org.exist.xquery
Class AbstractExpression

java.lang.Object
  org.exist.xquery.AbstractExpression

All Implemented Interfaces:

Expression

Direct Known Subclasses:

AtomicToString, Atomize, BindingExpression, CastableExpression, CastExpression, CombiningExpression, ConditionalExpression, DynamicCardinalityCheck, DynamicNameCheck, DynamicTypeCheck, ExtensionExpression, FilteredExpression, InstanceOfExpression, LiteralValue, Modification, NodeConstructor, PathExpr, Step, TreatAsExpression, TypeswitchExpression, UntypedValueCheck, VariableDeclaration, VariableReference

public abstract class AbstractExpression
extends Object
implements Expression

Field Summary

Fields inherited from interface org.exist.xquery.Expression

DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NEED_INDEX_INFO, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION

Constructor Summary

AbstractExpression(XQueryContext context)

Method Summary

void	accept(ExpressionVisitor visitor) Start traversing the expression tree using the specified ExpressionVisitor.
Sequence	eval(Sequence contextSequence) Evaluate the expression represented by this object.
abstract Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
XQueryAST	getASTNode() Returns the XQueryAST node from which this expression has been constructed by the parser.
int	getCardinality() The default cardinality is Cardinality.EXACTLY_ONE.
DocumentSet	getContextDocSet()
int	getContextId()
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
int	getExpressionId() Returns an id which uniquely identifies this expression within the compiled expression tree of the query.
void	resetState() Called to inform an expression that it should reset to its initial state.
abstract int	returnsType() The static return type of the expression.
void	setASTNode(XQueryAST ast)
void	setContextDocSet(DocumentSet contextSet)
void	setPrimaryAxis(int axis)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.exist.xquery.Expression

analyze, dump

Constructor Detail

AbstractExpression

public AbstractExpression(XQueryContext context)

Method Detail

getExpressionId

public int getExpressionId()

Description copied from interface: Expression

Returns an id which uniquely identifies this expression within the compiled expression tree of the query.

Specified by:

getExpressionId in interface Expression

Returns:

unique id or Expression.EXPRESSION_ID_INVALID

getContextId

public int getContextId()

Specified by:

getContextId in interface Expression

eval

public Sequence eval(Sequence contextSequence)
              throws XPathException

Description copied from interface: Expression

Evaluate the expression represented by this object. An overloaded method which just passes the context sequence depending on the expression context.

Specified by:

eval in interface Expression

Throws:

XPathException

eval

public abstract 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

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 abstract 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

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

getCardinality

public int getCardinality()

The default cardinality is Cardinality.EXACTLY_ONE.

Specified by:

getCardinality in interface Expression

getDependencies

public int getDependencies()

Returns Dependency.DEFAULT_DEPENDENCIES.

Specified by:

getDependencies in interface Expression

Returns:

set of bit-flags

See Also:

Expression.getDependencies()

setPrimaryAxis

public void setPrimaryAxis(int axis)

Specified by:

setPrimaryAxis in interface Expression

setContextDocSet

public void setContextDocSet(DocumentSet contextSet)

Specified by:

setContextDocSet in interface Expression

getContextDocSet

public DocumentSet getContextDocSet()

Specified by:

getContextDocSet in interface Expression

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

setASTNode

public void setASTNode(XQueryAST ast)

Specified by:

setASTNode in interface Expression

getASTNode

public XQueryAST getASTNode()

Description copied from interface: Expression

Returns the XQueryAST node from which this expression has been constructed by the parser. This node contains location information (line number and column) important for error reports.

Specified by:

getASTNode in interface Expression

Returns:

XQueryAST node