Deploying Spring Boot Applications with Spring Boot Operator on Kubernetes

Deploying a Spring Boot application on Kubernetes can be complex, but the Spring Boot Operator simplifies the process by extending the Kubernetes API with custom resource definitions (CRDs).

Package Docker Image – Use the Google Jib Maven plugin to build and push a Docker image directly from the project without a Dockerfile:

mvn com.google.cloud.tools:jib-maven-plugin:build \
  -Djib.to.auth.username=${{ secrets.MY_USERNAME }} \
  -Djib.to.auth.password=${{ secrets.MY_PASSWORD }} \
  -Djib.container.jvmFlags=--add-opens=java.base/sun.nio.ch=ALL-UNNAMED \
  -Djib.from.image=freemanliu/oprenjre:11.0.5 \
  -Dimage=registry.cn-shanghai.aliyuncs.com/qingmuio/operator-demo/operator-demo:v1.0.0

After the command finishes, the image is pushed to the remote registry.

Install the Operator – Apply the operator manifests to the cluster (a ready Kubernetes cluster is required):

kubectl apply -f https://raw.githubusercontent.com/goudai/spring-boot-operator/master/manifests/deployment.yaml

The console shows the creation of the namespace, CRD, roles, and the operator deployment.

Deploy the Demo Application – Create a CRD yaml (Demo.yaml) that describes the Spring Boot application and apply it:

# Demo.yaml
apiVersion: springboot.qingmu.io/v1alpha1
kind: SpringBootApplication
metadata:
  name: operator-demo
spec:
  springBoot:
    version: v1.0.0
    # image: registry.cn-shanghai.aliyuncs.com/qingmuio/operator-demo/operator-demo:v1.0.0

kubectl apply -f Demo.yaml

Verify the pod is running and the service is exposed:

kubectl get po -n spring-boot-operator-system
kubectl get svc | grep operator-demo

Test the endpoint:

curl -i http://10.101.128.6:8080

Scale the Application – Edit Demo.yaml to add a replicas: 1 field and re‑apply:

spec:
  springBoot:
    version: v1.0.0
    replicas: 1

kubectl apply -f Demo.yaml

Check that only one pod remains.

Cleanup – Delete the demo resources:

kubectl delete -f Demo.yaml

Deploy Your Own Application – Create a Docker‑registry secret if needed, then write a full CRD yaml that includes image, replicas, resource limits, health paths, and optional imagePullSecrets:

apiVersion: springboot.qingmu.io/v1alpha1
kind: SpringBootApplication
metadata:
  name: my-app
spec:
  springBoot:
    version: v1.0.0
    image: registry.cn-shanghai.aliyuncs.com/qingmuio/my-app:v1.0.0
    replicas: 2
    resource:
      cpu:
        request: 50m
      memory:
        request: 1Gi
    liveness: /actuator/health
    readiness: /actuator/health
    shutdown: /spring/shutdown
    imagePullSecrets:
      - aliyun-registry-secret

kubectl apply -f MyApp.yaml

Graceful Shutdown – Enable the shutdown endpoint in application.yml and expose it via a controller:

management:
  endpoints:
    web:
      exposure:
        include: "*"
  endpoint:
    shutdown:
      enabled: true

@RestController
public class ShutdownController {
    @Autowired
    private ShutdownEndpoint shutdownEndpoint;

    @GetMapping("/spring/shutdown")
    public Map
shutdown(HttpServletRequest request) {
        return shutdownEndpoint.shutdown();
    }
}

Node Affinity – Label nodes with zones (e.g., cn‑i, cn‑h, cn‑g) and set affinity in the CRD to distribute pods across zones:

kubectl label node node-i1 failure-domain.beta.kubernetes.io/zone=cn-i
kubectl label node node-i2 failure-domain.beta.kubernetes.io/zone=cn-i
# repeat for other zones

spec:
  springBoot:
    nodeAffinity:
      key: "failure-domain.beta.kubernetes.io/zone"
      operator: "In"
      values:
        - "cn-i"
        - "cn-h"
        - "cn-g"

Custom Operator Installation – Modify the operator deployment yaml to inject environment variables that control image repository, CPU/memory requests, health check paths, replica count, log paths, and global Spring Boot environment variables. Example fragment:

- name: IMAGE_REPOSITORY
  value: registry.cn-shanghai.aliyuncs.com/qingmuio
- name: REQUEST_CPU
  value: 50m
- name: REQUEST_MEMORY
  value: 500Mi
- name: READINESS_PATH
  value: /actuator/health
- name: SHUTDOWN_PATH
  value: /spring/shutdown
- name: REPLICAS
  value: "3"
- name: SPRING_BOOT_ENV
  value: "EUREKA_SERVERS=http://eureka1:8761/eureka/,http://eureka2:8761/eureka/"

After editing, apply the deployment to update the operator.

For more details, refer to the GitHub repository SpringBootOperator .