Pouring Coffee into the Matrix Building Java applications on Neo4j Jennifer Reif [email protected] @JMHReif github.com/JMHReif jmhreif.com linkedin.com/in/jmhreif

Who is Jennifer Reif? Developer Advocate, Neo4j • Continuous learner • Conference speaker • Tech blogger • Other: geek Jennifer Reif [email protected] @JMHReif github.com/JMHReif jmhreif.com linkedin.com/in/jmhreif

What is graph?

What is graph? • Database - data storage • Way to store relationships with entities • Powerful when… • Queried - results based on the network structure • Visualized - depth comprehension of network • Utilized in algorithms/pipelines - factoring network into calculations

Graph history • Much older than technology… • Arose from solution need (then and now) Seven Bridges of Konigsberg problem. Leonhard Euler, 1735

Graph Data Model

Property graph • Node (vertex) • Relationship (edge)

Nodes • Represent objects or entities • Can be labeled Category Feature JavaVersion

Nodes • Represent objects or entities • Can be labeled • May have properties Category Feature JavaVersion version: “17” gaDate: 2021-09-14 name: “lang” title: “Pattern Matching for switch”

Relationships • Must have a type • Must have a direction (stored) • Can be read in either direction Category Feature JavaVersion version: “17” gaDate: 2021-09-14 INCLUDES BELONGS_TO name: “lang” title: “Pattern Matching for switch”

Relationships • Must have a type • Must have a direction (stored) • Can be read in either direction • May have properties Category Feature JavaVersion version: “17” gaDate: 2021-09-14 INCLUDES BELONGS_TO featureCount: 3 CHANGES name: “lang” title: “Pattern Matching for switch”

Relationships • Must have a type • Must have a direction (stored) • Can be read in either direction • May have properties • Nodes can have multiple relationships Category Feature JavaVersion version: “17” gaDate: 2021-09-14 INCLUDES BELONGS_TO featureCount: 3 CHANGES STARTED_IN name: “lang” title: “Pattern Matching for switch” IM PACTED_BY

Label • Group of nodes • Like a category • Domain class :) Person

Label • Group of nodes • Like a category • Domain class :) • Inheritance :) Person Employee Customer

Properties • Key-value pair • Associated with node or relationship • Like a variable name and value Category JavaVersion version: “17” CHANGES gaDate: 2021-09-14 featureCount: 3 version: “6” codeName: “Mustang”

Modeling

Whiteboard friendliness

Graph data

Java dev: why graph?

Answering data questions • Java versions (i.e. 8, 11, 17) • Changes between versions over time • Di ff s • History for one speci fi c feature

Domain/Application alignment • Class • Entity/Object • Represents domain type • Variables/Properties • Details for that entity • Constructor - instance of object • Each instance is unique object with varying info @Node public class JavaVersion { @Id @Property("version") private fi nal String javaVersion; private String name, codeName, status, apiSpec; private LocalDate gaDate, eolDate; }

Retaining relationships • Adding relationships • Add variable as pointer to another object • Links entities together • Might have some annotations for mapping @Node public class JavaVersion { @Relationship(“FROM_NEWER”) private List olderVersionDiffs; }

Prep for code!

Neo4j - cloud AuraDB • Free tier • Java language version data loaded

Language drivers • Neo4j Java driver (o ffi cial) • Spring Data Neo4j (SDN) • Includes Java driver dependency • Other options: • O ffi cial drivers -> Python, JavaScript, Go, .NET • Java frameworks -> Quarkus, Helidon, Micronaut, etc

Spring provisions • Spring Initializr • SB reduce boilerplate • Annotation-based OGM for POJOs • Query derivation + DSL for custom (Cypher) • Spring Data easy-connect to Neo4j

Let’s code!

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Resources • Code: github.com/JMHReif/pouring-co ff ee-into-matrix • Spring Data Neo4j docs: dev.neo4j.com/sdn-docs • Neo4j AuraDB: dev.neo4j.com/aura-java • NODES: dev.neo4j.com/nodes24 Jennifer Reif [email protected] @JMHReif github.com/JMHReif jmhreif.com linkedin.com/in/jmhreif