Class KeyFn

All Implemented Interfaces:
Serializable, SourceLocator, Container, Expression, XSLTFunction, InstructionInfoProvider

public class KeyFn extends SystemFunction implements XSLTFunction
See Also:
  • Constructor Details

    • KeyFn

      public KeyFn()
  • Method Details

    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.
      Specified by:
      typeCheck in interface Expression
      Overrides:
      typeCheck in class FunctionCall
      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
    • internalKeyCall

      public static KeyFn internalKeyCall(NamePool pool, int fingerprint, String name, Expression value, Expression doc)
      Non-standard constructor to create an internal call on key() with a known key fingerprint
    • simplify

      public Expression simplify(StaticContext env) throws XPathException
      Simplify: add a third implicit argument, the context document
      Specified by:
      simplify in interface Expression
      Overrides:
      simplify in class FunctionCall
      Parameters:
      env - the static context
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • checkArguments

      public void checkArguments(StaticContext env) throws XPathException
      Description copied from class: SystemFunction
      Method called during static type checking
      Overrides:
      checkArguments in class SystemFunction
      Throws:
      XPathException
    • computeSpecialProperties

      public 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 a property bit is set, it is true, but if it is unset, the value is unknown.
      Overrides:
      computeSpecialProperties in class SystemFunction
    • preEvaluate

      public Expression preEvaluate(StaticContext env)
      preEvaluate: this method suppresses compile-time evaluation by doing nothing
      Overrides:
      preEvaluate in class FunctionCall
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Enumerate the results 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