https://github.com/fillmore-labs/value-comparison

Comparison of value objects in Java
https://github.com/fillmore-labs/value-comparison

autovalue bazel builder-pattern code-generation domain-driven-design freebuilder immutables java java-records java17 lombok scala value-object value-semantics

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Comparison of value objects in Java

• Host: GitHub
• URL: https://github.com/fillmore-labs/value-comparison
• Owner: fillmore-labs
• License: apache-2.0
• Created: 2021-10-26T20:47:47.000Z (over 4 years ago)
• Default Branch: main
• Last Pushed: 2026-01-30T00:44:18.000Z (14 days ago)
• Last Synced: 2026-01-30T14:41:53.685Z (14 days ago)
• Topics: autovalue, bazel, builder-pattern, code-generation, domain-driven-design, freebuilder, immutables, java, java-records, java17, lombok, scala, value-object, value-semantics
• Language: Java
• Homepage:
• Size: 458 KB
• Stars: 2
• Watchers: 1
• Forks: 0
• Open Issues: 10
• Metadata Files:
  • Readme: README.adoc
  • Changelog: CHANGELOG.adoc
  • License: LICENSE

Awesome Lists containing this project

README

          
= Value Objects in Java

:Author:    Oliver Eikemeier

:Email:     

:Date:      2021-12

:Revision:  v0.1.1

:toc: macro

ifdef::env-github[]

:note-caption: :information_source:

:tip-caption: :bulb:

endif::[]

image:https://badge.buildkite.com/13a9640ff1e11890cfcfc26bde3dcc40ffd6617f062e67a35e.svg?branch=main[title="Buildkite build status",link=https://buildkite.com/fillmore-labs/value-objects-in-java]

image:https://codecov.io/gh/fillmore-labs/value-comparison/branch/main/graph/badge.svg?token=4KRPCM9FRT[title="Codecov test coverage",link=https://codecov.io/gh/fillmore-labs/value-comparison]

image:https://api.codeclimate.com/v1/badges/d2d37684cb129ef18713/maintainability[title="Code Climate maintainability",link=https://codeclimate.com/github/fillmore-labs/value-comparison/maintainability]

Demo code about value objects and how to create them in Java.

toc::[]

== Purpose

This source demonstrates how to create value objects in Java using various annotation processors.

== Evaluated Libraries

- https://github.com/google/auto/blob/main/value/userguide/index.md[AutoValue]

- https://freebuilder.inferred.org[FreeBuilder]

- https://immutables.github.io[Immutables]

- https://projectlombok.org[Project Lombok]

Also, simple https://docs.oracle.com/en/java/javase/17/language/records.html[record classes],

https://docs.scala-lang.org/tour/case-classes.html[Scala case class] amd

https://kotlinlang.org/docs/data-classes.html[Kotlin data class] examples are included for

demonstration purposes.

== Structure

In `+com.fillmore_labs.talk.value.simple.*+` we have simple classes, one `+EmailAddress+` which

demonstrates the power of being able to check value objects for consistency during construction and

`+Person+`, which show how different libraries handle optional parameters and documentation

propagation.

`+com.fillmore_labs.talk.value.inheritance.*+` and `+com.fillmore_labs.talk.value.composition.*+` demonstrates

the https://en.wikipedia.org/wiki/Composition_over_inheritance[composition over inheritance]

principle and why value objects can not meaningfully extend each other.

== Running

=== Prerequisites

You need https://github.com/bazelbuild/bazelisk[Bazelisk] installed, see also

https://docs.bazel.build/versions/main/install-bazelisk.html[Installing Bazel using Bazelisk].

==== macOS

Using https://brew.sh[HomeBrew] enter

[source,shell]

brew install bazelisk

==== Windows

Using https://chocolatey.org[Chocolatey] enter

[source,shell]

choco install bazelisk

Enable developer mode:

. Open Windows settings

. Go to “Update & security”, then “For developers”

. Under “Developer Mode” section enable “Install apps from any source, including loose files”.

or run with administrator privileges.

=== Main App

The main app simply demonstrates the `toString()` method with a simple structure.

Run it with

[source,shell]

----

bazelisk run //:value-comparison

----

=== Tests

To run all tests, use

[source,shell]

----

bazelisk test //src/test/...

----

[bibliography]

== References

* Joshua Bloch.

https://www.pearson.com/us/higher-education/program/Bloch-Effective-Java-3rd-Edition/PGM1763855.html[Effective Java, 3rd Edition].

Addison-Wesley Professional. 2018.

* Martin Odersky, Lex Spoon, Bill Venners. https://www.artima.com/lejava/articles/equality.html[How to Write an Equality Method in Java]. 2009

* Dan Bergh Johnsson.

https://www.infoq.com/presentations/Value-Objects-Dan-Bergh-Johnsson/[Power of Value - Power Use of

Value Objects in Domain Driven Design]. QCon London. 2009.

* Brian Goetz. https://cr.openjdk.java.net/~briangoetz/amber/datum.html[Data Classes and Sealed Types for Java]. 2019.

* JEP 395. https://openjdk.java.net/jeps/395[Records]. 2020.