spring data neo4j relationship in entity

Question

Image I have the following entity: Company and Employee, with spring data neo4j annotation:

Company.java

@NodeEntity(label = "Company")
public class Company {
    /**
     * Graph ID
     */
    @GraphId
    private Long id;
    ......
}

Employee.java

@NodeEntity(label = "Employee")
public class Employee {
    /**
     * Graph ID
     */
    @GraphId
    private Long id;
    ......
}

Then there is the relationship entity for these entities:

@RelationshipEntity(type = "EMPLOY")
public class EmployRel {
    /**
     * Graph ID
     */
    @GraphId
    private Long id;
    @StartNode
    private Company company;
    @EndNode
    private Employee employee;
    ......
}

So how to keep the reference in Company and Person?

Company.java

@Relationship(type = "EMPLOY", direction = Relationship.OUTGOING)
private Set<EmployRel> employeeRel = new HashSet<>();

OR

@Relationship(type = "EMPLOY", direction = Relationship.OUTGOING)
private Set<Employee> employee = new HashSet<>();

Person.java

@Relationship(type = "EMPLOY", direction = Relationship.INCOMING)
private Company company = new Company();

OR

@Relationship(type = "EMPLOY", direction = Relationship.OUTGOING)
private EmployRel employRel = new EmployRel();

nmervaillie · Accepted Answer · 2017-10-09 16:06:00Z

1

You have to declare in Company (outgoing relationship to Employee through EmployeeRel)

@Relationship
public Set<EmployRel> employees = new HashSet<>();

And the inverse in Employee :

@Relationship(direction = Relationship.INCOMING)
public HashSet<EmployRel> isEmployedBy = new HashSet<>();

Note that here you chose to have the relationship navigable on both sides, but it is not mandatory. It will also work to have it navigable only from Company or Employee.

answered Oct 9, 2017 at 16:06

nmervaillie

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4 Comments

Liping Huang Over a year ago

So how about using UNDIRECTED in the direction?

nmervaillie Over a year ago

UNDIRECTED is a matter of semantics. Let's say you have a PARTNER relationship : you don't really matter the direction, so you can use UNDIRECTED in that case. It will work the same as a directed relationship.

Liping Huang Over a year ago

Thanks, I know this direction semantics, for my case, maybe you need to read my another question indeed, please see - stackoverflow.com/questions/46503104/…, in this question, the company can be the "Investor" and "Investee", so will have the Company -[:INVESTMENT]- Company relationship, this is really the boring things to me.

nmervaillie Over a year ago

I posted a comment there

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