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.
        schemaType - The required schema type for the content
        allowQName -
    • Method Detail

      • typeCheck

        public Expression typeCheck​(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException
        Description copied from interface: 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 parent pointer and 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.

        Specified by:
        typeCheck in interface Expression
        Overrides:
        typeCheck in class ParentNodeConstructor
        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
      • 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.
        Specified by:
        checkPermittedContents in interface Expression
        Overrides:
        checkPermittedContents in class ComputedExpression
        Parameters:
        parentType - The schema type
        env - the static context
        whole - true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part
        Throws:
        XPathException - if the expression doesn't match the required content type
      • getInstructionNameCode

        public int getInstructionNameCode()
        Get the name of this instruction for diagnostic and tracing purposes
        Overrides:
        getInstructionNameCode in class Instruction
      • display

        public void display​(int level,
                            java.io.PrintStream out,
                            Configuration config)
        Display this instruction as an expression, for diagnostics
        Parameters:
        level - indentation level for this expression
        out - Output destination