Class ExpressionVisitor

java.lang.Object
net.sf.saxon.expr.parser.ExpressionVisitor
All Implemented Interfaces:
TypeCheckerEnvironment

public class ExpressionVisitor extends Object implements 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.
  • Constructor Details

    • ExpressionVisitor

      public ExpressionVisitor()
      Create an ExpressionVisitor
  • Method Details

    • getConfiguration

      public Configuration getConfiguration()
      Get the Saxon configuration
      Specified by:
      getConfiguration in interface TypeCheckerEnvironment
      Returns:
      the Saxon configuration
    • setConfiguration

      public void setConfiguration(Configuration configuration)
      Set the Saxon configuration
      Parameters:
      configuration - the Saxon configuration
    • getExecutable

      public Executable getExecutable()
      Get the Executable containing the expressions being visited
      Returns:
      the Executable
    • setExecutable

      public void setExecutable(Executable executable)
      Set the Executable containing the expressions being visited
      Parameters:
      executable - the Executable
    • getCollationMap

      public CollationMap getCollationMap()
      Specified by:
      getCollationMap in interface TypeCheckerEnvironment
    • getExpressionStack

      public Stack<Expression> 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
    • setExpressionStack

      public void setExpressionStack(Stack<Expression> expressionStack)
      Set the stack used to hold the expressions being visited
      Parameters:
      expressionStack - the expression stack
    • 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
    • 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
    • getCurrentExpression

      public Expression getCurrentExpression()
      Get the current expression, the one being visited
      Returns:
      the current expression
    • make

      public static ExpressionVisitor make(StaticContext env, Executable exec)
      Factory method: make an expression visitor
      Parameters:
      env - the static context
      exec - the executable
      Returns:
      the new expression visitor
    • issueWarning

      public void issueWarning(String message, SourceLocator locator)
      Issue a warning message
      Specified by:
      issueWarning in interface TypeCheckerEnvironment
      Parameters:
      message - the message
    • makeDynamicContext

      public XPathContext makeDynamicContext()
      Create a dynamic context suitable for early evaluation of constant subexpressions
      Specified by:
      makeDynamicContext in interface TypeCheckerEnvironment
    • simplify

      public Expression simplify(Expression exp) throws XPathException
      Simplify an expression, via the ExpressionVisitor
      Specified by:
      simplify in interface TypeCheckerEnvironment
      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
    • typeCheck

      public Expression typeCheck(Expression exp, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Type check an expression, via the ExpressionVisitor
      Specified by:
      typeCheck in interface TypeCheckerEnvironment
      Parameters:
      exp - the expression to be typechecked
      contextItemType - 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
    • 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
    • isOptimizeForStreaming

      public boolean isOptimizeForStreaming()
      Ask whether the visitor is to optimize expressions for evaluation in a streaming environment
      Returns:
      true if optimizing for streaming
    • optimize

      public Expression optimize(Expression exp, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Optimize an expression, via the ExpressionVisitor
      Parameters:
      exp - the expression to be typechecked
      contextItemType - 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
    • 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)
    • 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
    • isLoopingReference

      public boolean isLoopingReference(Binding binding, VariableReference ref)
    • 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.