Hello world in GraphDB

The following program opens a connection to a repository, evaluates a SPARQL query and prints the result. The example uses an embedded GraphDB instance but it can easily be modified to connect to a remote repository. See also Embedded GraphDB.

In order to run the example program, you need to build from the appropriate .pom file:

mvn install

Followed by running the resultant .jar file:

java -jar dev-examples-1.0-SNAPSHOT.jar
package com.ontotext.graphdb.example.app.hello;

import com.ontotext.graphdb.example.util.EmbeddedGraphDB;
import org.openrdf.model.Value;
import org.openrdf.query.*;
import org.openrdf.repository.RepositoryConnection;

/**
 * Hello World app for GraphDB
 */
public class HelloWorld {
    public void hello() throws Exception {
        // Open connection to a new temporary repository
        // (ruleset is irrelevant for this example)
        RepositoryConnection connection = EmbeddedGraphDB.openConnectionToTemporaryRepository("rdfs");

        /* Alternative: connect to a remote repository

        // Abstract representation of a remote repository accessible over HTTP
        HTTPRepository repository = new HTTPRepository("http://localhost:8080/graphdb/repositories/myrepo");

        // Separate connection to a repository
        RepositoryConnection connection = repository.getConnection();

        */

        try {
            // Preparing a SELECT query for later evaluation
            TupleQuery tupleQuery = connection.prepareTupleQuery(QueryLanguage.SPARQL,
                    "SELECT ?x WHERE {" +
                            "BIND('Hello world!' as ?x)" +
                            "}");

            // Evaluating a prepared query returns an iterator-like object
            // that can be traversed with the methods hasNext() and next()
            TupleQueryResult tupleQueryResult = tupleQuery.evaluate();
            while (tupleQueryResult.hasNext()) {
                // Each result is represented by a BindingSet, which corresponds to a result row
                BindingSet bindingSet = tupleQueryResult.next();

                // Each BindingSet contains one or more Bindings
                for (Binding binding : bindingSet) {
                    // Each Binding contains the variable name and the value for this result row
                    String name = binding.getName();
                    Value value = binding.getValue();

                    System.out.println(name + " = " + value);
                }

                // Bindings can also be accessed explicitly by variable name
                //Binding binding = bindingSet.getBinding("x");
            }

            // Once we are done with a particular result we need to close it
            tupleQueryResult.close();

            // Doing more with the same connection object
            // ...
        } finally {
            // It is best to close the connection in a finally block
            connection.close();
        }
    }

    public static void main(String[] args) throws Exception {
        new HelloWorld().hello();
    }
}