rahular.github.io

I have been trying to learn the Titan graph DB for a few weeks now. The documentation, though comprehensive, is scattered in GitHub and on their site. Since it is in active development, the versions keep changing and the documentation for the older versions sometimes become obsolete.

You can find the documentation of their latest release here

After a few nights of sleepless research, I finally figured out how to use Titan in Java. So here is how you can quickly start writing programs with Titan as your DB.

Note: I am using Eclipse Luna on Ubuntu 14.04.

1. Download Titan. Link
2. Extract it anywhere. You will find a folder named lib which will contain all the dependency JARs. Make note of it’s path.
3. Create a project in Eclipse and go to properties -> Java Build Path
4. Click on Add library -> User library -> User libraries
5. Click on New and give the library a name. I gave titan-java
6. An empty User library should have been created if everything went well
7. Click on Add external JARs and navigate to the lib folder (we made note of this in Step 2)
8. Add all the JARs and finish.

Now everything is set and we are good to go. The API is pretty straight-forward and since Titan adheres to Tinkerpop’s Blueprints API, the documentation is available readily all over the web.

Below you can see the starter code I wrote which will:

• open the graph
• add some data if it is empty
• print the names of the vertices
• close the graph

Note: You will have to create a folder named db in the project’s root folder. This is where Titan creates the database.

The code uses Berkeley DB as the index backend. You can change it with anything you want. Titan supports Cassandra, HBase, etc.

import com.thinkaurelius.titan.core.TitanFactory;
import com.thinkaurelius.titan.core.TitanGraph;
import com.tinkerpop.blueprints.Edge;
import com.tinkerpop.blueprints.Vertex;

public class Titan {

	private TitanGraph graph;
	private boolean isGraphOpen;
	
	public Titan() {
	}

	public void openGraph() {
		if(isGraphOpen) {
			System.out.println("Graph is already open.");
			return;
		}
		graph = TitanFactory.build()
				.set("storage.backend", "berkeleyje")
				.set("storage.directory", "./db").open();
		isGraphOpen = true;
	}
	
	public void addData() {
		Vertex a = graph.addVertex(null);
		Vertex b = graph.addVertex(null);
		a.setProperty("name","John");
		b.setProperty("name","Jane");
		
		Edge e = graph.addEdge(null, a, b, "knows");
		e.setProperty("since", 2006);
		
		graph.commit();
	}
	
	public void closeGraph() {
		if(!isGraphOpen) {
			System.out.println("Graph is already closed.");
			return;
		}
		graph.shutdown();
		isGraphOpen = false;
	}

	public static void main(String[] args) {
		Titan titan = new Titan();
		titan.openGraph();
		
		int count = 0;
		for(Vertex vertex: titan.graph.getVertices()) {
			System.out.println(vertex.getProperty("name"));
			count++;
		}
		
		if(count == 0) {
			System.out.println("The graph is empty.");
			System.out.println("Adding some data..");
			titan.addData();
			System.out.println("Data added. Run again to see changes.");
		}
		
		titan.closeGraph();
	}
}

Hope you found this helpful. That’s all folks!