How to configure environment variables in Spring Boot via Kubernetes (ConfigMap/Secrets)?

In Kubernetes, ConfigMap and Secrets are commonly used to pass configuration data and secrets to a Spring Boot application, mounted as environment variables.

To configure environment variables via ConfigMap/Secrets, you need to:

1. Create a ConfigMap or Secret with the required keys and values.

Example ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  SPRING_DATASOURCE_URL: jdbc:mysql://db:3306/mydb
  SPRING_DATASOURCE_USERNAME: user

2. In the Deployment manifest, add these data as environment variables in the container:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-app
spec:
  template:
    spec:
      containers:
      - name: app
        image: my-spring-app:latest
        envFrom:
        - configMapRef:
            name: app-config
        - secretRef:
            name: app-secrets

3. In the Spring Boot application, environment variables are automatically picked up thanks to naming conventions (for example, SPRING_DATASOURCE_URL corresponds to the property spring.datasource.url).

Thus, you can centrally manage configuration and secrets outside the application image, which is convenient for different environments and secure for sensitive data.