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java.lang.Objectnet.sf.saxon.expr.Expression
net.sf.saxon.pattern.PatternSponsor
public class PatternSponsor
The PatternSponsor class allows a Pattern to be treated like an expression. Although patterns are not evaluated at run-time in the same way as expressions, they need to be manipulated in much the same way as expressions at compile time: for example variables need to be bound, dependencies need to be analyzed, and so on. This is especially true of patterns appearing in the xsl:number and xsl:for-each-group instructions (less so for the more common match patterns in xsl:template).
This class implements the Expression interface, so that an Expression can have a PatternSponsor as a subexpression; it wraps a Pattern.
A Pattern is treated as a boolean expression that returns true if the pattern matches
the context node. It is evaluated in that way only when obtained through the s9api
XPathCompiler.compilePattern(String) method.
| Field Summary |
|---|
| Fields inherited from class net.sf.saxon.expr.Expression |
|---|
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 | |
|---|---|
PatternSponsor(Pattern pattern)
Create a sponsor expression for a pattern |
|
| Method Summary | |
|---|---|
void |
checkPermittedContents(SchemaType parentType,
StaticContext env,
boolean whole)
Check statically that the results of the expression are capable of constructing the content of a given schema type. |
protected int |
computeCardinality()
Compute the static cardinality of this expression |
Expression |
copy()
Copy an expression. |
boolean |
effectiveBooleanValue(XPathContext context)
Get the effective boolean value of the expression. |
CharSequence |
evaluateAsString(XPathContext context)
Evaluate an expression as a String. |
Item |
evaluateItem(XPathContext context)
Evaluate an expression as a single item. |
void |
explain(ExpressionPresenter out)
Diagnostic print of expression structure. |
int |
getCardinality()
Determine the static cardinality of the expression. |
Container |
getContainer()
Get the container that immediately contains this expression. |
int |
getDependencies()
Determine which aspects of the context the expression depends on. |
int |
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible. |
Pattern |
getPattern()
Get the wrapped pattern |
boolean |
hasLoopingSubexpression(Expression child)
Treat all subexpressions of a pattern as "looping" subexpresions, that is, assume they are evaluated repeatedly |
SequenceIterator |
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence. |
Iterator<Expression> |
iterateSubExpressions()
Get the immediate sub-expressions of this expression. |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
void |
process(XPathContext context)
Process the instruction, without returning any tail calls |
Expression |
promote(PromotionOffer offer,
Expression parent)
Offer promotion for this subexpression. |
boolean |
replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression |
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform type checking of an expression and its subexpressions. |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Constructor Detail |
|---|
public PatternSponsor(Pattern pattern)
pattern - the pattern being wrapped| Method Detail |
|---|
public Pattern getPattern()
public int getImplementationMethod()
getImplementationMethod in class ExpressionExpression.ITERATE_METHOD or Expression.EVALUATE_METHOD or
Expression.PROCESS_METHOD
public Expression simplify(ExpressionVisitor visitor)
throws XPathException
simplify in class Expressionvisitor - an expression visitor
XPathException - if an error is discovered during expression
rewriting
public Expression optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
throws XPathException
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 Expressionvisitor - 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 typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
throws XPathException
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.
typeCheck in class Expressionvisitor - 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)protected int computeCardinality()
Expression
computeCardinality in class ExpressionStaticProperty.ALLOWS_ZERO_OR_ONE,
StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE,
StaticProperty.ALLOWS_ZERO_OR_MOREpublic Expression copy()
copy in class Expressionpublic boolean hasLoopingSubexpression(Expression child)
hasLoopingSubexpression in class Expressionchild - the child expression
public Expression promote(PromotionOffer offer,
Expression parent)
throws XPathException
promote in class Expressionoffer - 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 expressionparent -
XPathException - if any error is detectedpublic int getCardinality()
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.
getCardinality in class ExpressionStaticProperty.ALLOWS_ONE,
StaticProperty.ALLOWS_ZERO_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_ONE,
StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.EMPTY.public ItemType getItemType(TypeHierarchy th)
This method should always return a result, though it may be the best approximation that is available at the time.
getItemType in class Expressionth - the type hierarchy cache
public int getDependencies()
StaticProperty.DEPENDS_ON_CONTEXT_ITEM and
StaticProperty.DEPENDS_ON_CURRENT_ITEM. The default implementation combines the intrinsic
dependencies of this expression with the dependencies of the subexpressions,
computed recursively. This is overridden for expressions such as FilterExpression
where a subexpression's dependencies are not necessarily inherited by the parent
expression.
getDependencies in class Expressionpublic Iterator<Expression> iterateSubExpressions()
iterateSubExpressions in class Expression
public boolean replaceSubExpression(Expression original,
Expression replacement)
replaceSubExpression in class Expressionoriginal - the original subexpressionreplacement - the replacement subexpression
public Container getContainer()
getContainer in class Expression
public Item evaluateItem(XPathContext context)
throws XPathException
evaluateItem in class Expressioncontext - The context in which the expression is to be evaluated
XPathException - if any dynamic error occurs evaluating the
expression
public SequenceIterator iterate(XPathContext context)
throws XPathException
iterate in class Expressioncontext - supplies the context for evaluation
XPathException - if any dynamic error occurs evaluating the
expression
public boolean effectiveBooleanValue(XPathContext context)
throws XPathException
effectiveBooleanValue in class Expressioncontext - The context in which the expression is to be evaluated
XPathException - if any dynamic error occurs evaluating the
expression
public CharSequence evaluateAsString(XPathContext context)
throws XPathException
evaluateAsString in class Expressioncontext - The context in which the expression is to be evaluated
XPathException - if any dynamic error occurs evaluating the
expression
ClassCastException - if the result type of the
expression is not xs:string?
public void process(XPathContext context)
throws XPathException
process in class Expressioncontext - The dynamic context, giving access to the current node,
the current variables, etc.
XPathException - if a dynamic error occurspublic void explain(ExpressionPresenter out)
explain in class Expressionout - the expression presenter used to display the structure
public void checkPermittedContents(SchemaType parentType,
StaticContext env,
boolean whole)
throws XPathException
checkPermittedContents in class ExpressionparentType - The schema typeenv - the static contextwhole - 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
XPathException - if the expression doesn't match the required content type
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