

PREV CLASS NEXT CLASS  FRAMES NO FRAMES  
SUMMARY: NESTED  FIELD  CONSTR  METHOD  DETAIL: FIELD  CONSTR  METHOD 
java.lang.Object net.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 runtime 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:foreachgroup 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 

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, 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 subexpressions of this expression. 
Expression 
optimize(ExpressionVisitor visitor,
ItemType 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,
ItemType 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 wrappedMethod Detail 

public Pattern getPattern()
public int getImplementationMethod()
getImplementationMethod
in class Expression
Expression.ITERATE_METHOD
or Expression.EVALUATE_METHOD
or
Expression.PROCESS_METHOD
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Expression
visitor
 an expression visitor
XPathException
 if an error is discovered during expression
rewritingpublic Expression optimize(ExpressionVisitor visitor, ItemType 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 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 typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
This checks statically that the operands of the expression have the correct type; if necessary it generates code to do runtime type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a runtime 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 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)protected int computeCardinality()
Expression
computeCardinality
in class Expression
StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.EXACTLY_ONE
, StaticProperty.ALLOWS_ONE_OR_MORE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
public Expression copy()
copy
in class Expression
public boolean hasLoopingSubexpression(Expression child)
hasLoopingSubexpression
in class Expression
child
 the child expression
public Expression promote(PromotionOffer offer, Expression parent) throws XPathException
promote
in class Expression
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 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 Expression
StaticProperty.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 Expression
th
 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 Expression
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
public Container getContainer()
getContainer
in class Expression
public Item evaluateItem(XPathContext context) throws XPathException
evaluateItem
in interface EvaluableItem
evaluateItem
in class Expression
context
 The context in which the expression is to be evaluated
XPathException
 if any dynamic error occurs evaluating the
expressionpublic SequenceIterator iterate(XPathContext context) throws XPathException
iterate
in interface SequenceIterable
iterate
in class Expression
context
 supplies the context for evaluation
XPathException
 if any dynamic error occurs evaluating the
expressionpublic boolean effectiveBooleanValue(XPathContext context) throws XPathException
effectiveBooleanValue
in class Expression
context
 The context in which the expression is to be evaluated
XPathException
 if any dynamic error occurs evaluating the
expressionpublic CharSequence evaluateAsString(XPathContext context) throws XPathException
evaluateAsString
in class Expression
context
 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 Expression
context
 The dynamic context, giving access to the current node,
the current variables, etc.
XPathException
public void explain(ExpressionPresenter out)
explain
in class Expression
out
 the expression presenter used to display the structurepublic void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException
checkPermittedContents
in class Expression
parentType
 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


PREV CLASS NEXT CLASS  FRAMES NO FRAMES  
SUMMARY: NESTED  FIELD  CONSTR  METHOD  DETAIL: FIELD  CONSTR  METHOD 