Class ContextItemExpression

java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.ContextItemExpression
All Implemented Interfaces:
Serializable, SourceLocator, Container, Expression, InstructionInfoProvider
Direct Known Subclasses:
CurrentItemExpression

public class ContextItemExpression extends ComputedExpression
This class represents the expression "(dot)", which always returns the context item. This may be a AtomicValue or a Node.
See Also:
  • Field Details

  • Constructor Details

    • ContextItemExpression

      public ContextItemExpression()
  • Method Details

    • copy

      public ContextItemExpression copy()
      Create a clone copy of this expression
      Returns:
      a copy of this expression
    • getErrorCodeForUndefinedContext

      protected String getErrorCodeForUndefinedContext()
    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      Type-check the expression.
      Parameters:
      env - the static context of the expression
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
      XPathException
    • optimize

      public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
      Perform optimisation of an expression and its subexpressions.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      Parameters:
      opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
      env - the static context of the expression
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the original expression, rewritten if appropriate to optimize execution
      Throws:
      StaticError - if an error is discovered during this phase (typically a type error)
      XPathException
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the item type
      Parameters:
      th -
      Returns:
      a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)
    • computeCardinality

      public int computeCardinality()
      Get the static cardinality
      Specified by:
      computeCardinality in class ComputedExpression
    • computeSpecialProperties

      public int computeSpecialProperties()
      Determine the special properties of this expression
      Overrides:
      computeSpecialProperties in class ComputedExpression
      Returns:
      StaticProperty.NON_CREATIVE
    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class Object
    • hashCode

      public int hashCode()
      get HashCode for comparing two expressions
      Overrides:
      hashCode in class Object
    • getIntrinsicDependencies

      public int getIntrinsicDependencies()
      Description copied from class: ComputedExpression
      Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".
      Overrides:
      getIntrinsicDependencies in class ComputedExpression
      Returns:
      a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Iterate over the value of the expression
      Specified by:
      iterate in interface Expression
      Overrides:
      iterate in class ComputedExpression
      Parameters:
      context - supplies the context for evaluation
      Returns:
      a SequenceIterator that can be used to iterate over the result of the expression
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression
      Specified by:
      evaluateItem in interface Expression
      Overrides:
      evaluateItem in class ComputedExpression
      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
    • display

      public void display(int level, PrintStream out, Configuration config)
      Diagnostic print of expression structure
      Parameters:
      level - indentation level for this expression
      out - Output destination
      config -