Overview

This project re-implements eventsourcing-example based on the Eligosource Eventsourced library. Regarding library usage, it demonstrates how to

• implement command-sourcing (for managing state of invoices)
• implement event-sourcing (for managing state of payment processes and for recording usage statistics)
• implement domain services (to handle requests via UI and XML/JSON API)
• implement business processes (to deal with long-running background activities)
• recover from crashes (incl. recovery of business processes)

Compared to the old implementation, the whole service and persistence layer are re-written and domain events are now decoupled from the immutable domain model. The web UI and XML/JSON API remain unchanged and are built on top of Jersey, Scalate and JAXB. A Play-based version will follow (which supports asynchronous responses in contrast to Jersey).

Architecture

State management

• Command and event-sourced processors manage state via STM references.
• For reading current state, services access STM references directly (concurrent reads).
• For updating current state, services access STM references via processors (actors) where a single STM reference is updated by a single processor (single-writer-principle).

Build

First checkout, build and publish the Eventsourced library to Ivy cache.

git clone git://github.com/eligosource/eventsourced.git
cd eventsourced
sbt publish-local

Then checkout the example application and compile it

git clone git://github.com/eligosource/eventsourced-example.git
cd eventsourced-example
sbt compile

Run

To start the example application enter

sbt 'run-nobootcp org.eligosource.eventsourced.example.server.Webserver'

Finally go to http://localhost:8080 and create some invoices.

Web API

The example application's RESTful service interface supports HTML, XML and JSON as representation formats. Content negotiation is done via the Accept HTTP header. The following examples show how to get different representations of invoice-3

HTML

Enter http://localhost:8080/invoice/invoice-3 into your browser. Provided you have created an invoice with id invoice-3 before you should see something like

XML

curl -H "Accept: application/xml" http://localhost:8080/invoice/invoice-3

yields

<draft-invoice id="invoice-3" version="2">
    <total>12.8</total>
    <sum>12.8</sum>
    <discount>0</discount>
    <items>
        <item>
            <description>item-1</description>
            <count>1</count>
            <amount>4.1</amount>
        </item>
        <item>
            <description>item-2</description>
            <count>3</count>
            <amount>2.9</amount>
        </item>
    </items>
</draft-invoice>