de.fuberlin.wiwiss.d2rq.values

Class ConstantValueMaker

java.lang.Object

de.fuberlin.wiwiss.d2rq.values.ConstantValueMaker

All Implemented Interfaces:

ValueMaker

public class ConstantValueMaker
extends Object
implements ValueMaker

A pseudo value maker that produces a constant value regardless of the underlying relation. Note that FixedNodeMaker doesn't use an instance of this class, but handles the constantness of its underlying values directly. This class is only used where we need to produce constant strings, rather than constant RDF nodes.

Author:

Richard Cyganiak (richard@cyganiak.de)

Field Summary

Fields inherited from interface de.fuberlin.wiwiss.d2rq.values.ValueMaker

NULL

Constructor Summary

Constructors

Constructor and Description
ConstantValueMaker(String constant)

Method Summary

Methods

Modifier and Type	Method and Description
void	describeSelf(NodeSetFilter c)
String	makeValue(ResultRow row) Retrieves a value from a database row according to some rule or pattern.
List<OrderSpec>	orderSpecs(boolean ascending)
Set<ProjectionSpec>	projectionSpecs() Returns a set of all ProjectionSpecs containing data necessary for this ValueSource.
ValueMaker	renameAttributes(ColumnRenamer renamer)
Expression	valueExpression(String value) A SQL expression that selects only rows where this value maker produces the specified value.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConstantValueMaker

public ConstantValueMaker(String constant)

Method Detail

valueExpression

public Expression valueExpression(String value)

Description copied from interface: ValueMaker

A SQL expression that selects only rows where this value maker produces the specified value. Expression.FALSE if this value maker is incapable of producing the value.

Specified by:

valueExpression in interface ValueMaker

Parameters:

value - A value

Returns:

An expression that selects rows that produce this value

projectionSpecs

public Set<ProjectionSpec> projectionSpecs()

Description copied from interface: ValueMaker

Returns a set of all ProjectionSpecs containing data necessary for this ValueSource.

Specified by:

projectionSpecs in interface ValueMaker

Returns:

a set of ProjectionSpecs

makeValue

public String makeValue(ResultRow row)

Description copied from interface: ValueMaker

Retrieves a value from a database row according to some rule or pattern.

Specified by:

makeValue in interface ValueMaker

Parameters:

row - the database row

Returns:

a value created from the row

describeSelf

public void describeSelf(NodeSetFilter c)

Specified by:

describeSelf in interface ValueMaker

renameAttributes

public ValueMaker renameAttributes(ColumnRenamer renamer)

Specified by:

renameAttributes in interface ValueMaker

orderSpecs

public List<OrderSpec> orderSpecs(boolean ascending)

Specified by:

orderSpecs in interface ValueMaker