Class ErrorExpression

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.ErrorExpression
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

public class ErrorExpression extends Expression
Error expression: this expression is generated when the supplied expression cannot be parsed, and the containing element enables forwards-compatible processing. It defers the generation of an error message until an attempt is made to evaluate the expression
See Also:
  • Constructor Details

    • ErrorExpression

      public ErrorExpression(XPathException exception)
      Constructor
      Parameters:
      exception - the error found when parsing this expression
  • Method Details

    • getException

      public XPathException getException()
      Get the wrapped exception
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
      Type-check the expression.
      Overrides:
      typeCheck in class Expression
      Parameters:
      visitor - an expression visitor
      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 - if an error is discovered during this phase (typically a type error)
    • optimize

      public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
      Description copied from class: Expression
      Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

      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.

      Overrides:
      optimize in class Expression
      Parameters:
      visitor - an expression visitor
      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:
      XPathException - if an error is discovered during this phase (typically a type error)
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression. This always throws the exception registered when the expression was first parsed.
      Specified by:
      evaluateItem in interface EvaluableItem
      Overrides:
      evaluateItem in class Expression
      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
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Iterate over the expression. This always throws the exception registered when the expression was first parsed.
      Specified by:
      iterate in interface SequenceIterable
      Overrides:
      iterate in class Expression
      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
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the expression, if possible
      Specified by:
      getItemType in class Expression
      Parameters:
      th - the type hierarchy cache
      Returns:
      Type.ITEM (meaning not known in advance)
    • computeCardinality

      public int computeCardinality()
      Determine the static cardinality
      Specified by:
      computeCardinality in class Expression
      Returns:
      the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
    • copy

      public Expression copy()
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Returns:
      the copy of the original expression
    • explain

      public void explain(ExpressionPresenter destination)
      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Specified by:
      explain in class Expression
      Parameters:
      destination - the expression presenter used to display the structure