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Introduction

In this practical, you will take the microservice from Practical 1 and change it to use a database with Micronaut Data.

What you should already know

You should be able to:

  • Implement basic Micronaut microservices that respond to HTTP requests (from Practical 1).

You should be familiar with these concepts from the lectures:

  • The distinction between compute-intensive and data-intensive systems.
  • The challenges related to the object/relational impedance mismatch.
  • The differences between JDBC database drivers, ORM libraries, and Micronaut Data itself.
  • The JPA annotations for persistent fields, one-to-many, many-to-one, and many-to-many relationships.
  • The conventions followed by the methods in Micronaut Data @Repository interfaces.
  • The use of @Transactional to wrap invocations of controller methods in transactions.

What you will learn

  • How to add Micronaut Data and Micronaut Flyway to an existing project.
  • How to map a database schema to JPA annotations.
  • How to query and update a database via Micronaut Data repositories.
  • How to integrate the database into the tests of Micronaut microservices.

What you will need

  • Java 17 or newer: install from Adoptium.
  • An IDE with Gradle and Java support: in this worksheet, we discuss IntelliJ IDEA.
  • A local installation of Docker Desktop. Ensure Docker Desktop is running before you start this practical.
    • Note: if using a lab machine, you will need to boot Windows as Docker Desktop is not installed in the Linux image.

If you have a recent installation of Docker Desktop (using Docker Engine 29 or newer), you will need to tell the Docker Java libraries to use version 1.44 of the Docker API, until this issue in Micronaut is fixed. From a Linux/Mac terminal, or from Git Bash in Windows, run this command:

echo api.version=1.44 > $HOME/.docker-java.properties

If you do not have Git Bash on Windows, you can run this from PowerShell instead:

"api.version=1.44" | set-content $HOME/.docker-java.properties -Encoding Ascii

What you will do

You will extend a solution of Practical 1 to use a database for persisting its data. This may be your own solution, or the model solution in the VLE.