Running Tentris Using Java

Requirements

• Java>=11
• org.eclipse.rdf4j>=5.3.0 (last tested with 5.3.2)

Install

Add rdf4j as dependency to your Java project (e.g. in the pom.xml for Maven).

Getting Started

Compatibility with rdf4j is currently limited to the SPARQLRepository HTTP-connector.

import org.eclipse.rdf4j.repository.sparql.SPARQLRepository;
import org.eclipse.rdf4j.repository.RepositoryConnection;
import org.eclipse.rdf4j.query.TupleQuery;
import org.eclipse.rdf4j.query.TupleQueryResult;
import org.eclipse.rdf4j.query.BindingSet;

public class Main {
    public static void main(String[] args) {
        String queryUrl = "https://dbpedia.data.dice-research.org/sparql";

        // Note: updates are also supported (on servers that have them enabled).
        SPARQLRepository repo = new SPARQLRepository(queryUrl);

        repo.init();

        try (RepositoryConnection conn = repo.getConnection()) {
            TupleQuery query = conn.prepareTupleQuery("SELECT * WHERE { ?s ?p ?o } LIMIT 10");
            try (TupleQueryResult result = query.evaluate()) {
                while (result.hasNext()) {
                    BindingSet solution = result.next();
                    System.out.printf("%s %s %s .\n", solution.getValue("s"), solution.getValue("p"), solution.getValue("o"));
                }
            }
        } finally {
            repo.shutDown();
        }
    }
}

For more information about setting up a disk-based instance of Tentris, please refer to the chapter Binary.

Remote Login

To log into a remote instance of Tentris that has authentication enabled, the following can be used.

import org.eclipse.rdf4j.query.BindingSet;
import org.eclipse.rdf4j.query.TupleQuery;
import org.eclipse.rdf4j.query.TupleQueryResult;
import org.eclipse.rdf4j.repository.RepositoryConnection;
import org.eclipse.rdf4j.repository.sparql.SPARQLRepository;

import java.io.IOException;
import java.net.CookieManager;
import java.net.HttpCookie;
import java.net.URI;
import java.net.URLEncoder;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        String baseUrl = "https://remote-server-with-auth.example.com";

        // Note: updates are also supported (on servers that have them enabled).
        SPARQLRepository repo = new SPARQLRepository(baseUrl + "/sparql");

        String cookie = login(baseUrl, "my-username", "my-password");

        // This replaces setUsernameAndPassword()
        Map<String, String> headers = new HashMap<>();
        headers.put("Cookie", cookie);
        repo.setAdditionalHttpHeaders(headers);

        repo.init();

        try (RepositoryConnection conn = repo.getConnection()) {
            TupleQuery query = conn.prepareTupleQuery("SELECT * WHERE { ?s ?p ?o } LIMIT 10");
            try (TupleQueryResult result = query.evaluate()) {
                while (result.hasNext()) {
                    BindingSet solution = result.next();
                    System.out.printf("%s %s %s .\n", solution.getValue("s"), solution.getValue("p"), solution.getValue("o"));
                }
            }
        } finally {
            repo.shutDown();
        }
    }

    private static String login(String baseUrl, String username, String password) throws IOException, InterruptedException {
        CookieManager cm = new CookieManager();
        HttpClient client = HttpClient.newBuilder().cookieHandler(cm).build();

        String formData = String.format("username=%s&password=%s", URLEncoder.encode(username, StandardCharsets.UTF_8), URLEncoder.encode(password, StandardCharsets.UTF_8));

        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(baseUrl + "/login"))
                .header("Content-Type", "application/x-www-form-urlencoded")
                .POST(HttpRequest.BodyPublishers.ofString(formData))
                .build();

        client.send(request, HttpResponse.BodyHandlers.discarding());

        HttpCookie cookie = cm.getCookieStore().getCookies().stream().filter(c -> c.getName().equals("tentris")).findFirst().get();
        return String.format("%s=%s", cookie.getName(), cookie.getValue());
    }
}