eu.fbk.knowledgestore

Class Operation.Sparql

java.lang.Object

eu.fbk.knowledgestore.Operation

eu.fbk.knowledgestore.Operation.Sparql

Enclosing class:

Operation

public abstract static class Operation.Sparql
extends Operation

SPARQL query operation.

This operation evaluates a SPARQL query on the KnowledgeStore SPARQL endpoint. All SPARQL query forms are supported:

• SELECT queries return a Stream of BindingSets (call execTuples());
• CONSTRUCT and DESCRIBE queries return a Stream of Statements (call execTriples());
• ASK queries return a boolean result (call execBoolean()).

The operation can be configured, as usual, by specifying a timeout and supplying optional namespace bindings to be used for parsing the SPARQL expression. In addition, default and named graphs can be specified at the operation level, overriding the corresponding declarations in the FROM and FROM NAMED clauses of the SPARQL query expression.

Nested Class Summary

Nested classes/interfaces inherited from class eu.fbk.knowledgestore.Operation

Operation.Count, Operation.Create, Operation.Delete, Operation.Download, Operation.Match, Operation.Merge, Operation.Retrieve, Operation.Sparql, Operation.SparqlDelete, Operation.SparqlUpdate, Operation.Update, Operation.Upload

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Sparql(Map<String,String> namespaces, String expression, Object... arguments) Creates a new Sparql operation instance (to be used in Session implementations).

Method Summary

Modifier and Type	Method and Description
Operation.Sparql	defaultGraphs(Iterable<org.openrdf.model.URI> defaultGraphs) Sets the optional default graphs for the query, overriding default graphs specified in the FROM clause.
Operation.Sparql	defaultGraphs(org.openrdf.model.URI... defaultGraphs) Sets the optional default graphs for the query, overriding the default graphs specified in the FROM clause.
protected abstract <T> Stream<T>	doExec(Long timeout, Class<T> type, String expression, Set<org.openrdf.model.URI> defaultGraphs, Set<org.openrdf.model.URI> namedGraphs) Implementation method responsible of executing the SPARQL operation.
boolean	execBoolean() Evaluates the query, returning its boolean result; applicable to ASK queries.
Stream<org.openrdf.model.Statement>	execTriples() Evaluates the query, returning a Stream with the resulting Statements; applicable to CONSTRUCT and DESCRIBE queries.
Stream<org.openrdf.query.BindingSet>	execTuples() Evaluates the query, returning a Stream with the resulting BindingSets; applicable to SELECT queries.
Operation.Sparql	namedGraphs(Iterable<org.openrdf.model.URI> namedGraphs) Sets the optional named graphs for the query, overriding named graphs specified in the FROM NAMED clause.
Operation.Sparql	namedGraphs(org.openrdf.model.URI... namedGraphs) Sets the optional named graphs for the query, overriding named graphs specified in the FROM NAMED clause.
Operation.Sparql	namespaces(Map<String,String> namespaces) Sets the optional namespaces for this operation.
Operation.Sparql	timeout(Long timeout) Sets the optional timeout for this operation in milliseconds.

Methods inherited from class java.lang.Object

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

Constructor Detail

Sparql

protected Sparql(Map<String,String> namespaces,
                 String expression,
                 Object... arguments)
          throws ParseException

Creates a new Sparql operation instance (to be used in Session implementations).

Parameters:

namespaces - an immutable map of inherited namespaces, possibly null

expression - the SPARQL query expression, not null and possibly containing $$ placeholders

arguments - the values to assign to $$ placeholders

Throws:

ParseException - in case the query expression is not valid

Method Detail

timeout

public Operation.Sparql timeout(@Nullable
                                Long timeout)

Description copied from class: Operation

Sets the optional timeout for this operation in milliseconds. Passing null or a non-positive value will remove any timeout previously set.

Overrides:

timeout in class Operation

Parameters:

timeout - the timeout; null or non-positive to reset

Returns:

this operation object for call chaining

namespaces

public Operation.Sparql namespaces(@Nullable
                                   Map<String,String> namespaces)

Description copied from class: Operation

Sets the optional namespaces for this operation. Supplied namespaces overrides the namespaces inherited from the Session. Passing null will remove any namespace map previously set on the operation.

Overrides:

namespaces in class Operation

Parameters:

namespaces - the namespace map overriding session namespaces; null to reset

Returns:

this operation object for call chaining

defaultGraphs

public final Operation.Sparql defaultGraphs(@Nullable
                                            org.openrdf.model.URI... defaultGraphs)

Sets the optional default graphs for the query, overriding the default graphs specified in the FROM clause. Passing null will remove any default graph previously set.

Parameters:

defaultGraphs - a vararg array with the non-null URIs of the default graphs, possibly empty; pass null to remove any default graph previously set

Returns:

this operation object for call chaining

defaultGraphs

public final Operation.Sparql defaultGraphs(@Nullable
                                            Iterable<org.openrdf.model.URI> defaultGraphs)

Sets the optional default graphs for the query, overriding default graphs specified in the FROM clause. Passing null will remove any default graph previously set.

Parameters:

defaultGraphs - an Iterable with the non-null URIs of the default graphs, possibly empty; pass null to remove any default graph previously set

Returns:

this operation object for call chaining

namedGraphs

public final Operation.Sparql namedGraphs(@Nullable
                                          org.openrdf.model.URI... namedGraphs)

Sets the optional named graphs for the query, overriding named graphs specified in the FROM NAMED clause. Passing null will remove any named graph previously set.

Parameters:

namedGraphs - a vararg array with the non-null URIs of the named graphs, possibly empty; pass null to remove any named graph previously set

Returns:

this operation object for call chaining

namedGraphs

public final Operation.Sparql namedGraphs(@Nullable
                                          Iterable<org.openrdf.model.URI> namedGraphs)

Sets the optional named graphs for the query, overriding named graphs specified in the FROM NAMED clause. Passing null will remove any named graph previously set.

Parameters:

namedGraphs - an Iterable with the non-null URIs of the named graphs, possibly empty; pass null to remove any named graph previously set

Returns:

this operation object for call chaining

execBoolean

public final boolean execBoolean()
                          throws OperationException

Evaluates the query, returning its boolean result; applicable to ASK queries.

Returns:

the boolean result of the query

Throws:

OperationException - on failure (see possible outcome status codes)

execTriples

public final Stream<org.openrdf.model.Statement> execTriples()
                                                      throws OperationException

Evaluates the query, returning a Stream with the resulting Statements; applicable to CONSTRUCT and DESCRIBE queries.

Returns:

the resulting Stream of Statements

Throws:

OperationException - on failure (see possible outcome status codes)

execTuples

public final Stream<org.openrdf.query.BindingSet> execTuples()
                                                      throws OperationException

Evaluates the query, returning a Stream with the resulting BindingSets; applicable to SELECT queries. After access to the returned Stream, a List<String> with output variables can be obtained by querying the Stream metadata attribute variables.

Returns:

the resulting Stream of BindingSets

Throws:

OperationException - on failure (see possible outcome status codes)

doExec

protected abstract <T> Stream<T> doExec(@Nullable
                                        Long timeout,
                                        Class<T> type,
                                        String expression,
                                        @Nullable
                                        Set<org.openrdf.model.URI> defaultGraphs,
                                        @Nullable
                                        Set<org.openrdf.model.URI> namedGraphs)
                                 throws OperationException

Implementation method responsible of executing the SPARQL operation.

Type Parameters:

T - the type of result elements

Parameters:

timeout - the optional timeout for the operation; null if there is no timeout

type - the expected type of elements for the resulting Stream; either Statement, BindingSet or Boolean

expression - the SPARQL query expression

defaultGraphs - the optional set of default graphs overriding the ones possibly specified in the FROM query clause; if null, no override should take place

namedGraphs - the optional set of named graphs overriding the ones possibly specified in the FROM NAMED query clause; if null, no override should take place

Returns:

a Stream with the result of the query

Throws:

OperationException - in case of failure (see possible outcome status codes)