable that constructs a temporary tree.

Conceptually it represents an XSLT instruction xsl:document-node, with no attributes, whose content is a complex content constructor for the children of the document node.

  • Constructor Details

    • DocumentInstr

      public DocumentInstr(boolean textOnly, UnicodeString constantText)
      Create a document constructor instruction
      Parameters:
      textOnly - true if the content contains text nodes only
      constantText - if the content contains text nodes only and the text is known at compile time, supplies the textual content

  • Method Details

    • operands

      public Iterable<Operand> operands()
      Description copied from class: Expression
      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

      If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

      Specified by:
      operands in class Instruction
      Returns:
      an iterator containing the sub-expressions of this expression

    • getImplementationMethod

      public int getImplementationMethod()
      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered. For instructions this is the process() method.
      Overrides:
      getImplementationMethod in class Instruction
      Returns:
      the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

    • isTextOnly

      public boolean isTextOnly()
      Determine whether this is a "text only" document: essentially, an XSLT xsl:variable that contains a single text node or xsl:value-of instruction.
      Returns:
      true if this is a text-only document

    • getConstantText

      public UnicodeString getConstantText()
      For a text-only instruction, determine if the text value is fixed and if so return it; otherwise return null
      Returns:
      the fixed text value if appropriate; otherwise null

    • checkContentSequence

      protected void checkContentSequence(StaticContext env) throws XPathException
      Check statically that the sequence of child instructions doesn't violate any obvious constraints on the content of the node
      Specified by:
      checkContentSequence in class ParentNodeConstructor
      Parameters:
      env - the static context
      Throws:
      XPathException - if the check fails

    • checkContentSequence

      protected static void checkContentSequence(StaticContext env, Operand content, ParseOptions validationOptions) throws XPathException
      Throws:
      XPathException

    • computeSpecialProperties

      protected int computeSpecialProperties()
      Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
      Overrides:
      computeSpecialProperties in class Instruction
      Returns:
      a set of flags indicating static properties of this expression

    • getStringValueExpression

      public Expression getStringValueExpression()
      In the case of a text-only instruction (xsl:variable containing a text node or one or more xsl:value-of instructions), return an expression that evaluates to the textual content as an instance of xs:untypedAtomic
      Returns:
      an expression that evaluates to the textual content

    • copy

      public Expression copy(RebindingMap rebindings)
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - the rebinding map
      Returns:
      the copy of the original expression

    • getItemType

      public ItemType getItemType()
      Get the item type
      Overrides:
      getItemType in class Instruction
      Returns:
      the in

    • evaluateItem

      public NodeInfo evaluateItem(XPathContext context) throws XPathException
      Evaluate as an item.
      Overrides:
      evaluateItem in class Instruction
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • getInstructionNameCode

      public int getInstructionNameCode()
      Get the name of this instruction for diagnostic and tracing purposes (the string "document-constructor")
      Overrides:
      getInstructionNameCode in class Instruction
      Returns:
      a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

    • export

      public void export(ExpressionPresenter out) throws XPathException
      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Specified by:
      export in interface ExportAgent
      Specified by:
      export in class Expression
      Parameters:
      out - the expression presenter used to display the structure
      Throws:
      XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

    • getStreamerName

      public String getStreamerName()
      Get the (partial) name of a class that supports streaming of this kind of expression
      Overrides:
      getStreamerName in class Expression
      Returns:
      the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class

    • getElaborator

      public Elaborator getElaborator()
      Description copied from class: Expression
      Make an elaborator for this expression
      Overrides:
      getElaborator in class Expression
      Returns:
      an appropriate Elaborator