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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.instruct.Instruction net.sf.saxon.expr.instruct.Choose
public class Choose
Compiled representation of an xsl:choose or xsl:if element in the stylesheet. Also used for typeswitch in XQuery.
Field Summary |
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Fields inherited from class net.sf.saxon.expr.Expression |
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EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD |
Constructor Summary | |
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Choose(Expression[] conditions,
Expression[] actions)
Construct an xsl:choose instruction |
Method Summary | |
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PathMap.PathMapNodeSet |
addToPathMap(PathMap pathMap,
PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. |
void |
checkForUpdatingSubexpressions()
Check to ensure that this expression does not contain any updating subexpressions. |
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. |
int |
computeCardinality()
Compute the cardinality of the sequence returned by evaluating this instruction |
int |
computeSpecialProperties()
Get the static properties of this expression (other than its type). |
Expression |
copy()
Copy an expression. |
boolean |
createsNewNodes()
Determine whether this instruction creates new nodes. |
Item |
evaluateItem(XPathContext context)
Evaluate an expression as a single item. |
void |
evaluatePendingUpdates(XPathContext context,
PendingUpdateList pul)
Evaluate an updating expression, adding the results to a Pending Update List. |
void |
explain(ExpressionPresenter out)
Diagnostic print of expression structure. |
Expression[] |
getActions()
Get the array of actions to be performed |
Expression[] |
getConditions()
Get the array of conditions to be tested |
int |
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). |
int |
getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes We assume that if there was only one condition then it was an xsl:if; this is not necessarily so, but it's adequate for tracing purposes. |
ItemType |
getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction |
boolean |
implementsStaticTypeCheck()
Determine whether this expression implements its own method for static type checking |
static boolean |
isSingleBranchChoice(Expression exp)
Test whether an expression is a single-branch choose, that is, an expression of the form if (condition) then exp else () |
boolean |
isUpdatingExpression()
Determine whether this is an updating expression as defined in the XQuery update specification |
boolean |
isVacuousExpression()
Determine whether this is a vacuous expression as defined in the XQuery update specification |
SequenceIterator<? extends Item> |
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence. |
EventIterator |
iterateEvents(XPathContext context)
Deliver the result of the expression as a sequence of events. |
Iterator<Expression> |
iterateSubExpressions()
Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction) |
static Expression |
makeConditional(Expression condition,
Expression thenExp)
Make a simple conditional expression (if (condition) then (thenExp) else () |
static Expression |
makeConditional(Expression condition,
Expression thenExp,
Expression elseExp)
Make a simple conditional expression (if (condition) then (thenExp) else (elseExp) |
int |
markTailFunctionCalls(StructuredQName qName,
int arity)
Mark tail-recursive calls on functions. |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
TailCall |
processLeavingTail(XPathContext context)
Process this instruction, that is, choose an xsl:when or xsl:otherwise child and process it. |
protected void |
promoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites. |
boolean |
replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression |
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression. |
Expression |
staticTypeCheck(SequenceType req,
boolean backwardsCompatible,
RoleLocator role,
TypeCheckerEnvironment visitor)
Static type checking for conditional expressions is delegated to the expression itself, and is performed separately on each branch of the conditional, so that dynamic checks are added only on those branches where the check is actually required. |
String |
toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform type checking of an expression and its subexpressions. |
Methods inherited from class net.sf.saxon.expr.instruct.Instruction |
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assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getExpressionName, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, process, promote |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Methods inherited from interface javax.xml.transform.SourceLocator |
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getColumnNumber, getLineNumber, getPublicId, getSystemId |
Constructor Detail |
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public Choose(Expression[] conditions, Expression[] actions)
conditions
- the conditions to be tested, in orderactions
- the actions to be taken when the corresponding condition is trueMethod Detail |
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public static Expression makeConditional(Expression condition, Expression thenExp, Expression elseExp)
condition
- the condition to be testedthenExp
- the expression to be evaluated if the condition is trueelseExp
- the expression to be evaluated if the condition is false
public static Expression makeConditional(Expression condition, Expression thenExp)
condition
- the condition to be testedthenExp
- the expression to be evaluated if the condition is true
public static boolean isSingleBranchChoice(Expression exp)
exp
- the expression to be tested
public Expression[] getConditions()
public Expression[] getActions()
public int getInstructionNameCode()
getInstructionNameCode
in class Instruction
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Instruction
visitor
- expression visitor object
XPathException
- if an error is discovered during expression
rewritingpublic Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Expression
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.
typeCheck
in class Expression
visitor
- an expression visitorcontextItemType
- 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
XPathException
- if an error is discovered during this phase
(typically a type error)public boolean implementsStaticTypeCheck()
implementsStaticTypeCheck
in class Expression
public Expression staticTypeCheck(SequenceType req, boolean backwardsCompatible, RoleLocator role, TypeCheckerEnvironment visitor) throws XPathException
staticTypeCheck
in class Expression
req
- the required typebackwardsCompatible
- true if backwards compatibility mode appliesrole
- the role of the expression in relation to the required typevisitor
- an expression visitor
XPathException
- if failures occur, for example if the static type of one branch of the conditional
is incompatible with the required typepublic Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Expression
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.
optimize
in class Expression
visitor
- an expression visitorcontextItemType
- 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
XPathException
- if an error is discovered during this phase
(typically a type error)public Expression copy()
copy
in class Expression
public void checkForUpdatingSubexpressions() throws XPathException
checkForUpdatingSubexpressions
in class Expression
XPathException
- if the expression has a non-permitted updateing subexpressionpublic boolean isUpdatingExpression()
isUpdatingExpression
in class Expression
public boolean isVacuousExpression()
isVacuousExpression
in class Expression
public int getImplementationMethod()
getImplementationMethod
in class Instruction
Expression.ITERATE_METHOD
or Expression.EVALUATE_METHOD
or
Expression.PROCESS_METHOD
public int markTailFunctionCalls(StructuredQName qName, int arity)
markTailFunctionCalls
in class Expression
qName
- the name of the functionarity
- the arity (number of parameters) of the function
public ItemType getItemType(TypeHierarchy th)
getItemType
in class Instruction
th
- Type hierarchy cache
public int computeCardinality()
computeCardinality
in class Instruction
public int computeSpecialProperties()
computeSpecialProperties
in class Instruction
public final boolean createsNewNodes()
createsNewNodes
in class Instruction
public Iterator<Expression> iterateSubExpressions()
iterateSubExpressions
in class Expression
public boolean replaceSubExpression(Expression original, Expression replacement)
replaceSubExpression
in class Expression
original
- the original subexpressionreplacement
- the replacement subexpression
protected void promoteInst(PromotionOffer offer) throws XPathException
promoteInst
in class Instruction
offer
- The type of rewrite being offered
XPathException
public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException
checkPermittedContents
in class Expression
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 typeenv
- the static contextwhole
- 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
XPathException
- if the value delivered by this expression cannot be part of the content model
of the given typepublic PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.
addToPathMap
in class Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
- the set of PathMap nodes to which the paths from this expression should be appended
public String toString()
toString
in class Expression
public void explain(ExpressionPresenter out)
explain
in class Expression
out
- the expression presenter used to display the structurepublic TailCall processLeavingTail(XPathContext context) throws XPathException
processLeavingTail
in interface TailCallReturner
processLeavingTail
in class Instruction
context
- the dynamic context of this transformation
XPathException
- if any non-recoverable dynamic error occurspublic Item evaluateItem(XPathContext context) throws XPathException
evaluateItem
in class Instruction
context
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expressionpublic SequenceIterator<? extends Item> iterate(XPathContext context) throws XPathException
iterate
in class Instruction
context
- supplies the context for evaluation
XPathException
- if any dynamic error occurs evaluating the
expressionpublic EventIterator iterateEvents(XPathContext context) throws XPathException
The events (of class PullEvent
) are either complete
items, or one of startElement, endElement, startDocument, or endDocument, known
as semi-nodes. The stream of events may also include a nested EventIterator.
If a start-end pair exists in the sequence, then the events between
this pair represent the content of the document or element. The content sequence will
have been processed to the extent that any attribute and namespace nodes in the
content sequence will have been merged into the startElement event. Namespace fixup
will have been performed: that is, unique prefixes will have been allocated to element
and attribute nodes, and all namespaces will be declared by means of a namespace node
in the startElement event or in an outer startElement forming part of the sequence.
However, duplicate namespaces may appear in the sequence.
The content of an element or document may include adjacent or zero-length text nodes, atomic values, and nodes represented as nodes rather than broken down into events.
iterateEvents
in class Expression
context
- The dynamic evaluation context
XPathException
- if a dynamic error occurs during expression evaluationpublic void evaluatePendingUpdates(XPathContext context, PendingUpdateList pul) throws XPathException
evaluatePendingUpdates
in class Expression
context
- the XPath dynamic evaluation contextpul
- the pending update list to which the results should be written
XPathException
- if evaluation fails
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