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The Example Application

Paul Kelly

The example is a Spring Boot REST application called toybank, which has a connection to a database. It has two endpoints for adding or retrieving records. It has unit tests, which use an in-memory database (H2), and end-to-end tests, which require an external database. The end-to-end tests run against a deployed toybank. The application has been kept as simple as possible, as its purpose is to show a separation between the unit and end-to-end tests rather than how to write application code.

Fork the repository here, and then clone it to your local machine. To run the unit tests and build a jar file:

./mvnw package 

or on Windows:

mvnw package  

You should see three tests run with no failures, followed by the Maven “Build Success” message.

Set up local database

The application uses a PostgreSQL database that you can run inside a container. Here’s a Docker Compose file for running PostgreSQL and pgAdmin containers with persistent volumes stored on the host machine:

version: '2'
      - '5432:5432'
      - 'postgresql_data:/bitnami/postgresql'
    - postgresql_net
      - POSTGRESQL_USERNAME=postgres
      - POSTGRESQL_PASSWORD=your-db-password
    - '8880:80'
    - postgresql_net
      - PGADMIN_DEFAULT_EMAIL=your-email
      - PGADMIN_DEFAULT_PASSWORD=your-admin-password
    driver: local

To run the database and admin containers:

  1. Create a docker-compose.yml file with the contents above. Edit the values your-db-password, your-email, and your-admin-password to set credentials for your database and for the admin application. The value ofyour-email is only used as the login user for the Postgres admin application.

  2. Run the following command from the directory with docker-compose.yml:

docker-compose up -d
  1. Run the docker ps command afterwards. There should now be two new containers running. You should see output similar to this (IDs will be different and you might have other containers running as well as the two you just started):
CONTAINER ID   IMAGE                   COMMAND                  CREATED          STATUS         PORTS                           NAMES
49cde7079787   dpage/pgadmin4          "/"         11 seconds ago   Up 8 seconds   443/tcp,>80/tcp   postgres_pgadmin_1
60906366563e   bitnami/postgresql:11   "/opt/bitnami/script…"   11 seconds ago   Up 8 seconds>5432/tcp          postgres_postgresql_1\

This file also creates a Docker bridge network for the two containers to communicate with each other. pgAdmin is available on the host at port 8880, so to administer the database, point your browser at http://localhost:8880 and sign in using your-email and your-admin-password. Then, create a new server connection as follows:

  1. Click Add new server under Quick Links.

  2. Set name to postgres-db, then go to the connection tab and enter the name of the PostgreSQL container. It is probably postgres_postgresql_1, but you can check the names of running containers with the docker ps command.

  3. Set Username to postgres and Password to your-db-password and Save the server connection.

You can now administer the database server. Create databases test, and production (the dev database was created by the docker-compose command). To create a new database:

  1. Right-click on Databases under postgres-db, then click Create, Database to add a new database.

Run the application

You can run the application on your host machine before deploying it to a Kubernetes cluster. Set the following environment variables (the value for DATABASE_PASSWORD must be the same as the one for POSTGRESQL_PASSWORD in your docker-compose.yml file):


Then, provided you built the application as described above:

java -jar target/toy-bank-1.0.1.jar

Point your browser at http://localhost:8080 to see a 404 error page (the application doesn’t have a mapping setup for /). You can put a record into the database, however, by making a POST request to http://localhost:8080/transaction/ with the request body set to:

    "accountId" : 2,
    "description" : "Crisps",
    "amount" : 1.25,
    "date" : "2021-12-22"

The response body will look like the following:

    "id": 1,
    "accountId": 2,
    "description": "Crisps",
    "amount": 1.25,
    "date": "2021-12-22"

You can view the record either using the pgAdmin tool, or by pointing your browser at http://localhost:8080/transaction/1. To use the pgAdmin tool, in the right hand pane under Servers, click Refresh then expand postgres-db, Databases, Schemas, Tables, then right-click account_transaction and select View/Edit Data, All Rows.