Class CastExpression

  • All Implemented Interfaces:
    java.io.Serializable, javax.xml.transform.SourceLocator, Container, Expression, InstructionInfoProvider

    public final class CastExpression
    extends UnaryExpression
    Cast Expression: implements "cast as data-type ( expression )". It also allows an internal cast, which has the same semantics as a user-requested cast, but maps an empty sequence to an empty sequence.
    See Also:
    Serialized Form
    • Constructor Detail

      • CastExpression

        public CastExpression​(Expression source,
                              AtomicType target,
                              boolean allowEmpty)
    • Method Detail

      • addAllowedCasts

        static void addAllowedCasts​(int source,
                                    int[] target)
      • isPossibleCast

        public static boolean isPossibleCast​(int source,
                                             int target)
        Determine whether casting from a source type to a target type is possible
        Parameters:
        source - a primitive type (one that has an entry in the casting table)
        target - another primitive type
        Returns:
        true if the entry in the casting table is either "Y" (casting always succeeds) or "M" (casting allowed but may fail for some values)
      • typeCheck

        public Expression typeCheck​(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException
        Type-check the expression
        Specified by:
        typeCheck in interface Expression
        Overrides:
        typeCheck in class UnaryExpression
        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:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException
      • 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
      • equals

        public boolean equals​(java.lang.Object other)
        Is this expression the same as another expression?
        Overrides:
        equals in class UnaryExpression
      • displayOperator

        protected java.lang.String displayOperator​(Configuration config)
        Give a string representation of the operator for use in diagnostics
        Specified by:
        displayOperator in class UnaryExpression
        Parameters:
        config -
        Returns:
        the operator, as a string
      • castStringToQName

        public static AtomicValue castStringToQName​(java.lang.CharSequence operand,
                                                    AtomicType targetType,
                                                    StaticContext env)
                                             throws XPathException
        Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value. This can only happen at compile time
        Returns:
        the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a DerivedAtomicValue derived from QName or NOTATION
        Throws:
        XPathException