net.sf.saxon.instruct

Class ComputedElement

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.instruct.Instruction

net.sf.saxon.instruct.ParentNodeConstructor

net.sf.saxon.instruct.ElementCreator

net.sf.saxon.instruct.ComputedElement

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, Container, Expression, TailCallReturner, InstructionInfoProvider

public class ComputedElement
extends ElementCreator

An instruction representing an xsl:element element in an XSLT stylesheet, or a computed element constructor in XQuery. (In both cases, if the element name is expressed as a compile-time expression, then a FixedElement instruction is used instead.)

See Also:

FixedElement, Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.instruct.ElementCreator

inheritNamespaces, validating

Fields inherited from class net.sf.saxon.instruct.ParentNodeConstructor

content, validation

Fields inherited from class net.sf.saxon.expr.ComputedExpression

locationId, staticProperties

Fields inherited from interface net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Constructors

Constructor and Description
ComputedElement(Expression elementName, Expression namespace, NamespaceResolver nsContext, SchemaType schemaType, int validation, boolean inheritNamespaces, boolean allowQName) Create an instruction that creates a new element node

Method Summary

Modifier and Type	Method and Description
void	checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
void	display(int level, java.io.PrintStream out, Configuration config) Display this instruction as an expression, for diagnostics
int	getInstructionNameCode() Get the name of this instruction for diagnostic and tracing purposes
ItemType	getItemType(TypeHierarchy th) Get the item type of the value returned by this instruction
int	getNameCode(XPathContext context) Callback from the superclass ElementCreator to get the nameCode for the element name
java.lang.String	getNewBaseURI(XPathContext context) Get the base URI for the element being constructed
java.util.Iterator	iterateSubExpressions() Get the immediate sub-expressions of this expression.
protected void	outputNamespaceNodes(XPathContext context, Receiver out) Callback to output namespace nodes for the new element.
protected void	promoteInst(PromotionOffer offer) Offer promotion for subexpressions.
boolean	replaceSubExpression(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
Expression	simplify(StaticContext env) Simplify an expression.
Expression	typeCheck(StaticContext env, ItemType contextItemType) Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.instruct.ElementCreator

checkContentForAttributes, computeSpecialProperties, evaluateItem, getActiveNamespaces, getImplementationMethod, getValidationMode, isInheritNamespaces, isValidating, processLeavingTail, setValidationMode, suppressValidation

Methods inherited from class net.sf.saxon.instruct.ParentNodeConstructor

createsNewNodes, getBaseURI, getCardinality, getContentExpression, getSchemaType, getValidationAction, isLazyConstruction, isNamespaceSensitive, optimize, setBaseURI, setContentExpression, setLazyConstruction, setSchemaType, verifyLazyConstruction

Methods inherited from class net.sf.saxon.instruct.Instruction

appendItem, assembleParams, assembleTunnelParams, computeCardinality, dynamicError, evaluateAsString, getInstructionInfo, getSourceLocator, isXSLT, iterate, process, promote

Methods inherited from class net.sf.saxon.expr.ComputedExpression

adoptChildExpression, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, typeError

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

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

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Description copied from class: ParentNodeConstructor

Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.

Specified by:

simplify in interface Expression

Overrides:

simplify in class ParentNodeConstructor

Parameters:

env - the static context

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Get the item type of the value returned by this instruction

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class ElementCreator

Parameters:

th -

Returns:

the item type

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()

Description copied from class: ParentNodeConstructor

Get the immediate sub-expressions of this expression.

Specified by:

iterateSubExpressions in interface Expression

Overrides:

iterateSubExpressions in class ParentNodeConstructor

Returns:

an iterator containing the sub-expressions of this expression

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)

Replace one subexpression by a replacement subexpression

Specified by:

replaceSubExpression in interface Container

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.

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

getNameCode

public int getNameCode(XPathContext context)
                throws XPathException,
                       XPathException

Callback from the superclass ElementCreator to get the nameCode for the element name

Specified by:

getNameCode in class ElementCreator

Parameters:

context - The evaluation context (not used)

Returns:

the name code for the element name

Throws:

XPathException

getNewBaseURI

public java.lang.String getNewBaseURI(XPathContext context)

Description copied from class: ElementCreator

Get the base URI for the element being constructed

Specified by:

getNewBaseURI in class ElementCreator

outputNamespaceNodes

protected void outputNamespaceNodes(XPathContext context,
                                    Receiver out)
                             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

Throws:

XPathException

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