Extending

neo4jr-social is meant to be a simple service offering basic neo4j persistance and querying capabilities in a language agnostic way. You will likely want to do more advance things like custom traversing of your graph. To support this neo4jr-social auto loads extensions from a predefined location. Using this option allows you to add arbitrary methods to the neo4jr-social service.

How to configure extensions

• By default neo4jr-social will load any jruby (files ending in .rb) files located at:
  

  ~/.neo4jr-social

• You can also specify a different location to load ruby files from by setting the neo4jr_extensions environment variable. i.e.
  

  export neo4jr_extensions=/path/to/your/extensions

• Or for you java people out there, you can set system property neo4jr.extensions

Example Extension

Creating extensions are super easy

• Create a file i.e.
  

  vim ~/.neo4jr-social/test.rb

• Paste the following into test.rb,
  

  
  
  module Neo4jr
  
    class Service < Sinatra::Base
  
      get ‘/my_custom_action/:node_id’ do
  
        Neo4jr::DB.execute do |neo|
  
          node               = neo.getNodeById(params[‘node_id’].to_s)
  
          order               = Neo4jr::Order::BREADTH_FIRST
  
          stop_when      = Neo4jr::StopEvaluator::END_OF_GRAPH
  
          return_when   = Neo4jr::Return.when do |current_node|
  
            true
  
          end        
  
          relationships = Neo4jr::RelationshipType.outgoing(:acted_in)
  
          traverser = node.traverse(order, stop_when, return_when, relationships)
  
          traverser.map.to_json
  
        end
  
      end
  
    end
  
  end
  
  

• Restart the service
• Test the new GET request /my_custom_action/123