org.exist.xquery
Class SimpleStep

java.lang.Object
  extended byorg.exist.xquery.AbstractExpression
      extended byorg.exist.xquery.Step
          extended byorg.exist.xquery.SimpleStep
All Implemented Interfaces:
Expression

public class SimpleStep
extends Step

Represents a primary expression in a simple path step like foo//$x. The class is mainly used to wrap variable references inside a path expression.

Author:
Wolfgang Meier (wolfgang@exist-db.org)

Field Summary
 
Fields inherited from interface org.exist.xquery.Expression
DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION
 
Constructor Summary
SimpleStep(XQueryContext context, int axis, Expression expression)
           
 
Method Summary
 void analyze(AnalyzeContextInfo contextInfo)
          Statically analyze the expression and its subexpressions.
 Sequence eval(Sequence contextSequence, Item contextItem)
          Evaluate the expression represented by this object.
 void resetState()
          Called to inform an expression that it should reset to its initial state.
 void setContextDocSet(DocumentSet contextSet)
           
 void setPrimaryAxis(int axis)
           
 
Methods inherited from class org.exist.xquery.Step
addPredicate, dump, getAxis, getCardinality, returnsType, setAxis, setTest, toString
 
Methods inherited from class org.exist.xquery.AbstractExpression
accept, eval, getASTNode, getContextDocSet, getContextId, getDependencies, getExpressionId, setASTNode
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

SimpleStep

public SimpleStep(XQueryContext context,
                  int axis,
                  Expression expression)
Parameters:
context -
axis -
Method Detail

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.

Specified by:
analyze in interface Expression
Overrides:
analyze in class Step
Throws:
XPathException

eval

public Sequence eval(Sequence contextSequence,
                     Item contextItem)
              throws XPathException
Description copied from interface: Expression
Evaluate the expression represented by this object. Depending on the context in which this expression is executed, either the context sequence, the context item or both of them may be set. An implementing class should know how to handle this. The general contract is as follows: if the Dependency.CONTEXT_ITEM bit is set in the bit field returned by Expression.getDependencies(), the eval method will be called once for every item in the context sequence. The contextItem parameter will be set to the current item. Otherwise, the eval method will only be called once for the whole context sequence and contextItem will be null. eXist tries to process the entire context set in one, single step whenever possible. Thus, most classes only expect context to contain a list of nodes which represents the current context of the expression. The position() function in XPath is an example for an expression, which requires both, context sequence and context item to be set. The context sequence might be a node set, a sequence of atomic values or a single node or atomic value.

Specified by:
eval in interface Expression
Specified by:
eval in class Step
Throws:
XPathException

resetState

public void resetState()
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 document() function calls this method whenever the input document set has changed.

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

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 Step


Copyright (C) Wolfgang Meier. All rights reserved.