Package net.sf.saxon.expr
Class ExpressionVisitor
- java.lang.Object
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- net.sf.saxon.expr.ExpressionVisitor
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public class ExpressionVisitor extends java.lang.Object
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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Constructor Summary
Constructors Constructor Description ExpressionVisitor()
Create an ExpressionVisitor
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description Configuration
getConfiguration()
Get the Saxon configurationContainer
getContainer()
Get the container of the expressions being visitedExpression
getCurrentExpression()
Get the current expression, the one being visitedExecutable
getExecutable()
Get the Executable containing the expressions being visitedExpression
getParentExpression()
Get the parent expression of the current expression in the expression treejava.util.Stack
getStack()
Get the stack containing all the expressions currently being visitedStaticContext
getStaticContext()
Get the static context for the expressions being visited.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 oncestatic ExpressionVisitor
make(StaticContext env)
Factory method: make an expression visitorExpression
optimize(Expression exp, ItemType contextItemType)
Optimize an expression, via the ExpressionVisitorvoid
resetStaticProperties()
Reset the static properties for the current expression and for all its containing expressions.void
setConfiguration(Configuration configuration)
Set the Saxon configurationvoid
setContainer(Container container)
Set the container of the expressions being visitedvoid
setExecutable(Executable executable)
Set the Executable containing the expressions being visitedvoid
setStack(java.util.Stack stack)
Set the stack used to hold the expressions being visitedvoid
setStaticContext(StaticContext staticContext)
Set the static context for the expressions being visited.Expression
simplify(Expression exp)
Simplify an expression, via the ExpressionVisitorExpression
typeCheck(Expression exp, ItemType contextItemType)
Type check an expression, via the ExpressionVisitor
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Method Detail
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getConfiguration
public Configuration getConfiguration()
Get the Saxon configuration- Returns:
- the Saxon configuration
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setConfiguration
public void setConfiguration(Configuration configuration)
Set the Saxon configuration- Parameters:
configuration
- the Saxon configuration
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getContainer
public Container getContainer()
Get the container of the expressions being visited- Returns:
- the container
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setContainer
public void setContainer(Container container)
Set the container of the expressions being visited- Parameters:
container
- the container
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getExecutable
public Executable getExecutable()
Get the Executable containing the expressions being visited- Returns:
- the Executable
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setExecutable
public void setExecutable(Executable executable)
Set the Executable containing the expressions being visited- Parameters:
executable
- the Executable
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getStack
public java.util.Stack getStack()
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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setStack
public void setStack(java.util.Stack stack)
Set the stack used to hold the expressions being visited- Parameters:
stack
- the expression stack
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getStaticContext
public StaticContext 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
public void setStaticContext(StaticContext staticContext)
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
public Expression getCurrentExpression()
Get the current expression, the one being visited- Returns:
- the current expression
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make
public static ExpressionVisitor make(StaticContext env)
Factory method: make an expression visitor- Parameters:
env
- the static context- Returns:
- the new expression visitor
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simplify
public Expression simplify(Expression exp) throws XPathException
Simplify an expression, via the ExpressionVisitor- Parameters:
exp
- the expression to be simplified- Returns:
- the simplified expression
- Throws:
XPathException
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typeCheck
public Expression typeCheck(Expression exp, ItemType contextItemType) throws XPathException
Type check an expression, via the ExpressionVisitor- Parameters:
exp
- the expression to be typecheckedcontextItemType
- the static type of the context item for this expression- 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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optimize
public Expression optimize(Expression exp, ItemType 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- Returns:
- the rewritten expression
- Throws:
XPathException
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getParentExpression
public Expression 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
public 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 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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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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