org.exist.xquery
Class ExtensionExpression

java.lang.Object
  extended by org.exist.xquery.AbstractExpression
      extended by org.exist.xquery.ExtensionExpression
All Implemented Interfaces:
Expression

public class ExtensionExpression
extends AbstractExpression

Implements an XQuery extension expression. An extension expression starts with a list of pragmas, followed by an expression enclosed in curly braces. For evaluation details check {eval(Sequence, Item).

Author:
wolf

Field Summary
 
Fields inherited from interface org.exist.xquery.Expression
DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_NODE_CONSTRUCTOR, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NEED_INDEX_INFO, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION, USE_TREE_TRAVERSAL
 
Constructor Summary
ExtensionExpression(XQueryContext context)
           
 
Method Summary
 void accept(ExpressionVisitor visitor)
          Start traversing the expression tree using the specified ExpressionVisitor.
 void addPragma(Pragma pragma)
           
 void analyze(AnalyzeContextInfo contextInfo)
          Statically analyze the expression and its subexpressions.
 void dump(ExpressionDumper dumper)
          Write a diagnostic dump of the expression to the passed ExpressionDumper.
 Sequence eval(Sequence contextSequence, Item contextItem)
          For every pragma in the list, calls Pragma.before(XQueryContext, Expression) before evaluation.
 int getCardinality()
          The default cardinality is Cardinality.EXACTLY_ONE.
 int getDependencies()
          Returns Dependency.DEFAULT_DEPENDENCIES.
 void resetState(boolean postOptimization)
          Called to inform an expression that it should reset to its initial state.
 int returnsType()
          The static return type of the expression.
 void setContextDocSet(DocumentSet contextSet)
           
 void setExpression(Expression inner)
           
 void setPrimaryAxis(int axis)
           
 
Methods inherited from class org.exist.xquery.AbstractExpression
eval, getASTNode, getContextDocSet, getContextId, getExpressionId, setASTNode
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ExtensionExpression

public ExtensionExpression(XQueryContext context)
Method Detail

setExpression

public void setExpression(Expression inner)

addPragma

public void addPragma(Pragma pragma)

eval

public Sequence eval(Sequence contextSequence,
                     Item contextItem)
              throws XPathException
For every pragma in the list, calls Pragma.before(XQueryContext, Expression) before evaluation. The method then tries to call Pragma.eval(Sequence, Item) on every pragma. If a pragma does not return null for this call, the returned Sequence will become the result of the extension expression. If more than one pragma returns something for eval, an exception will be thrown. If all pragmas return null, we call eval on the original expression and return that.

Specified by:
eval in interface Expression
Specified by:
eval in class AbstractExpression
Parameters:
contextSequence - the current context sequence.
contextItem - a single item, taken from context. This defines the item, the expression should work on.
Throws:
XPathException

returnsType

public int returnsType()
Description copied from interface: Expression
The static return type of the expression. This method should return one of the type constants defined in class Type. If the return type cannot be determined statically, return Type.ITEM.

Specified by:
returnsType in interface Expression
Specified by:
returnsType in class AbstractExpression

analyze

public void analyze(AnalyzeContextInfo contextInfo)
             throws XPathException
Description copied from interface: Expression
Statically analyze the expression and its subexpressions. During the static analysis phase, the query engine can detect unknown variables and some type errors.

Throws:
XPathException

dump

public void dump(ExpressionDumper dumper)
Description copied from interface: Expression
Write a diagnostic dump of the expression to the passed ExpressionDumper.

Parameters:
dumper - the expression dumper to write to

getDependencies

public int getDependencies()
Description copied from class: AbstractExpression
Returns Dependency.DEFAULT_DEPENDENCIES.

Specified by:
getDependencies in interface Expression
Overrides:
getDependencies in class AbstractExpression
Returns:
set of bit-flags
See Also:
Expression.getDependencies()

getCardinality

public int getCardinality()
Description copied from class: AbstractExpression
The default cardinality is Cardinality.EXACTLY_ONE.

Specified by:
getCardinality in interface Expression
Overrides:
getCardinality in class AbstractExpression

setContextDocSet

public void setContextDocSet(DocumentSet contextSet)
Specified by:
setContextDocSet in interface Expression
Overrides:
setContextDocSet in class AbstractExpression

setPrimaryAxis

public void setPrimaryAxis(int axis)
Specified by:
setPrimaryAxis in interface Expression
Overrides:
setPrimaryAxis in class AbstractExpression

resetState

public void resetState(boolean postOptimization)
Description copied from interface: Expression
Called to inform an expression that it should reset to its initial state. All cached data in the expression object should be dropped. For example, the xmldb:document() function calls this method whenever the input document set has changed.

Specified by:
resetState in interface Expression
Overrides:
resetState in class AbstractExpression

accept

public void accept(ExpressionVisitor visitor)
Description copied from interface: Expression
Start traversing the expression tree using the specified ExpressionVisitor.

Specified by:
accept in interface Expression
Overrides:
accept in class AbstractExpression


Copyright (C) Wolfgang Meier. All rights reserved.