// Downloaded apache-jena-4.4.0.tar.gz from https://jena.apache.org/download/ and extracted it.
// cheeses-0.1.ttl is also taken from the downloaded archive.
// Run with: java -classpath apache-jena-4.4.0/lib/*:. SimpleSparqlServer.java
import java.io.*;
import com.sun.net.httpserver.*;
import org.apache.jena.riot.*;
import static java.nio.charset.StandardCharsets.UTF_8;
class SimpleSparqlServer {
public static void main(String[] args) throws InterruptedException, IOException {
System.out.println("Opening database...");
var dir = "data";
var dataset = org.apache.jena.tdb2.TDB2Factory.connectDataset(dir);
System.err.println("Loading cheeses-0.1.ttl...");
dataset.executeWrite(() -> {
var model = dataset.getDefaultModel();
try {
model.read(new FileInputStream("cheeses-0.1.ttl"), null, "TTL");
} catch (FileNotFoundException e) {
System.err.println(e);
}
model.close();
});
System.out.println("Starting webserver...");
var server = HttpServer.create(new java.net.InetSocketAddress("localhost", 8080), 0);
server.createContext("/", con -> {
// GET / → show website with query form
con.getResponseHeaders().set("Content-Type", "text/html; charset=utf-8");
con.sendResponseHeaders(200, 0);
con.getResponseBody().write("""
SPARQL Webserver
""".getBytes(UTF_8));
con.close();
});
server.createContext("/query", con -> {
// POST /query { "query": "..." } → query result as expanded JSON-LD
dataset.executeRead(() -> {
var body = org.apache.jena.atlas.json.JSON.parse(con.getRequestBody());
var queryCode = body.getString("query");
try {
try (var query = org.apache.jena.query.QueryExecution.create(queryCode, dataset)) {
var model = query.execConstruct();
con.sendResponseHeaders(200, 0);
RDFWriter.create(model).format(RDFFormat.JSONLD_EXPAND_PRETTY).output(con.getResponseBody());
} catch (org.apache.jena.query.QueryParseException e) { // thrown on SPARQL syntax error
con.getResponseHeaders().set("Content-Type", "text/plain");
con.sendResponseHeaders(500, 0);
con.getResponseBody().write(e.getMessage().getBytes(UTF_8));
} finally {
con.close();
}
} catch (IOException ignored) {
}
});
});
server.start();
System.out.println("Ready, accepting connections :)");
}
}