Cliff Notes: What Java Developers Need to Know About Graph Databases

Cliff Notes:
What Java Developers Need to Know

About Graph Databases
Jennifer Reif

Email: [email protected]

Twitter: @JMHReif

Website: jmhreif.com

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Who Am I? - Jennifer
• Developer + Advocate

• Continuous learner

• Conference speaker

• Blogger

• Geek
Jennifer Reif


Twitter: @JMHReif


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It’s all about data
• Applications are built on data

• Ever had project where only features explained, not data?

• How did it go?

• Was product off of expectations?

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Alternative: Domain-Driven Design (DDD)
• Mutual understanding of domain, concepts

• Iterations

• Understanding data = better understanding of result

• Better product, minimum functionality

• Sanity check code

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Simple or grand foundation?

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Data storage

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Databases
• Database: a structured set of data held in a computer, especially one that is
accessible in various ways

• Relational? NoSQL? Other?

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Relational Database (RDBMS)
• Oracle: 1979

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Relational Database
• No data model limitations

• Memory-efficient for both read and write

• CPU-intensive

• Difficult query language

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Document Database
• MongoDB: 2007
"customer" : {
"id": "123",
"firstName" : "Jane",
"lastName" : "Doe",
"DOB" : "03/12/1989",
"department" : "Engineering",
"phoneNumbers" : {
{
"type" : "office",
"number" : "650-123-4567"
}
{
"type" : "cell",
"number" : "650-321-7654"
}
}
"title" : "Director of QA"
}

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Document Database
• Easy to query (No SQL)

• Easy horizontal scalability

• Little flexibility (relationships pre-baked in document)
"customer" : {
"id": "123",
"firstName" : "Jane",
"lastName" : "Doe",
"DOB" : "03/12/1989",
"department" : "Engineering",
"phoneNumbers" : {
{
"type" : "office",
"number" : "650-123-4567"
}
{
"type" : "cell",
"number" : "650-321-7654"
}
}
"title" : "Director of QA"
}

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Graph Database
• Neo4j: 2007

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Graph Database
• No CPU vs Memory/Storage tradeoff (as in relational dbs)

• No benefit in non-relational data sets

• Still a query language

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Have to pick just one?
• Polyglot persistence: using multiple persistence strategies, each serving a
different need

• “Using the right tool for the job”

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Java Application Data Store Options
• Relational

• Straight JDBC

• JDBC Template

• JOOQ

• JPA or Hibernate

• NoSQL - Document

• MongoDB

• Graph

• Neo4j

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What is a graph?

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What is a graph?
• Much older than tech of the last decade…

• Arose from solution need (then and now)
Seven Bridges of Konigsberg problem. Leonhard Euler, 1735

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Java domain
• Find field changes between Java 17 and Java 8?

• Update doc URL for a Class

• Find most similar diffs (which affected same components)

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Enter stage right - graphs
• Document path (not just data)

• Answering how and why

• Understanding connections

• Find alternates, impacts, etc

• Produce better assumptions, decisions

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Neo4j

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Extremes in Development

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Stability
• ACID compliance

• Relationships at write vs read

• Scaling (vertical+horizontal)

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Innovation
• Cypher vs SQL

• Schema-less vs schema-enforced

• Graph modeling vs ERD

• Integrations

• Cloud/on-premises solutions

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Java dev:

Why Graph?

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Java domain
• Java Versions (i.e. 8, 11, 17)

• Changes between versions over time

• Diffs

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Java Entity - Domain Class
• Class

• Entity/Object

• Represents domain type

• General outline for objects of that type

• Variables/properties

• Details for that entity

• Values may not always exist

• Constructor - instance of object

• Each instance is unique object with varying info

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Demo: Let’s create one

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Java Domain Relationships
• Adding relationships

• Add variable as pointer to another object

• Links entities together

• Might have some annotations for mapping

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Demo: Let’s add that

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Graph Data Model

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Property Graph
• Node (vertex)

• Relationship (edge)

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Nodes
• Represent objects or entities

• Can be labeled
JavaVersion VersionDiff

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Nodes
• Represent objects or entities

• Can be labeled

• May have properties JavaVersion VersionDiff
version: “17”

gaDate: 2021-09-14
fromVersion: “17.0.3+7-tem”

toVersion: “1.6.0_45-oracle”
JavaVersion
version: “6”

gaDate: 2006-12-12

codeName: “Mustang”

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Relationships
• Must have a type

• Must have a direction
FROM_NEWER
version: “17”

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Relationships


• May have properties
M
IG
RATES
versionSteps:
3
FROM_NEWER
version: “17”

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Relationships


• May have properties

• Nodes can share multiple
relationships
M
IG
RATES
versionSteps:
3
FROM_NEWER
version: “17”

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Label
• A group of nodes

• Like a category

• Domain class :)
Person

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Label
• A group of nodes

• Like a category

• Domain class :)
Person
Employee
Customer

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Property
• Key-value pair

• Associated with node or relationship

• Like a variable name and value
M
IG
RATES
versionSteps: 3
JavaVersion
version: “17”
JavaVersion
version: “6”
gaDate: 2021-09-14
gaDate: 2006-12-12
codeName: “Mustang”

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Demo model

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Whiteboard-friendliness

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JDK Full Data Model

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JDK Data Model

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Java devs: Why Choose Graphs?
• Data model match - application to database

• Less data model mapping = more efficient application coding

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Other types of graphs?
• Resource Description Framework (RDF)

• Triples: subject (node), predicate (rel), object (node)

• Often web-based data

• Often XML format

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Query in a Graph vs
Relational DB

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SQL vs Cypher
SELECT j.JavaVersion, j.Status, j.GaDate, j.EolDate,

d.fromVendor, d.fromVersion, d.toVendor, d.toVersion

FROM JavaVersion j

LEFT JOIN DiffList dl ON dl.JavaVersion = j.JavaVersion

LEFT JOIN VersionDiff d ON dl.FromVersion = d.FromVersion;
MATCH (j:JavaVersion)-[r:FROM_NEWER]->(d:VersionDiff)

RETURN j, r, d;
SQL
Cypher
DiffList

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Cypher
• Functional and visual

• Based on ASCII-art

• Declarative query language

• Focuses on what to retrieve

• Not how
A B
LIKES
MATCH ( A ) - [ : LIKES] - > ( B )

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Cypher: powerful and expressive
Jennifer Neo4j
WORKS_FOR
CREATE (:Person { name: ‘Jennifer’}) -[:WORKS_FOR]-> (:Company { name: ‘Neo4j’})
NODE
PROPERTY
NODE
PROPERTY
LABEL LABEL

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Cypher: read
Jennifer Neo4j
WORKS_FOR
MATCH (:Person { name: ‘Jennifer’} ) -[:WORKS_FOR]-> ( whom )
 
RETURN whom

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Let’s Query!

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Java Ecosystem
• Language drivers

• Framework support

• Spring, Quarkus, Micronaut, etc

• Connectors

• APOC, Neosemantics, ETL, Spark, etc

• Visualization tools

• Import/export

• Database integrations

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Let’s code!

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Keep in mind…
• Relational

• JPA or Hibernate

■ Mismatch between models

■ Set theory and relational algebra

• Graph

• Neo4j

■ More object-oriented model

■ Based on graph theory and network theory

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Resources
• Code: github.com/JMHReif/pouring-coffee-into-matrix-lombok

• Neo4j AuraDB: bit.ly/neo4j-aura

• Blog: bit.ly/jmhreif-blog
Jennifer Reif


Twitter: @JMHReif


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Cliff Notes: What Java Developers Need to Know About Graph Databases

Cliff Notes: What Java Developers Need to Know About Graph Databases

Jennifer Reif

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