Class ComputedElement

    • Constructor Detail

      • ComputedElement

        public ComputedElement​(Expression elementName,
                               Expression namespace,
                               NamespaceResolver nsContext,
                               SchemaType schemaType,
                               int validation,
                               boolean inheritNamespaces,
                               boolean allowQName)
        Create an instruction that creates a new element node
        Parameters:
        elementName - Expression that evaluates to produce the name of the element node as a lexical QName
        namespace - Expression that evaluates to produce the namespace URI of the element node. Set to null if the namespace is to be deduced from the prefix of the elementName.
        nsContext - Saved copy of the static namespace context for the instruction. Can be set to null if namespace is supplied. This namespace context must resolve the null prefix correctly, based on the different rules for XSLT and XQuery. //* @param defaultNamespace Default namespace to be used if no namespace is supplied and the //* computed element is a string with no prefix.
        validation - Required validation mode (e.g. STRICT, LAX, SKIP)
        inheritNamespaces - true if child elements automatically inherit the namespaces of their parent
        schemaType - The required schema type for the content
        allowQName - True if the elementName expression is allowed to return a QNameValue; false if it must return a string, and is cast to a string if necessary (that is, true in XQuery, false in XSLT).
    • Method Detail

      • getNameExpression

        public Expression getNameExpression()
        Get the expression used to compute the element name
        Returns:
        the expression used to compute the element name
      • getNamespaceExpression

        public Expression getNamespaceExpression()
        Get the expression used to compute the namespace URI
        Returns:
        the expression used to compute the namespace URI
      • getNamespaceResolver

        public NamespaceResolver getNamespaceResolver()
        Get the namespace resolver that provides the namespace bindings defined in the static context
        Returns:
        the namespace resolver
      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                                    ExpressionVisitor.ContextItemType contextItemType)
                             throws XPathException
        Description copied from class: Expression
        Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

        This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

        This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

        If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

        Overrides:
        typeCheck in class ParentNodeConstructor
        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
        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 ParentNodeConstructor
        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)
      • 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
      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Get the item type of the value returned by this instruction
        Overrides:
        getItemType in class ElementCreator
        Parameters:
        th - the type hierarchy cache
        Returns:
        the item type
      • replaceSubExpression

        public boolean replaceSubExpression​(Expression original,
                                            Expression replacement)
        Replace one subexpression by a replacement subexpression
        Overrides:
        replaceSubExpression in class ParentNodeConstructor
        Parameters:
        original - the original subexpression
        replacement - the replacement subexpression
        Returns:
        true if the original subexpression is found
      • promoteInst

        protected void promoteInst​(PromotionOffer offer)
                            throws XPathException
        Offer promotion for subexpressions. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.
        Overrides:
        promoteInst in class ParentNodeConstructor
        Parameters:
        offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
        Throws:
        XPathException - if any error is detected
      • checkPermittedContents

        public void checkPermittedContents​(SchemaType parentType,
                                           StaticContext env,
                                           boolean whole)
                                    throws XPathException
        Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
        Overrides:
        checkPermittedContents in class Expression
        Parameters:
        parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type
        env - the static context
        whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content
        Throws:
        XPathException - if the value delivered by this expression cannot be part of the content model of the given type
      • getElementName

        public NodeName getElementName​(XPathContext context,
                                       NodeInfo copiedNode)
                                throws XPathException
        Callback from the superclass ElementCreator to get the nameCode for the element name
        Specified by:
        getElementName in class ElementCreator
        Parameters:
        context - The evaluation context (not used)
        copiedNode - Not applicable to this overload
        Returns:
        the name code for the element name
        Throws:
        XPathException - if a failure occurs
      • isAllowNameAsQName

        public boolean isAllowNameAsQName()
        Ask whether the name can be supplied as a QName. In practice this is true for XQuery, false for XSLT
        Returns:
        true if the name can be supplied as a QName
      • getNewBaseURI

        public java.lang.String getNewBaseURI​(XPathContext context,
                                              NodeInfo copiedNode)
        Description copied from class: ElementCreator
        Get the base URI for the element being constructed
        Specified by:
        getNewBaseURI in class ElementCreator
        Parameters:
        context - the XPath dynamic evaluation context
        copiedNode - the node being copied (for xsl:copy), otherwise null
        Returns:
        the base URI of the constructed element
      • outputNamespaceNodes

        protected void outputNamespaceNodes​(XPathContext context,
                                            Receiver out,
                                            NodeName nameCode,
                                            NodeInfo copiedNode)
                                     throws XPathException
        Callback to output namespace nodes for the new element.
        Specified by:
        outputNamespaceNodes in class ElementCreator
        Parameters:
        context - The execution context
        out - the Receiver where the namespace nodes are to be written
        nameCode - The name of the element node being output
        copiedNode - Where this is a copied node, the node being copied
        Throws:
        XPathException
      • getInstructionNameCode

        public int getInstructionNameCode()
        Get the name of this instruction for diagnostic and tracing purposes
        Overrides:
        getInstructionNameCode in class Instruction
        Returns:
        a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace
      • explain

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