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Connecting to JanusGraph

JanusGraph can be queried from all languages for which a TinkerPop driver exists. Drivers allow sending of Gremlin traversals to a Gremlin Server like the JanusGraph Server. A list of TinkerPop drivers is available on TinkerPop’s homepage.

In addition to drivers, there exist query languages for TinkerPop that make it easier to use Gremlin in different programming languages like Java, Python, or C#. Some of these languages even construct Gremlin traversals from completely different query languages like Cypher or SPARQL. Since JanusGraph implements TinkerPop, all of these languages can be used together with JanusGraph.

Connecting from Java

While it is possible to embed JanusGraph as a library inside a Java application and then directly connect to the backend, this section assumes that the application connects to JanusGraph Server. For information on how to embed JanusGraph, see the JanusGraph Examples projects.

This section only covers how applications can connect to JanusGraph Server. Refer to ??? for an introduction to Gremlin and pointers to further resources.

Getting Started with JanusGraph and Gremlin-Java

To get started with JanusGraph in Java:

  1. Create an application with Maven:

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    mvn archetype:generate -DgroupId=com.mycompany.project
   -DartifactId=gremlin-example
   -DarchetypeArtifactId=maven-archetype-quickstart
   -DinteractiveMode=false

  2. Add dependencies on janusgraph-core and gremlin-driver to the pom.xml file:

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    ...
<dependencies>
  <dependency>
    <groupId>org.janusgraph</groupId>
    <artifactId>janusgraph-core</artifactId>
    <version>$MAVEN{project.version}</version>
  </dependency>
  <dependency>
    <groupId>org.apache.tinkerpop</groupId>
    <artifactId>gremlin-driver</artifactId>
    <version>$MAVEN{tinkerpop.version}</version>
  </dependency>
...
</dependencies>
...

  3. Add two configuration files, conf/remote-graph.properties and conf/remote-objects.yaml:

    conf/remote-graph.properties.

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    gremlin.remote.remoteConnectionClass=org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteConnection
gremlin.remote.driver.clusterFile=conf/remote-objects.yaml
gremlin.remote.driver.sourceName=g

    conf/remote-objects.yaml.

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    hosts: [localhost]
port: 8182
serializer: { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0,
              config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}

  4. Create a GraphTraversalSource which is the basis for all Gremlin traversals:

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    Graph graph = EmptyGraph.instance();
GraphTraversalSource g = graph.traversal().withRemote("conf/remote-graph.properties");
// Reuse 'g' across the application
// and close it on shut-down to close open connections with g.close()

  5. Execute a simple traversal:

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    Object herculesAge = g.V().has("name", "hercules").values("age").next();
System.out.println("Hercules is " + herculesAge + " years old.");

    next() is a terminal step that submits the traversal to the Gremlin Server and returns a single result.

JanusGraph Specific Types and Predicates

JanusGraph specific types and predicates can be used directly from a Java application through the dependency janusgraph-core.

Connecting from Python

Gremlin traversals can be constructed with Gremlin-Python just like in Gremlin-Java or Gremiln-Groovy. Refer to ??? for an introduction to Gremlin and pointers to further resources.

Important

Some Gremlin step and predicate names are reserved words in Python. Those names are simply postfixed with _ in Gremlin-Python, e.g., in() becomes in_(), not() becomes not_(), and so on. The other names affected by this are: all, and, as, from, global, is, list, or, and set.

Getting Started with JanusGraph and Gremlin-Python

To get started with Gremlin-Python:

  1. Install Gremlin-Python:
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pip install gremlinpython==$MAVEN{tinkerpop.version}

  1. Create a text file gremlinexample.py and add the following imports to it:

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    from gremlin_python import statics
from gremlin_python.structure.graph import Graph
from gremlin_python.process.graph_traversal import __
from gremlin_python.driver.driver_remote_connection import DriverRemoteConnection

  2. Create a GraphTraversalSource which is the basis for all Gremlin traversals:

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    graph = Graph()
connection = DriverRemoteConnection('ws://localhost:8182/gremlin', 'g')
// The connection should be closed on shut down to close open connections with connection.close()
g = graph.traversal().withRemote(connection)
// Reuse 'g' across the application

  3. Execute a simple traversal:

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    herculesAge = g.V().has('name', 'hercules').values('age').next()
print('Hercules is {} years old.'.format(herculesAge))

    next() is a terminal step that submits the traversal to the Gremlin Server and returns a single result.

JanusGraph Specific Types and Predicates

JanusGraph contains some types and predicates that are not part of Apache TinkerPop and are therefore also not supported by Gremlin-Python.

Connecting from .NET

Gremlin traversals can be constructed with Gremlin.Net just like in Gremlin-Java or Gremiln-Groovy. Refer to ??? for an introduction to Gremlin and pointers to further resources. The main syntactical difference for Gremlin.Net is that it follows .NET naming conventions, e.g., method names use PascalCase instead of camelCase.

Getting Started with JanusGraph and Gremlin.Net

To get started with Gremlin.Net:

  1. Create a console application:
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dotnet new console -o GremlinExample
  1. Add Gremlin.Net:
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dotnet add package Gremlin.Net -v $MAVEN{tinkerpop.version}

  1. Create a GraphTraversalSource which is the basis for all Gremlin traversals:

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    var graph = new Graph();
var client = new GremlinClient(new GremlinServer("localhost", 8182));
// The client should be disposed on shut down to release resources
// and to close open connections with client.Dispose()
var g = graph.Traversal().WithRemote(new DriverRemoteConnection(client));
// Reuse 'g' across the application

  2. Execute a simple traversal:

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    var herculesAge = g.V().Has("name", "hercules").Values<int>("age").Next();
Console.WriteLine($"Hercules is {herculesAge} years old.");

    The traversal can also be executed asynchronously by using Promise() which is the recommended way as the underlying driver in Gremlin.Net also works asynchronously:

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    var herculesAge = await g.V().Has("name", "hercules").Values<int>("age").Promise(t => t.Next());

JanusGraph Specific Types and Predicates

JanusGraph contains some types and predicates that are not part of Apache TinkerPop and are therefore also not supported by Gremlin.Net.