Playground for PACT in context of React, WebSphere Liberty and PostgreSQL

Introduction

This project was developed as a proving ground for the use of WebSphere Liberty for Developers, backed by PostgreSQL, to support a React web application.

In the course of developing the PoC, we implemented some API unit tests using Pact for Consumer-Driven Contract Testing. The advantages seen were that

• the consumer (client, application) can test its data access layer without requiring the back-end to be running
• the API can be tested easily for conformance to the consumer's requirements
• like TDD, using the consumer-driven approach means that the back end will not develop any capabilities or features that are not required by the front end
• there is potential for building all this into the CI/CD pipeline, which prevents deploying any API or client application that is not conformant with the API contract

Prerequisites

The examples all use IntelliJ Idea, but any other IDE should do equally well. After cloning the repository, it is advisable to use IntelliJ's File --> Open menu command to select the folder that encloses the cloned repo.

You need Docker Desktop. Download and install it from https://www.docker.com/products/docker-desktop/ .

Initialising

From a Mac OS or Linux command line, run the script ./init.sh.

Starting and stopping

Start the container by running the script ./start.sh. Note that this will monopolise a terminal. Open another terminal for the next command.

Connect to the container by running ./exec.sh.

Stop the container by running the script ./stop.sh.

When the container is running, you can access the default server like this:

http://localhost:9080/openapi/ui/

See the standard output from the server to check what other endpoints are exposed.

Deploying an application

You can connect to the container and run server management commands such as

/liberty/wlp/bin/server create SERVERNAME

/liberty/wlp/bin/server start SERVERNAME

/liberty/wlp/bin/server stop SERVERNAME

If you add an application (such as helloworld) in this project and build it, e.g. using the Maven package target, you should find that a WAR file has been created under the target directory.

Move it to the folder out/wlp/usr/servers/SERVERNAME/apps by dragging and dropping in the IDE project explorer view.

You'll have to modify the server.xml file appropriately. Most of the necessary settings can be cribbed from the helloworld example.

You will also then have to run further commands inside the container:

/liberty/wlp/bin/featureUtility installServerFeatures SERVERNAME

/liberty/wlp/bin/installUtility install SERVERNAME

After this it should be possible to start the server SERVERNAME successfully.

Connect to it using the url http://localhost/SERVERNAME/xyz-servlet

(where the name of the servlet can be found in the index.jsp file auto-generated for you by the IDE when you created the servlet project).