net.sf.saxon.instruct
Class ValueOf

java.lang.Object
  |
  +--net.sf.saxon.instruct.Instruction
        |
        +--net.sf.saxon.instruct.ExprInstruction
              |
              +--net.sf.saxon.instruct.SimpleNodeConstructor
                    |
                    +--net.sf.saxon.instruct.ValueOf

All Implemented Interfaces:

Expression, Instr, Locatable, java.io.Serializable, javax.xml.transform.SourceLocator

public final class ValueOf

extends SimpleNodeConstructor

An xsl:value-of element in the stylesheet.
The xsl:value-of element takes attributes:

• a mandatory attribute select="expression". This must be a valid String expression
• an optional disable-output-escaping attribute, value "yes" or "no"
• an optional separator attribute. This is handled at compile-time: if the separator attribute is present, the select expression passed in here will be a call to the string-join() function.

See Also:

Serialized Form

Field Summary

 

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

select, separator

 

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

children

 

Constructor Summary

ValueOf(Expression select, boolean disable)

 

Method Summary
void	display(int level, NamePool pool)           Display this instruction as an expression, for diagnostics
Item	evaluateItem(XPathContext context)           Evaluate as an expression.
int	getCardinality()           Determine the static cardinality of the expression.
java.lang.String	getInstructionName()           Get the name of this instruction for diagnostic and tracing purposes
ItemType	getItemType()           Determine the data type of the expression, if possible.
TailCall	processLeavingTail(XPathContext context)           ProcessLeavingTail: called to do the real work of this instruction.
void	promoteInst(PromotionOffer offer)           Offer promotion for subexpressions.
void	typeCheck(StaticContext env)

 

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

analyze, evaluateNameCode, expandChildren, getXPathExpressions, setSelect, setSeparator

 

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

effectiveBooleanValue, evaluateAsString, getDependencies, getSpecialProperties, getSubExpressions, iterate, promote, simplify

 

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

assembleParams, assembleTunnelParams, displayChildren, dynamicError, dynamicError, getChildren, getColumnNumber, getExecutable, getInstructionNamespace, getLineNumber, getPublicId, getSourceLocator, getSystemId, process, processChildren, processChildrenLeavingTail, recoverableError, setChildren, setExecutable, setSourceLocation

 

Methods inherited from class java.lang.Object

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

 

Constructor Detail

ValueOf

public ValueOf(Expression select,
               boolean disable)

getInstructionName

public java.lang.String getInstructionName()

Get the name of this instruction for diagnostic and tracing purposes

Specified by:

getInstructionName in class Instruction

promoteInst

public 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 SimpleNodeConstructor

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

getItemType

public ItemType getItemType()

Description copied from interface: Expression

Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class Instruction

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

getCardinality

public int getCardinality()

Description copied from interface: Expression

Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.

This method should always return a result, though it may be the best approximation that is available at the time.

Specified by:

getCardinality in interface Expression

Overrides:

getCardinality in class Instruction

Returns:

one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

typeCheck

public void typeCheck(StaticContext env)
               throws XPathException

Specified by:

typeCheck in class SimpleNodeConstructor

XPathException

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws javax.xml.transform.TransformerException

Description copied from class: Instruction

ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.

Specified by:

processLeavingTail in interface Instr

Specified by:

processLeavingTail in class Instruction

Parameters:

context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.

Returns:

null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.

javax.xml.transform.TransformerException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Description copied from class: SimpleNodeConstructor

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 SimpleNodeConstructor

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

display

public void display(int level,
                    NamePool pool)

Display this instruction as an expression, for diagnostics

Specified by:

display in interface Expression

Overrides:

display in class SimpleNodeConstructor

Parameters:

level - indentation level for this expression