Neo4j Training Series - Spring Data Neo4j

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Spring Data Neo4j
Concepts & Application Development
Gerrit Meier and Michael Simons,
SDN and OGM team @ Neo4j

Who are we?
Michael Simons Gerrit Meier

Who are you?
• Java Developer
• Graph Specialist
• Where are you from?
• …

Today’s plan
• Get your development environment set up (If not already done)
• Create Neo4j Java Driver-based Spring Boot applications
• Concepts and Architecture of Spring Data Neo4j
• Advance to a Spring Data Neo4j application
◦ Modelling
◦ Repositories
• Control what gets loaded
• Custom queries and projections
• Working with Neo4jTemplate
• Use Neo4jTemplate features
• Testing
• Add tests to your application

Development environment
• (free) Aura instance running
• JDK 17
◦ Driver and Spring Boot
• IDE
• Allow access to download artifacts from Maven Central
• Docker for testing

Database preparation

Spring Boot application
• start.spring.io
• no dependencies
• Maven/Gradle choose
◦ Choose what you are comfortable with
◦ Will use Maven

8
Live coding / code along
Project setup

9
Practical part
Create a Spring Boot application
using the Neo4j Java Driver.
Todo:
• Add Neo4j Java
Driver
• Configuration in
application.properties
• Implement
CommandLineRunner
• Output all Movie-node
titles

Spring Data Neo4j Architecture
Neo4j Java Driver spring-boot-autoconfigure
provides

Neo4j Java Driver
spring-boot-starter-data-neo4j
spring-boot-autoconfigure
provides
provides
Spring Data Neo4j

Spring Data Repositories
Neo4j Template
Neo4j Client
Neo4j Java Driver
spring-boot-starter-data-neo4j
spring-boot-autoconfigure
provides
provides

@Node("Person")
public class Actor {
@Id
public final String name;
@Relationship("ACTED_IN")
public final List<Movie> movies;
public Actor(String name, List<Movie> movies) {
this.name = name;
this.movies = movies;
}
}
@Node
public class Movie {
@Id
public final String title;
public Movie(String title) {
this.title = title;
}
}

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Spring Data Neo4j (starter) dependency
Model domain classes
First repository

16
Practical part
Enrich the application by a
PersonRepository with additional
functionality.
Todo:
• Create a repository
for the Person
• Return Tom Hanks
with all Movies, he
acted in.

@Node
public class Person {
@Id
public final String name;
public Person(String name) {
this.name = name;
this.movies = movies;
}
}
@Node
public class Movie {
@Id
public final String title;
@Relationship(type="ACTED_IN", direction=
Relationship.Direction.INCOMING)
public List<Person> actors;
@Relationship(type="DIRECTED", direction=
public List<Person> directors;
@Relationship(type="PRODUCED", direction=
public List<Person> producers;
public Movie(String title) {
this.title = title;
}
}

More on repositories
Custom queries
• Form your fetch shape by hand

More on repositories
Projections
• Let SDN form your fetch shape

20
Practical part
Use existing functionality in
Spring Data Neo4j to load only the
data you are interested in.
Todo:
• Custom query:
Find a Movie by title
with just the actors
attached
• Projection:
Find a Movie by title
with just the actors
(additional
PersonProjection)

Pitfalls of Sub-Graph loading
• Loaded slice is incomplete
◦ SDN takes the object (graph) to persist as the only truth
◦ Relationships will get removed
• Open projections (DTOs) will adapt entity metadata and fall back to
original query creation
◦ Also in multi-level projections starting with interfaces
• Use-case specific projections
◦ A lot of interfaces/classes for each use-case

22
Neo4jTemplate with Projections

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Practical part
Use projections for save
operations.
Todo:
• Load Movie via
Neo4jTemplate the
Movie -> Actor
projection
• Edit the Movie
(release year) and call
save
• Ensure that all
relationships still exist

Testing
• Testslice @DataNeo4jTest
◦ Set up transaction manager, repositories, etc.
• Testcontainers Neo4j
◦ Docker based solution to run integration tests

25
Practical part
Use projections for save
operations.
Todo:
• Load Movie via
Neo4jTemplate the
Movie -> Actor
projection
• Edit the Movie
(release year) and call
save
• Ensure that all
relationships still exist

..there is more, but just so little time
• Reactive support
• More query styles, like find by example
• Fluent Neo4jClient API
• …

Stay connected
• GitHub project pages
◦ https://github.com/spring-projects/spring-data-neo4j
• Neo4j Community
◦ https://community.neo4j.com/c/drivers-stacks/spring-data-neo4j-ogm/30
• Developer Blog
◦ https://medium.com/neo4j

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Thank you!

Neo4j Training Series - Spring Data Neo4j

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