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Introduction

In this practical, you will extend the book-related microservice by adding an integration with the OpenLibrary APIs to fetch more information about the books that are added to the database.

What you should already know

You should be able to:

  • Implement basic Micronaut microservices that respond to HTTP requests (from Practical 1).
  • Query and update a relational database within a Micronaut microservice using Micronaut Data (from Practical 2).

You should be familiar with these concepts from the lectures:

  • The differences between in-process and inter-process communication.
  • How the Gateway pattern helps encapsulate the details of interacting with an external service.
  • The main elements in an OpenAPI specification, and its use for generating clients.

What you will learn

  • How to use the Micronaut OpenAPI Gradle plugin to generate a client from an existing specification.
  • How to develop and test a Gateway for a specific external service (the OpenLibrary API).
  • How to integrate the Gateway for improving the information you have about a book in the background.

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 start from a solution of Practical 2 (either yours, or our model solution) and work through the rest of the sections.