be.ugent.rml.access.AccessFactory Maven / Gradle / Ivy
package be.ugent.rml.access;
import be.ugent.rml.NAMESPACES;
import be.ugent.rml.Utils;
import be.ugent.rml.records.SPARQLResultFormat;
import be.ugent.rml.store.QuadStore;
import be.ugent.rml.term.Literal;
import be.ugent.rml.term.NamedNode;
import be.ugent.rml.term.Term;
import org.apache.commons.lang.NotImplementedException;
import java.util.List;
import static be.ugent.rml.Utils.isRemoteFile;
/**
* This class creates Access instances.
*/
public class AccessFactory {
// The path used when local paths are not absolute.
private String basePath;
/**
* The constructor of the AccessFactory.
* @param basePath the base path for the local file system.
*/
public AccessFactory(String basePath) {
this.basePath = basePath;
}
/**
* This method returns an Access instance based on the RML rules in rmlStore.
* @param logicalSource the Logical Source for which the Access needs to be created.
* @param rmlStore a QuadStore with RML rules.
* @return an Access instance based on the RML rules in rmlStore.
*/
public Access getAccess(Term logicalSource, QuadStore rmlStore) {
List sources = Utils.getObjectsFromQuads(rmlStore.getQuads(logicalSource, new NamedNode(NAMESPACES.RML + "source"), null));
Access access = null;
// check if at least one source is available.
if (!sources.isEmpty()) {
Term source = sources.get(0);
// if we are dealing with a literal,
// then it's either a local or remote file.
if (sources.get(0) instanceof Literal) {
String value = sources.get(0).getValue();
if (isRemoteFile(value)) {
access = new RemoteFileAccess(value);
} else {
access = new LocalFileAccess(value, this.basePath);
}
} else {
// if not a literal, then we are dealing with a more complex description.
List sourceType = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.RDF + "type"), null));
switch(sourceType.get(0).getValue()) {
case NAMESPACES.D2RQ + "Database": // RDBs
access = getRDBAccess(rmlStore, source, logicalSource);
break;
case NAMESPACES.SD + "Service": // SPARQL
// Check if SPARQL Endpoint is given
List endpoint = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.SD + "endpoint"),
null));
if (endpoint.isEmpty()) {
throw new Error("No SPARQL endpoint found.");
}
// Get query
List query = Utils.getObjectsFromQuads(rmlStore.getQuads(logicalSource, new NamedNode(NAMESPACES.RML + "query"), null));
if (query.isEmpty()) {
throw new Error("No SPARQL query found");
}
List referenceFormulations = Utils.getObjectsFromQuads(rmlStore.getQuads(logicalSource, new NamedNode(NAMESPACES.RML + "referenceFormulation"), null));
// Get result format
List resultFormatObject = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.SD + "resultFormat"), null));
SPARQLResultFormat resultFormat = getSPARQLResultFormat(resultFormatObject, referenceFormulations);
String queryString = query.get(0).getValue().replaceAll("[\r\n]+", " ").trim();
access = new SPARQLEndpointAccess(resultFormat.getContentType(), endpoint.get(0).getValue(), queryString);;
break;
case NAMESPACES.CSVW + "Table": // CSVW
List urls = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.CSVW + "url"), null));
if (urls.isEmpty()) {
throw new Error("No url found for the CSVW Table");
}
String value = urls.get(0).getValue();
if (isRemoteFile(value)) {
access = new RemoteFileAccess(value);
} else {
access = new LocalFileAccess(value, this.basePath);
}
break;
default:
throw new NotImplementedException();
}
}
return access;
} else {
throw new Error("The Logical Source does not have a source.");
}
}
/**
* This method returns an RDB Access instance for the RML rules in rmlStore.
* @param rmlStore a QuadStore with RML rules.
* @param source the object of rml:source, dependent on the Logical Source.
* @param logicalSource the Logical Source for which the Access instance need to be created.
* @return an RDB Access instance for the RML rules in rmlStore.
*/
private RDBAccess getRDBAccess(QuadStore rmlStore, Term source, Term logicalSource) {
// - Table
List tables = Utils.getObjectsFromQuads(rmlStore.getQuads(logicalSource, new NamedNode(NAMESPACES.RR + "tableName"), null));
// Retrieve database information from source object
// - Driver URL
List driverObject = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.D2RQ + "jdbcDriver"), null));
if (driverObject.isEmpty()) {
throw new Error("The database source object " + source + " does not include a driver.");
}
DatabaseType database = DatabaseType.getDBtype(driverObject.get(0).getValue());
// - DSN
List dsnObject = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.D2RQ + "jdbcDSN"), null));
if(dsnObject.isEmpty()) {
throw new Error("The database source object " + source + " does not include a Data Source Name.");
}
String dsn = dsnObject.get(0).getValue();
dsn = dsn.substring(dsn.indexOf("//") + 2);
// - SQL query
String query;
List queryObject = Utils.getObjectsFromQuads(rmlStore.getQuads(logicalSource, new NamedNode(NAMESPACES.RML + "query"), null));
if (queryObject.isEmpty()) {
if (tables.isEmpty()) {
// TODO better message (include Triples Map somewhere)
throw new Error("The Logical Source does not include a SQL query nor a target table.");
} else if (tables.get(0).getValue().equals("") || tables.get(0).getValue().equals("\"\"")) {
throw new Error("The table name of a database should not be empty.");
} else {
query = "SELECT * FROM " + tables.get(0).getValue();
}
} else {
query = queryObject.get(0).getValue();
}
// - Username
List usernameObject = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.D2RQ + "username"), null));
if (usernameObject.isEmpty()) {
throw new Error("The database source object " + source + " does not include a username.");
}
String username = usernameObject.get(0).getValue();
// - Password
String password = ""; // No password is the default.
List passwordObject = Utils.getObjectsFromQuads(rmlStore.getQuads(source, new NamedNode(NAMESPACES.D2RQ + "password"), null));
if (!passwordObject.isEmpty()) {
password = passwordObject.get(0).getValue();
}
return new RDBAccess(dsn, database, username, password, query, "text/csv");
}
/**
* This method returns a SPARQLResultFormat based on the result formats and reference formulations.
* @param resultFormats the result formats used to determine the SPARQLResultFormat.
* @param referenceFormulations the reference formulations used to to determine the SPARQLResultFormat.
* @return a SPARQLResultFormat.
*/
private SPARQLResultFormat getSPARQLResultFormat(List resultFormats, List referenceFormulations) {
if (resultFormats.isEmpty() && referenceFormulations.isEmpty()) { // This will never be called atm but may come in handy later
throw new Error("Please specify the sd:resultFormat of the SPARQL endpoint or a rml:referenceFormulation.");
} else if (referenceFormulations.isEmpty()) {
for (SPARQLResultFormat format: SPARQLResultFormat.values()) {
if (resultFormats.get(0).getValue().equals(format.getUri())) {
return format;
}
}
// No matching SPARQLResultFormat found
throw new Error("Unsupported sd:resultFormat: " + resultFormats.get(0));
} else if (resultFormats.isEmpty()) {
for (SPARQLResultFormat format: SPARQLResultFormat.values()) {
if (format.getReferenceFormulations().contains(referenceFormulations.get(0).getValue())) {
return format;
}
}
// No matching SPARQLResultFormat found
throw new Error("Unsupported rml:referenceFormulation for a SPARQL source.");
} else {
for (SPARQLResultFormat format : SPARQLResultFormat.values()) {
if (resultFormats.get(0).getValue().equals(format.getUri())
&& format.getReferenceFormulations().contains(referenceFormulations.get(0).getValue())) {
return format;
}
}
throw new Error("Format specified in sd:resultFormat doesn't match the format specified in rml:referenceFormulation.");
}
}
}
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