Class CastableExpression

  • All Implemented Interfaces:
    java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, org.xml.sax.Locator

    public final class CastableExpression
    extends CastingExpression
    Castable Expression: implements "Expr castable as atomic-type?". The implementation simply wraps a cast expression with a try/catch.
    See Also:
    Serialized Form
    • Constructor Detail

      • CastableExpression

        public CastableExpression​(Expression source,
                                  AtomicType target,
                                  boolean allowEmpty)
        Create a "castable" expression of the form "source castable as target"
        Parameters:
        source - The source expression
        target - The type being tested against
        allowEmpty - true if an empty sequence is acceptable, that is if the expression was written as "source castable as target?"
    • Method Detail

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                                    ExpressionVisitor.ContextItemType contextItemType)
                             throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class UnaryExpression
        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,
                                   ExpressionVisitor.ContextItemType contextItemType)
                            throws XPathException
        Optimize the expression
        Overrides:
        optimize in class UnaryExpression
        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)
      • equals

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

        public int hashCode()
        get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.
        Overrides:
        hashCode in class UnaryExpression
      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Determine the data type of the result of the Castable expression
        Overrides:
        getItemType in class UnaryExpression
        Parameters:
        th - the type hierarchy cache
        Returns:
        the item type of the items in the result sequence, insofar as this is known statically.
      • copy

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

        public Item evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate the expression
        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
      • effectiveBooleanValue

        public boolean effectiveBooleanValue​(XPathContext context)
                                      throws XPathException
        Description copied from class: Expression
        Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.
        Overrides:
        effectiveBooleanValue in class Expression
        Parameters:
        context - The context in which the expression is to be evaluated
        Returns:
        the effective boolean value
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
      • toString

        public java.lang.String toString()
        The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
        Overrides:
        toString in class UnaryExpression
        Returns:
        a representation of the expression as a string
      • explain

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