Graph Database Support

In a fast connecting and complex world, Graph databases like Neo4j, InfiniteGraph etc are getting popular because they provide lightning-fast access to complex data found in social networks, recommendation engines and networked systems among other similar problems.

Kundera supports Neo4j which is probably the most popular graph database till date. Our journey to making this work has been bumpy because of complex structure of the graph and challenges in fitting things into JPA, specification on which Kundera is based.

If you are new to Kundera, you can start with what is Kundera and Getting started in 5 minutes.

IMDB Example

We'll be using famous IMDB example for our demonstration. Below is graphical representation of data that we would be representing in the form of entities. (Top two circles are Actor nodes while bottom 3 nodes are Movie nodes. They are connected by edges that represent Role relationships)

Definiing Entities

Actor

import java.util.HashMap;
import java.util.Map;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.MapKeyJoinColumn;
import javax.persistence.Table;

import com.impetus.kundera.index.Index;
import com.impetus.kundera.index.IndexCollection;

@Entity
@Table
@IndexCollection(columns = { @Index(name = "name", type = "KEYS") })
public class Actor
{
    @Id
    @Column(name = "ACTOR_ID")
    private int id;

    @Column(name = "ACTOR_NAME")
    private String name;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @MapKeyJoinColumn(name = "ACTS_IN")
    private Map<Role, Movie> movies;
    
    //Costructors, getters/ setters other methods ommitted.
}

Movie

Role