Developing a Connect application

Learn how to create and structure Connect applications.

What are Connect applications?

Connect applications are the applications that are hosted and run by Connect once their associated Connector has been published. Connect applications can be developed using JavaScript/TypeScript or Java.

Follow this guide to learn how to structure your Connect application for use in a Connector. Links to starter templates are also provided.

Requirements

Developing Connect applications requires a commercetools Composable Commerce Project and a GitHub account. The following requirements are based on whether you are developing Connect applications using JavaScript/TypeScript or Java.

JavaScript/TypeScript

  • Node v16.x LTS (or later)
  • npm or Yarn

Java

  • Java v11 LTS (or later - v17 LTS is preferred)
  • Maven
  • Knowledge of the Spring Boot framework

It is currently recommended to create Connect applications using JavaScript or TypeScript. For more information about creating Connect applications with Java, contact the Connect support team.

Use a template

You can develop Connect applications with ease using one of the starter or application templates. Starter templates provide boilerplate code and folder structures for creating generic Connect applications. To create applications for dedicated use cases, you can use the application templates.

  • Starter templates: To use a starter template, do the following:

    1. Install the Create Connect App.

      npm install --global @commercetools-connect/create-connect-app
    2. Install a template for JavaScript or TypeScript.

    create-connect-app first-connect-application --template javascript
    create-connect-app first-connect-application --template typescript
  • Application templates: To use an application template, fork one of the following GitHub repositories based on your use case:

Use the correct directory structure

You should structure your Connect application as in the following example. The following directory structure is reflected in the starter templates.

├── < docs >
│ └── readme.md
├── < event >
│ ├── src
│ ├── tests
│ └── package.json
├── < job >
│ ├── src
│ ├── tests
│ └── package.json
├── < service >
│ ├── src
│ ├── tests
│ └── package.json
├── < merchant-center-custom-application >
│ ├── src
│ ├── tests
│ └── package.json
├── < assets >
│ ├── src
│ ├── tests
│ └── package.json
└── connect.yaml

The folders event, job, service, merchant-center-custom-application, and assets represent the possible Connect application types that can be run in your Connector. You can remove folders of applications you do not want to develop, or you can rename them to reflect the Connect application's purpose. A Connector can have one or more Connect applications of the same type.

You must specify the deployment information of your Connect applications in connect.yaml. This file contains information that is required to create, publish, and deploy Connect applications.

Configure connect.yaml

connect.yaml is located in the root of the Connect application and contains the necessary configuration and scripts for it to operate. The following example connect.yaml file is found in the starter template.

Example connect.yamlyaml
deployAs:
- name: service
applicationType: service
endpoint: /service
scripts:
postDeploy: npm install && npm run connector:post-deploy
preUndeploy: npm install && npm run connector:pre-undeploy
configuration:
standardConfiguration:
- key: CTP_PROJECT_KEY
description: Project key of the commercetools Composable Commerce Project
required: true
default: 'default-key'
- key: CTP_REGION
description: Region where the Composable Commerce Project is hosted
required: true
securedConfiguration:
- key: CTP_CLIENT_ID
description: client_id of an API Client for the Composable Commerce Project
required: true
- key: CTP_CLIENT_SECRET
description: secret of an API Client for the Composable Commerce Project
required: true
- key: CTP_SCOPE
description: scope of an API Client for the Composable Commerce Project
- name: job
applicationType: job
endpoint: /job
properties:
schedule: '*/5 * * * *'
configuration:
standardConfiguration:
- key: CTP_PROJECT_KEY
description: Project key of the Composable Commerce Project
required: true
default: 'default-key'
- key: CTP_REGION
description: Region where the Composable Commerce Project is hosted
required: true
securedConfiguration:
- key: CTP_CLIENT_ID
description: client_id of an API Client for the Composable Commerce Project
required: true
- key: CTP_CLIENT_SECRET
description: secret of an API Client for the Composable Commerce Project
required: true
- key: CTP_SCOPE
description: scope of an API Client for the Composable Commerce Project
- name: event
applicationType: event
endpoint: /event
scripts:
postDeploy: npm install && npm run connector:post-deploy
preUndeploy: npm install && npm run connector:pre-undeploy
configuration:
standardConfiguration:
- key: CTP_PROJECT_KEY
description: Project key of the Composable Commerce Project
required: true
default: 'default-key'
- key: CTP_REGION
description: Region where the Composable Commerce Project is hosted
required: true
securedConfiguration:
- key: CTP_CLIENT_ID
description: client_id of an API Client for the Composable Commerce Project
required: true
- key: CTP_CLIENT_SECRET
description: secret of an API Client for the Composable Commerce Project
required: true
- key: CTP_SCOPE
description: scope of an API Client for the Composable Commerce Project
- name: merchant-center-custom-application
applicationType: merchant-center-custom-application
configuration:
standardConfiguration:
- key: CUSTOM_APPLICATION_ID
description: The Custom Application ID
required: true
- key: CLOUD_IDENTIFIER
description: The cloud identifier
default: 'gcp-eu'
- key: ENTRY_POINT_URI_PATH
description: The Application entry point URI path
required: true
- name: assets
applicationType: assets

The values of connect.yaml are as follows.

KeyDescription
nameIdentifier of the application deployment. The Deployment's output URL, topic, and schedule are fetched based on this reference. name must match the folder for the application in your repository. name has a maximum length of 256 characters and can only contain the letters A to Z in lowercase or uppercase, numbers, underscores (_), and the hyphen-minus (-).
applicationTypeCan be event, job, service, merchant-center-custom-application or assets.
endpointThe endpoint naming used by the Deployment URL. The URL is constructed using the format {connect-provided-url}/{endpoint} (for example: https://service-11111111-1111-1111-1111-111111111111.europe-west1.gcp.commercetools.app/service). endpoint can optionally start with / and has a maximum length of 256 characters containing the letters A to Z in lowercase or uppercase, numbers, underscores (_), and the hyphen-minus (-). endpoint is not required if the applicationType is merchant-center-custom-application or assets.
configurationDefines the standard and secret environment variables needed by the Connect application. The client defines values for these environment variables when deploying the Connector. If required is true, a value for the environment variable must be included. Default values can only be specified for standard environment variables and will be used as fallback values if not provided during deployment. configuration is not required for assets.
propertiesPlaceholder for all additional arguments in hosting a Connector. Currently supports a schedule for job applications.
properties.scheduleCron expression for job applications.

event applications use a message broker service provisioned during deployment. Messages received by the queue are delivered to event applications to process. job applications use a scheduler service provisioned during deployment. Scheduler services triggers the job application based on the cron expression defined in properties.schedule.

Manage the application with Yarn commands

Use the following Yarn commands to manage your Connect application.

Install dependencies

Dependencies are installed using Yarn Workspaces.

yarn

Run tests

yarn test
# or
yarn test:watch

Build the application

yarn build
# or
yarn build:watch

Run the application locally

yarn start
# or
yarn start:dev

Testing your Connect application

It is recommended to implement unit and integration test cases as part of application development and follow a test-driven development approach.

These test cases are reviewed and also executed during the publishing process. Scripts to run tests should be defined in a test script.

Connect application templates provide sample implementation of testing using Jest.

Upload and create a release on GitHub

After finishing the development of a Connect application, you should push it to a GitHub repository. The Connect application should be released on GitHub with a Git tag so that specific application releases can be referenced by the Connector.

Your GitHub repository can be public or private. If you are using a private repository, you must provide access to the GitHub machine user connect-mu before publishing your Connector.

Next steps

Once your Connect application, GitHub repository, and Git tag are ready, you can follow our getting started guide to create a Connector using your Connect application.