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java.lang.Object net.sf.saxon.expr.Expression com.saxonica.expr.EvaluateInstr
public final class EvaluateInstr
An EvaluateInstr is the compiled form of an xsl:evaluate instruction
The implementation maintains a cache of compiled expressions, provided that the namespace context is not constructed dynamically. The cache is an LRU cache with a fixed size of 100 entries. This is to avoid uncontrolled use of memory when the XPath expressions are completely dynamic and each one is unique.
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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EvaluateInstr(Expression xpath,
SequenceType requiredType,
Expression baseUriExpr,
Expression namespaceContextExpr,
Expression schemaAwareExpr)
Create an xsl:evaluate instruction |
Method Summary | |
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PathMap.PathMapNodeSet |
addToPathMap(PathMap pathMap,
PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. |
protected int |
computeCardinality()
Compute the static cardinality of this expression |
int |
computeDependencies()
Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. |
Expression |
copy()
Copy an expression. |
void |
explain(ExpressionPresenter out)
Diagnostic print of expression structure. |
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 items returned by this expression |
SequenceIterator<? extends Item> |
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence. |
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) |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
Expression |
promote(PromotionOffer offer,
Expression parent)
Offer promotion for this subexpression. |
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 |
void |
setActualParameters(WithParam[] params)
|
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public EvaluateInstr(Expression xpath, SequenceType requiredType, Expression baseUriExpr, Expression namespaceContextExpr, Expression schemaAwareExpr)
xpath
- The expression that returns the string that is to be parsed as an XPath expressionrequiredType
- the required type of the result of evaluating the XPath expressionbaseUriExpr
- the expression whose value is used as the static base URI of the XPath expressionnamespaceContextExpr
- the expression that delivers a node whose namespace context provides the
static namespace context for the XPath expressionschemaAwareExpr
- an expression whose value is true if the XPath expression is to be treated as schema
aware, or false otherwiseMethod Detail |
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public void setActualParameters(WithParam[] params)
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Expression
visitor
- the expression visitor
XPathException
- if an error is discovered during expression
rewritingpublic Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
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 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 final ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
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 promote(PromotionOffer offer, Expression parent) throws XPathException
Expression
This method must be overridden for any Expression that has subexpressions.
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
- the containing expression in the expression tree
XPathException
- if any error is detectedpublic 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 nodes in the path map that are affected
public int computeDependencies()
computeDependencies
in class Expression
protected void promoteInst(PromotionOffer offer) throws XPathException
offer
- The type of rewrite being offered
XPathException
- if an error is detectedpublic 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 int getImplementationMethod()
getImplementationMethod
in class Expression
Expression.ITERATE_METHOD
or Expression.EVALUATE_METHOD
or
Expression.PROCESS_METHOD
public Expression copy()
copy
in class Expression
public SequenceIterator<? extends Item> iterate(XPathContext context) throws XPathException
Expression
iterate
in class Expression
context
- supplies the context for evaluation
XPathException
- if any dynamic error occurs evaluating the
expressionpublic void explain(ExpressionPresenter out)
explain
in class Expression
out
- the expression presenter used to display the structure
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