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https://github.com/eventsourcing/es4j

Event capture and querying framework for Java
https://github.com/eventsourcing/es4j

database event-sourcing java

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Event capture and querying framework for Java

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README 

        
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# ![logo](https://eventsourcing.com/android-icon-48x48.png) Eventsourcing for Java



### *Enabling plurality and evolution of domain models*



Instead of mutating data in a database, Eventsourcing stores all changes (*events*) and what caused them (*commands*). To make this data useful,

Eventsourcing builds indices over it.



This helps developing applications faster because there is no need to worry

about designing the *right* domain models upfront (or as close to *right* as possible). By keeping all the commands and events, we can enrich or change

our domain models over time with very little friction. Furthermore, this approach removes a need to have a *one and only* domain model for every entity. We experience the world and reality in different ways, depending on circumstances and points of view, and our programs should be able to reflect that.



To learn more about what kind of problems ES4J addresses, please read [Why Use Eventsourcing Database](https://blog.eventsourcing.com/why-use-eventsourcing-database-6b5e2ac61848)



[![Lazy event sourcing: living in the now](https://www.dropbox.com/s/k2zdv7ez9wq4zog/lazy_eventsourcing_video.png?dl=1)](https://www.youtube.com/watch?v=aqv8d1pjmU8)



## Key benefits



* Domain model flexibility

* Late domain model binding

* Persistence of causal information

* Serializable conflict resolution

* Audit trail logging

* Mapping application functionality



## Key features



* Strongly typed schemas

* Event migrations

* Domain protocols

* Batteries included (shared event languages)

* Basic support for [Kotlin](http://kotlinlang.org)

* Causality-preserving [Hybrid Logical Clocks](http://www.cse.buffalo.edu/tech-reports/2014-04.pdf)

* In-memory and server (**PostgreSQL**) storage

* Locking synchronization primitive

* JMX-based introspection and management



# Presentation



You can find our current slide deck at https://eventsourcing.com/presentation



# Downloading and installing



To start using ES4J, please follow the [installation instructions](https://es4j.eventsourcing.com/docs/master/getting_started/install.html).



# Documentation



Documentation can be found at [es4j.eventsourcing.com](https://es4j.eventsourcing.com/docs/master)



We strive to specify the building blocks behind Eventsourcing and its ecosystem as succinct specifications, you can find the current list of them at [rfc.eventsourcing.com](http://rfc.eventsourcing.com)



# Roadmap



As this project is striving to be a decentralized, contributors-driven project governed by the [C4 process](http://rfc.unprotocols.org/spec:1/C4), there is no central roadmap per se. However, there's a [centralized list of reported issues](https://github.com/eventsourcing/es4j/issues). These do not imply an actual roadmap, just what has been reported, ranging from bugs to longer-term  design issues.



# Contributing



Contributions of all kinds (code, documentation, testing, artwork, etc.) are highly encouraged. Please open a GitHub issue if you want to suggest an idea or ask a question.



We use Unprotocols [C4 process](http://rfc.unprotocols.org/1/). In a nutshell, this means:



* We merge pull requests rapidly (try!)

* We are open to diverse ideas

* We prefer code now over consensus later



For more details, please refer to [CONTRIBUTING](CONTRIBUTING.md)



# Related projects



* [es4j-graphql](https://github.com/eventsourcing/es4j-graphql) A Relay.js/GraphQL adaptor for ES4J-based applications.