Sample code

This repo contains sample code to help you get started. Please bear in mind that it is provided for illustrative purposes only, and as such may not be production quality and/or may not fit your use-cases. You may use the contents of this repo in parts or in whole according to the BSD0 license:

Copyright © 2022 Digital Asset (Switzerland) GmbH and/or its affiliates

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Quickstart - Custom Views

This project contains an example using the custom views library to project ledger events to a PostgreSQL table. If you are not familiar with IOUs, please read the IOU overview.

The example provides a script in ProjectionRunner.java to start the projection. It also provides a spring-boot application with a REST API over the projected events in the database.

Note: Before starting, please ensure you have the Daml SDK installed. You can find instructions on how to do that here

Prerequisite

• Maven (https://maven.apache.org/install.html)

• PostgreSql Client

  • MacOS with Homebrew (https://formulae.brew.sh/formula/libpq)

  • Windows (https://www.postgresql.org/download/windows/)

• Docker (https://docs.docker.com/get-docker/)

How to run

In the project directory, compile Daml model with:

daml build

Startup a sandbox ledger in a separate terminal with:

daml sandbox --dar .daml/dist/quickstart-0.0.1.dar

Generate java code from the daml source with:

daml codegen java

Start Navigator with:

daml navigator server

Start a PostgreSQL database with docker compose:

docker-compose up -d db

Create a new database named ious in the Postgres db.

psql -h localhost -p 5432 -U postgres -c 'create database ious'

Initialise ledger with some parties with the following command:

daml script --dar .daml/dist/quickstart-0.0.1.dar --script-name Main:initialize --ledger-host localhost --ledger-port 6865 --static-time

This will print something like the following:

[DA.Internal.Prelude:556]: 'Alice::1220c7b4b153d8dec59ceb424bb700f2c8032ec48a13195f580c8fb099ff0ea196fc'

Export the party Id, in this case Alice::1220c7b4b153d8dec59ceb424bb700f2c8032ec48a13195f580c8fb099ff0ea196fc:

export PARTY_ID="Alice::1220c7b4b153d8dec59ceb424bb700f2c8032ec48a13195f580c8fb099ff0ea196fc"

Start the REST API with the following command:

mvn spring-boot:run

Start the projection runner with the following command:

mvn exec:java -Dexec.mainClass="com.daml.quickstart.iou.ProjectionRunner" -Dexec.args="$PARTY_ID"

You should be able to see events projected to the database by checking the database directly or using one of the APIs below.

• GET /events
• GET /events/observer/<party>
• GET /events/count