org.openrdf.query.algebra.evaluation.federation

Class SPARQLFederatedService

java.lang.Object

org.openrdf.query.algebra.evaluation.federation.SPARQLFederatedService

All Implemented Interfaces:

FederatedService

public class SPARQLFederatedService
extends Object
implements FederatedService

Federated Service wrapping the SPARQLRepository to communicate with a SPARQL endpoint.

Author:

Andreas Schwarte

Nested Class Summary

Nested classes/interfaces inherited from interface org.openrdf.query.algebra.evaluation.federation.FederatedService

FederatedService.QueryType

Field Summary

Fields

Modifier and Type	Field and Description
protected RepositoryConnection	conn
protected SPARQLRepository	rep

Constructor Summary

Constructors

Constructor and Description
SPARQLFederatedService(String serviceUrl)

Method Summary

Methods

Modifier and Type	Method and Description
protected static StringBuilder	appendLiteral(StringBuilder sb, Literal lit) Append the literal to the stringbuilder: "myLiteral"^^
protected static StringBuilder	appendURI(StringBuilder sb, URI uri) Append the uri to the stringbuilder, i.e.
protected StringBuilder	appendValueAsString(StringBuilder sb, Value value)
CloseableIteration<BindingSet,QueryEvaluationException>	evaluate(Service service, CloseableIteration<BindingSet,QueryEvaluationException> bindings, String baseUri) Evaluate the provided SPARQL query at this federated service, possibilities for vectored evaluation.
CloseableIteration<BindingSet,QueryEvaluationException>	evaluate(String sparqlQueryString, BindingSet bindings, String baseUri, FederatedService.QueryType type, Service service) Evaluate the provided sparqlQueryString at the initialized SPARQLRepository of this FederatedService.
protected CloseableIteration<BindingSet,QueryEvaluationException>	evaluateInternal(Service service, CloseableIteration<BindingSet,QueryEvaluationException> bindings, String baseUri) Evaluate the SPARQL query that can be constructed from the SERVICE node at the initialized SPARQLRepository of this FederatedService.
protected RepositoryConnection	getConnection()
void	initialize() Method to perform any initializations, invoked after construction.
void	shutdown() Method to perform any shutDown code, invoked at unregistering.

Methods inherited from class java.lang.Object

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

Field Detail

rep

protected final SPARQLRepository rep

conn

protected RepositoryConnection conn

Constructor Detail

SPARQLFederatedService

public SPARQLFederatedService(String serviceUrl)

Parameters:

serviceUrl - the serviceUrl use to initialize the inner SPARQLRepository

Method Detail

evaluate

public CloseableIteration<BindingSet,QueryEvaluationException> evaluate(String sparqlQueryString,
                                                               BindingSet bindings,
                                                               String baseUri,
                                                               FederatedService.QueryType type,
                                                               Service service)
                                                                 throws QueryEvaluationException

Evaluate the provided sparqlQueryString at the initialized SPARQLRepository of this FederatedService. Dependent on the type (ASK/SELECT) different evaluation is necessary: SELECT: insert bindings into SELECT query and evaluate ASK: insert bindings, send ask query and return final result

Specified by:

evaluate in interface FederatedService

Parameters:

sparqlQueryString - a SPARQL query (either SELECT or ASK, compare type parameter)

bindings - the bindings serving as additional constraints

type - the FederatedService.QueryType, either ASK or SELECT

service - the reference to the service node, contains additional meta information (vars, prefixes)

Returns:

an iteration over the results of the query

Throws:

QueryEvaluationException

evaluate

public CloseableIteration<BindingSet,QueryEvaluationException> evaluate(Service service,
                                                               CloseableIteration<BindingSet,QueryEvaluationException> bindings,
                                                               String baseUri)
                                                                 throws QueryEvaluationException

Description copied from interface: FederatedService

Evaluate the provided SPARQL query at this federated service, possibilities for vectored evaluation.

Contracts:

• The original bindings need to be inserted into the result, e.g. via InsertBindingSetCursor.
• SILENT service must be dealt with in the method

Compare SPARQLFederatedService for a reference implementation

Specified by:

evaluate in interface FederatedService

Parameters:

service - the reference to the service node, contains information to construct the query

bindings - the bindings serving as additional constraints (for vectored evaluation)

baseUri - the baseUri

Returns:

the result of evaluating the query using bindings as constraints, the original bindings need to be inserted into the results!

Throws:

QueryEvaluationException

evaluateInternal

protected CloseableIteration<BindingSet,QueryEvaluationException> evaluateInternal(Service service,
                                                                       CloseableIteration<BindingSet,QueryEvaluationException> bindings,
                                                                       String baseUri)
                                                                            throws QueryEvaluationException

Evaluate the SPARQL query that can be constructed from the SERVICE node at the initialized SPARQLRepository of this FederatedService. Use specified bindings as constraints to the query. Try to evaluate using BINDINGS clause, if this yields an exception fall back to the naive implementation. This method deals with SILENT SERVICEs.

Throws:

QueryEvaluationException

initialize

public void initialize()
                throws RepositoryException

Description copied from interface: FederatedService

Method to perform any initializations, invoked after construction.

Specified by:

initialize in interface FederatedService

Throws:

RepositoryException

shutdown

public void shutdown()
              throws RepositoryException

Description copied from interface: FederatedService

Method to perform any shutDown code, invoked at unregistering.

Specified by:

shutdown in interface FederatedService

Throws:

RepositoryException

getConnection

protected RepositoryConnection getConnection()
                                      throws RepositoryException

Throws:

RepositoryException

appendValueAsString

protected StringBuilder appendValueAsString(StringBuilder sb,
                                Value value)

appendURI

protected static StringBuilder appendURI(StringBuilder sb,
                      URI uri)

Append the uri to the stringbuilder, i.e. .

Parameters:

sb -

uri -

Returns:

the StringBuilder, for convenience

appendLiteral

protected static StringBuilder appendLiteral(StringBuilder sb,
                          Literal lit)

Append the literal to the stringbuilder: "myLiteral"^^

Parameters:

sb -

lit -

Returns:

the StringBuilder, for convenience