Package net.sf.saxon.expr.parser
Class ExpressionVisitor
java.lang.Object
net.sf.saxon.expr.parser.ExpressionVisitor
- All Implemented Interfaces:
TypeCheckerEnvironment
The ExpressionVisitor supports the various phases of processing of an expression tree which require
a recursive walk of the tree structure visiting each node in turn. In maintains a stack holding the
ancestor nodes of the node currently being visited.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic class
A data structure that represents the required type of the context item, together with information about whether it is known to be present or absent or whether it is not known statically whether it is present or absent. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionGet the Saxon configurationGet the current expression, the one being visitedGet the Executable containing the expressions being visitedGet the stack containing all the expressions currently being visitedGet the parent expression of the current expression in the expression treeGet the static context for the expressions being visited.boolean
isLoopingReference
(Binding binding, VariableReference ref) boolean
isLoopingSubexpression
(Expression ancestor) Return true if the current expression at the top of the visitor's stack is evaluated repeatedly when a given ancestor expression is evaluated onceboolean
Ask whether the visitor is to optimize expressions for evaluation in a streaming environmentvoid
issueWarning
(String message, SourceLocator locator) Issue a warning messagestatic ExpressionVisitor
make
(StaticContext env, Executable exec) Factory method: make an expression visitorCreate a dynamic context suitable for early evaluation of constant subexpressionsoptimize
(Expression exp, ExpressionVisitor.ContextItemType contextItemType) Optimize an expression, via the ExpressionVisitorfinal void
Reset the static properties for the current expression and for all its containing expressions.void
setConfiguration
(Configuration configuration) Set the Saxon configurationvoid
setExecutable
(Executable executable) Set the Executable containing the expressions being visitedvoid
setExpressionStack
(Stack<Expression> expressionStack) Set the stack used to hold the expressions being visitedvoid
setOptimizeForStreaming
(boolean option) Tell the visitor to optimize expressions for evaluation in a streaming environmentvoid
setStaticContext
(StaticContext staticContext) Set the static context for the expressions being visited.simplify
(Expression exp) Simplify an expression, via the ExpressionVisitortypeCheck
(Expression exp, ExpressionVisitor.ContextItemType contextItemType) Type check an expression, via the ExpressionVisitor
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Constructor Details
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ExpressionVisitor
public ExpressionVisitor()Create an ExpressionVisitor
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Method Details
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getConfiguration
Get the Saxon configuration- Specified by:
getConfiguration
in interfaceTypeCheckerEnvironment
- Returns:
- the Saxon configuration
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setConfiguration
Set the Saxon configuration- Parameters:
configuration
- the Saxon configuration
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getExecutable
Get the Executable containing the expressions being visited- Returns:
- the Executable
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setExecutable
Set the Executable containing the expressions being visited- Parameters:
executable
- the Executable
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getCollationMap
- Specified by:
getCollationMap
in interfaceTypeCheckerEnvironment
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getExpressionStack
Get the stack containing all the expressions currently being visited- Returns:
- the expression stack holding all the containing expressions of the current expression;
the objects on this Stack are instances of
Expression
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setExpressionStack
Set the stack used to hold the expressions being visited- Parameters:
expressionStack
- the expression stack
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getStaticContext
Get the static context for the expressions being visited. Note: this may not reflect all changes in static context (e.g. namespace context, base URI) applying to nested expressions- Returns:
- the static context
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setStaticContext
Set the static context for the expressions being visited. Note: this may not reflect all changes in static context (e.g. namespace context, base URI) applying to nested expressions- Parameters:
staticContext
- the static context
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getCurrentExpression
Get the current expression, the one being visited- Returns:
- the current expression
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make
Factory method: make an expression visitor- Parameters:
env
- the static contextexec
- the executable- Returns:
- the new expression visitor
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issueWarning
Issue a warning message- Specified by:
issueWarning
in interfaceTypeCheckerEnvironment
- Parameters:
message
- the message
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makeDynamicContext
Create a dynamic context suitable for early evaluation of constant subexpressions- Specified by:
makeDynamicContext
in interfaceTypeCheckerEnvironment
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simplify
Simplify an expression, via the ExpressionVisitor- Specified by:
simplify
in interfaceTypeCheckerEnvironment
- Parameters:
exp
- the expression to be simplified. Possibly null.- Returns:
- the simplified expression. Returns null if and only if the supplied expression is null.
- Throws:
XPathException
- if any error occurs
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typeCheck
public Expression typeCheck(Expression exp, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Type check an expression, via the ExpressionVisitor- Specified by:
typeCheck
in interfaceTypeCheckerEnvironment
- Parameters:
exp
- the expression to be typecheckedcontextItemType
- the static type of the context item for this expression. The argument can be set to null to indicate that it is known that the context item will be absent.- Returns:
- the expression that results from type checking (this may be wrapped in expressions that perform dynamic checking of the item type or cardinality, or that perform atomization or numeric promotion)
- Throws:
XPathException
- if static type checking fails, that is, if the expression cannot possibly deliver a value of the required type
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setOptimizeForStreaming
public void setOptimizeForStreaming(boolean option) Tell the visitor to optimize expressions for evaluation in a streaming environment- Parameters:
option
- true if optimizing for streaming
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isOptimizeForStreaming
public boolean isOptimizeForStreaming()Ask whether the visitor is to optimize expressions for evaluation in a streaming environment- Returns:
- true if optimizing for streaming
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optimize
public Expression optimize(Expression exp, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Optimize an expression, via the ExpressionVisitor- Parameters:
exp
- the expression to be typecheckedcontextItemType
- the static type of the context item for this expression. Passing null indicates that the context item will always be absent- Returns:
- the rewritten expression
- Throws:
XPathException
- if a static error is found
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getParentExpression
Get the parent expression of the current expression in the expression tree- Returns:
- the parent of the current expression (or null if this is the root)
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isLoopingSubexpression
Return true if the current expression at the top of the visitor's stack is evaluated repeatedly when a given ancestor expression is evaluated once- Parameters:
ancestor
- the ancestor expression. May be null, in which case the search goes all the way to the base of the stack.- Returns:
- true if the current expression is evaluated repeatedly
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isLoopingReference
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resetStaticProperties
public final void resetStaticProperties()Reset the static properties for the current expression and for all its containing expressions. This should be done whenever the expression is changed in a way that might affect the properties. It causes the properties to be recomputed next time they are needed.
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