net.sf.saxon.instruct
Class SimpleNodeConstructor

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.instruct.Instruction
          net.sf.saxon.instruct.SimpleNodeConstructor

All Implemented Interfaces:

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

Direct Known Subclasses:

Attribute, Comment, FixedAttribute, Namespace, ProcessingInstruction, ValueOf

public abstract class SimpleNodeConstructor

extends Instruction

Common superclass for XSLT instructions whose content template produces a text value: xsl:attribute, xsl:comment, xsl:processing-instruction, xsl:namespace, and xsl:text

See Also:

Serialized Form

Field Summary

protected Expression

select

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

SimpleNodeConstructor()

Method Summary

protected java.lang.String	checkContent(java.lang.String data, XPathContext context) Check the content of the node, and adjust it if necessary.
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
boolean	createsNewNodes() Determine whether this instruction creates new nodes.
void	display(int level, NamePool pool, java.io.PrintStream out) Display this instruction as an expression, for diagnostics
Item	evaluateItem(XPathContext context) Evaluate as an expression.
protected int	evaluateNameCode(XPathContext context)
java.lang.CharSequence	expandChildren(XPathContext context) Expand the stylesheet elements subordinate to this one, returning the result as a string.
Expression	getSelect()
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
java.util.Iterator	iterateSubExpressions() Get the immediate sub-expressions of this expression.
abstract void	localTypeCheck(StaticContext env, ItemType contextItemType)
Expression	optimize(Optimizer opt, StaticContext env, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
protected void	promoteInst(PromotionOffer offer) Offer promotion for subexpressions.
void	setSelect(Expression select, Configuration config)
Expression	simplify(StaticContext env) Simplify an expression.
Expression	typeCheck(StaticContext env, ItemType contextItemType) The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions.

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

appendItem, assembleParams, assembleTunnelParams, computeCardinality, dynamicError, evaluateAsString, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, process, processLeavingTail, promote

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

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

Field Detail

select

protected Expression select

Constructor Detail

SimpleNodeConstructor

public SimpleNodeConstructor()

Method Detail

setSelect

public void setSelect(Expression select,
                      Configuration config)
               throws StaticError

Throws:

StaticError

getSelect

public Expression getSelect()

createsNewNodes

public final boolean createsNewNodes()

Determine whether this instruction creates new nodes. This implementation returns true.

Overrides:

createsNewNodes in class Instruction

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Description copied from class: Instruction

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

Specified by:

simplify in class Instruction

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:

computeSpecialProperties in class Instruction

Returns:

a set of flags indicating static properties of this expression

localTypeCheck

public abstract void localTypeCheck(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException

Throws:

XPathException

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions. In this case the required type for the select expression is a single string.

Parameters:

env - The static context for the query

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 rewritten expression

Throws:

XPathException - if any static errors are found in this expression or any of its children

optimize

public Expression optimize(Optimizer opt,
                           StaticContext env,
                           ItemType contextItemType)
                    throws XPathException

Description copied from interface: Expression

Perform optimisation of an expression and its subexpressions.

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.

Parameters:

opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.

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 if appropriate to optimize execution

Throws:

XPathException

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()

Description copied from class: ComputedExpression

Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Specified by:

iterateSubExpressions in interface Expression

Overrides:

iterateSubExpressions in class ComputedExpression

Returns:

an iterator containing the sub-expressions of this expression

expandChildren

public java.lang.CharSequence expandChildren(XPathContext context)
                                      throws XPathException

Expand the stylesheet elements subordinate to this one, returning the result as a string. The expansion must not generate any element or attribute nodes.

Parameters:

context - The dynamic context for the transformation

Throws:

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate as an expression. We rely on the fact that when these instructions are generated by XQuery, there will always be a valueExpression to evaluate the content

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class Instruction

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

checkContent

protected java.lang.String checkContent(java.lang.String data,
                                        XPathContext context)
                                 throws DynamicError

Check the content of the node, and adjust it if necessary. The checks depend on the node kind.

Parameters:

data - the supplied content

context - the dynamic context

Returns:

the original content, unless adjustments are needed

Throws:

DynamicError - if the content is invalid

evaluateNameCode

protected int evaluateNameCode(XPathContext context)
                        throws XPathException,
                               XPathException

Throws:

XPathException

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Description copied from class: Instruction

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

Specified by:

iterate in interface Expression

Overrides:

iterate in class Instruction

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

display

public void display(int level,
                    NamePool pool,
                    java.io.PrintStream out)

Display this instruction as an expression, for diagnostics

Parameters:

level - indentation level for this expression

pool - NamePool used to expand any names appearing in the expression

out - Output destination

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 Instruction

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