gremlin

gremlin-node

Implementation of Gremlin for node.js. Gremlin-node is a javascript wrapper around the Gremlin API. The node-java module provides the bridge between node and Java, allowing gremlin-node to access java classes and methods.

N.B. Gremlin-node is still in development.

Dependancies

node-java

Bridge API to connect with existing Java APIs. Please read the node-java installation notes, as it outlines how to install the node-java module on specific platforms and it's dependancies. N.B. One of it's dependancies is python 2.x.

Installation

$ npm install gremlin

Within the module directory, place the relevant .jar files for the desired Blueprints. You can put them into the lib directory or create a new folder. You can organise them how you please. Gremlin-node will find them. Class files will however, need to be placed in the lib directory.

Then in node:

var g = require(“gremlin”),
    T = g.Tokens;

Introduction

Node.js adopts a non-blocking I/O model, which means function calls are asynchronous. Node-java remains true to this model and requires that calls to Java are also asynchronous and therefore require a callback. See the example below, the add method has a node style callback.

var list = new ArrayList();

list.add("itemA", function(err, result) {
    if(err) { console.error(err); return; }
});

However, node-java does allow for synchronous calls, but requires that the method name be suffixed with the word 'Sync'. The example below shows the add method being called synchronously.

var list = new ArrayList();

list.addSync('item1');

There is no need to add 'Sync' to gremlin-node functions, as they are synchronous by default. Gremlin-node tries to implement Gremlin syntax as closely as possible. However, there are some differences.

• All method calls require brackets (), even if there are no arguments.

• Closures passed in as string.

  g.v(1).out().gather('{it.size()}')
  

• Float's are not native javascript Types so need to be passed in as a string to gremlin-node methods. Floats need to be suffixed with a 'f'.

  g.v(1).outE().has("weight", T.gte, "0.5f").property("weight")
  

As mentioned above, gremlin-node is a javascript wrapper. You are, however, able to access the gremlin pipeline by calling the pipe or iterator methods. These methods return the Java version of the Gremlin pipeline. You need to provide a callback or append 'Sync' to the method names for calls against this object. This will become clearer as we go along.

##Connect to Graph

###TinkerGraph

var TinkerGraphFactory = g.java.import("com.tinkerpop.blueprints.impls.tg.TinkerGraphFactory");
var tg = TinkerGraphFactory.createTinkerGraphSync();
g.SetGraph(tg);

###OrientGraph

var OrientGraph = g.java.import('com.tinkerpop.blueprints.impls.orient.OrientGraph');
var graphDB = new OrientGraph('remote:localhost/tinkerpop', 'admin', 'admin');
g.SetGraph(graphDB);

###Titan

var BaseConfiguration = g.java.import('org.apache.commons.configuration.BaseConfiguration');

conf = new BaseConfiguration();
conf.setPropertySync("storage.backend","cassandra");
conf.setPropertySync("storage.hostname","127.0.0.1");
conf.setPropertySync("storage.keyspace","titan");

var TitanFactory = g.java.import('com.thinkaurelius.titan.core.TitanFactory');
gt = TitanFactory.openSync(conf);
g.SetGraph(gt);

##Working with the Database

Once you have connected to the database, you are able to call all implementation specific database methods.

For example, here is how you would asynchronously add a Vertex, once you have connected to a TinkerGraph as described above.

tg.addVertex(100, function(err, newVertex){
    newVertex.name = 'stephen';
});

And heres how you would add a Vertex synchronously.

var newVertex = tg.addVertexSync(101);
newVertex.name = 'frank';

Examples

A good resource to understand the Gremlin API is GremlinDocs. Below are examples of gremlin and it's equivalent gremlin-node syntax.

Example 1: Basic Transforms

gremlin>  g.V('name', 'marko').out

node>     g.V('name', 'marko').out();

node>     g.V({name: 'marko'}).out();

gremlin>  g.v(1, 4).out('knows', 'created').in

node>     g.v(1, 4).out('knows', 'created').in();

node>     g.v([1, 4]).out(['knows', 'created']).in(); 

Example 2: [i]

gremlin>  g.V[0].name

node>     g.V().index(0).property('name');

Example 3: [i..j]

gremlin>  g.V[0..<2].name

node>     g.V().range(0,1).property('name');

Example 4: has

gremlin>    g.E.has('weight', T.gt, 0.5f).outV.transform{[it.id,it.age]}

node>       g.E().has('weight', T.gt, '0.5f').outV().transform('{[it.id,it.age]}');

Example 5: and & or

gremlin>  g.V.and(_().both("knows"), _().both("created"))

node>     g.V().and(g._().both("knows"), g._().both("created"));

gremlin>  g.v(1).outE.or(_().has('id', T.eq, "9"), _().has('weight', T.lt, 0.6f))

node>     g.v(1).outE().or(g._().has('id', T.eq, 9), g._().has('weight', T.lt, '0.6f')); 

Example 6: groupBy

gremlin>    g.V.out.groupBy{it.name}{it.in}{it.unique().findAll{i -> i.age > 30}.name}.cap

node>       g.V().out().groupBy('{it.name}{it.in}{it.unique().findAll{i -> i.age > 30}.name}').cap();

Example 7: retain

gremlin>  g.V.retain([g.v(1), g.v(2), g.v(3)])

node>     g.V().retain([g.v(1), g.v(2), g.v(3)]);

Example 8: groupBy with map

gremlin>    m = [:]

gremlin>    g.V.groupBy(m){it}{it.out}.iterate();null;

node>       var map = new g.HashMap();

node>       g.V().groupBy(map, '{it}{it.out}').iterate();

Example 9: aggregate

gremlin>    x = []

gremlin>    g.v(1).out.aggregate(x).out.retain(x)

node>       var x = new g.ArrayList();

node>       g.v(1).out().aggregate(x).out().retain(x);

Example 10: accessing returned values

node>       g.v(1).out().iterator().toListSync();

node>       g.v(1).out().toList();

node>       g.v(1).out().toJSON();

Author

Frank Panetta - Follow @entrendipity

##License ###The MIT License (MIT)

Copyright (c) 2013 entrendipity pty ltd

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.