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java.lang.Objectnet.sf.saxon.pattern.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. However, it is not currently evaluated in that way.
| Field Summary |
| Fields inherited from interface net.sf.saxon.expr.Expression |
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD |
| Constructor Summary | |
PatternSponsor(Pattern pattern)
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| 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. |
void |
display(int level,
java.io.PrintStream out,
Configuration config)
Diagnostic print of expression structure. |
boolean |
effectiveBooleanValue(XPathContext context)
Get the effective boolean value of the expression. |
java.lang.String |
evaluateAsString(XPathContext context)
Evaluate an expression as a String. |
Item |
evaluateItem(XPathContext context)
Evaluate an expression as a single item. |
int |
getCardinality()
Determine the static cardinality of the 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. |
Container |
getParentExpression()
Get the container that immediately contains this expression. |
Pattern |
getPattern()
Get the wrapped pattern |
int |
getSpecialProperties()
Get the static properties of this expression (other than its type). |
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. |
Expression |
optimize(Optimizer opt,
StaticContext env,
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)
Offer promotion for this subexpression. |
Expression |
simplify(StaticContext env)
Simplify an expression. |
Expression |
typeCheck(StaticContext env,
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, toString, wait, wait, wait |
| Constructor Detail |
public PatternSponsor(Pattern pattern)
| Method Detail |
public Pattern getPattern()
public int getImplementationMethod()
getImplementationMethod in interface Expression
public Expression simplify(StaticContext env)
throws XPathException
simplify in interface Expressionenv - the static context
StaticError - if an error is discovered during expression
rewriting
XPathException
public Expression optimize(Optimizer opt,
StaticContext env,
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 interface Expressionopt - 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 expressioncontextItemType - 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
StaticError - if an error is discovered during this phase
(typically a type error)
XPathException
public Expression typeCheck(StaticContext env,
ItemType 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 interface Expressionenv - the static context of the expressioncontextItemType - 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
StaticError - if an error is discovered during this phase
(typically a type error)
XPathException
public Expression promote(PromotionOffer offer)
throws XPathException
promote in interface 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 expression
XPathException - if any error is detectedpublic int getSpecialProperties()
getSpecialProperties in interface Expressionpublic 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 interface 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 interface Expressionth -
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 interface Expressionpublic java.util.Iterator iterateSubExpressions()
iterateSubExpressions in interface Expressionpublic Container getParentExpression()
getParentExpression in interface Expression
public Item evaluateItem(XPathContext context)
throws XPathException
evaluateItem in interface 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 interface Expressioncontext - supplies the context for evaluation
XPathException - if any dynamic error occurs evaluating the
expression
public boolean effectiveBooleanValue(XPathContext context)
throws XPathException
effectiveBooleanValue in interface Expressioncontext - The context in which the expression is to be evaluated
XPathException - if any dynamic error occurs evaluating the
expression
public java.lang.String evaluateAsString(XPathContext context)
throws XPathException
evaluateAsString in interface Expressioncontext - The context in which the expression is to be evaluated
XPathException - if any dynamic error occurs evaluating the
expression
java.lang.ClassCastException - if the result type of the
expression is not xs:string?
public void process(XPathContext context)
throws XPathException
process in interface Expressioncontext - The dynamic context, giving access to the current node,
the current variables, etc.
XPathException
public void display(int level,
java.io.PrintStream out,
Configuration config)
display in interface Expressionlevel - indentation level for this expressionout - Output destinationconfig -
public void checkPermittedContents(SchemaType parentType,
StaticContext env,
boolean whole)
throws XPathException
checkPermittedContents in interface 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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