public interface ValueMaker
Typical implementations are Attribute
(describing the set
of strings contained in one database column), Pattern
(describing the set of strings that is obtained by sticking
the values of several database fields into a string pattern),
and BlankNodeID
(similar).
There are several other ValueSources that modify the behaviour
of another underlying ValueSource, implementing the Decorator
pattern. This includes TranslationTable
.TranslatingValueSource
(translates values using a translation table or translation class)
and the various value restrictions (@link RegexRestriction et. al.).
ValueSources are used by NodeMakers. A node maker wraps the strings into Jena nodes, thus creating a description of a set of RDF nodes.
Modifier and Type | Field and Description |
---|---|
static ValueMaker |
NULL
A value maker that never produces a value.
|
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
ProjectionSpec s 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.
|
static final ValueMaker NULL
Expression valueExpression(String value)
Expression.FALSE
if this
value maker is incapable of producing the value.value
- A valueSet<ProjectionSpec> projectionSpecs()
ProjectionSpec
s containing data necessary
for this ValueSource.ProjectionSpec
sString makeValue(ResultRow row)
row
- the database rowvoid describeSelf(NodeSetFilter c)
ValueMaker renameAttributes(ColumnRenamer renamer)