org.geotools.feature.visitor

Class GroupByVisitor

Object

GroupByVisitor

All Implemented Interfaces:

FeatureAttributeVisitor, FeatureCalc, FeatureVisitor

public class GroupByVisitor
extends Object
implements FeatureCalc, FeatureAttributeVisitor

Group features by one or several attributes and applies an aggregator visitor to each group.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GroupByVisitor.GroupByRawResult Helper class that should be used by optimizations to set the results.
static class	GroupByVisitor.GroupByResult This class implements the feature calculation result of the group by visitor.

Constructor Summary

Constructors

Constructor and Description
GroupByVisitor(Aggregate aggregateVisitor, Expression expression, List<Expression> groupByAttributes, ProgressListener progressListener)

Method Summary

Modifier and Type	Method and Description
FeatureVisitor	getAggregateVisitor()
Expression	getExpression()
List<Expression>	getExpressions() List of expressions used by visitor.
List<Expression>	getGroupByAttributes()
CalcResult	getResult() This method computes and returns the group by visitor result.
void	setValue(List<GroupByVisitor.GroupByRawResult> value) Methods that allow optimizations to directly set the group by visitor result instead of computing it visiting all the features.
void	visit(Feature feature) Visit the provided feature.
boolean	wasOptimized()
boolean	wasVisited()

Methods inherited from class Object

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

Constructor Detail

GroupByVisitor

public GroupByVisitor(Aggregate aggregateVisitor,
                      Expression expression,
                      List<Expression> groupByAttributes,
                      ProgressListener progressListener)

Method Detail

wasOptimized

public boolean wasOptimized()

wasVisited

public boolean wasVisited()

getResult

public CalcResult getResult()

This method computes and returns the group by visitor result. If the computation was optimized the optimization result is returned otherwise the result is computed in memory. If for some reason an optimization result exists and there are visited features, an in memory computation is performed and is merged with the existing optimization results.

Specified by:

getResult in interface FeatureCalc

Returns:

group by visitor result

visit

public void visit(Feature feature)

Description copied from interface: FeatureVisitor

Visit the provided feature.

Please consult the documentation for the FeatureCollection you are visiting to learn more - the provided feature may be invalid, or read only.

Specified by:

visit in interface FeatureVisitor

getExpression

public Expression getExpression()

getAggregateVisitor

public FeatureVisitor getAggregateVisitor()

getGroupByAttributes

public List<Expression> getGroupByAttributes()

setValue

public void setValue(List<GroupByVisitor.GroupByRawResult> value)

Methods that allow optimizations to directly set the group by visitor result instead of computing it visiting all the features. Aggregate visitor results are wrapped with the appropriate feature calculation type.

Parameters:

value - the group by visitor result

getExpressions

public List<Expression> getExpressions()

Description copied from interface: FeatureAttributeVisitor

List of expressions used by visitor.

Specified by:

getExpressions in interface FeatureAttributeVisitor