API First

✅ Use Case: Customer Management Service (API First)

Step 1: Define API Contract (OpenAPI/Swagger)

Here’s an example openapi.yaml:

openapi: 3.0.1

info:

title: Customer API

description: API for managing customers

version: 1.0.0

servers:

- url: http://localhost:8080

paths:

/customers:

get:

summary: Get all customers

responses:

'200':

description: List of customers

content:

application/json:

schema:

type: array

items:

$ref: '#/components/schemas/Customer'

post:

summary: Create a customer

requestBody:

required: true

content:

application/json:

schema:

$ref: '#/components/schemas/Customer'

responses:

'201':

description: Customer created

/customers/{id}:

get:

summary: Get customer by ID

parameters:

- name: id

in: path

required: true

schema:

type: string

responses:

'200':

description: Customer details

content:

application/json:

schema:

$ref: '#/components/schemas/Customer'

'404':

description: Customer not found

components:

schemas:

Customer:

type: object

properties:

id:

type: string

name:

type: string

email:

type: string

phone:

type: string

Step 2: Generate Code from OpenAPI

You can generate Spring Boot server stubs using OpenAPI Generator:

bash

openapi-generator-cli generate \

-i openapi.yaml \

-g spring \

-o customer-service \

--additional-properties=interfaceOnly=true

Step 3: Implement the Interfaces

In the generated code, implement the controller logic in classes like:

@RestController

public class CustomerApiController implements CustomerApi {

@Override

public ResponseEntity<List<Customer>> getCustomers() {

// Example data

List<Customer> customers = List.of(

new Customer("1", "Alice", "alice@example.com", "1234567890"),

new Customer("2", "Bob", "bob@example.com", "0987654321")

);

return ResponseEntity.ok(customers);

}

@Override

public ResponseEntity<Customer> getCustomerById(String id) {

Customer customer = new Customer(id, "Alice", "alice@example.com", "1234567890");

return ResponseEntity.ok(customer);

}

@Override

public ResponseEntity<Void> createCustomer(Customer customer) {

System.out.println("Creating customer: " + customer);

return new ResponseEntity<>(HttpStatus.CREATED);

}

}

Step 4: Test the API

• Start the Spring Boot app

• Use Swagger UI or Postman to test endpoints

• Use SpringDoc OpenAPI for in-app Swagger UI:

xml

<dependency>

<groupId>org.springdoc</groupId>

<artifactId>springdoc-openapi-ui</artifactId>

<version>1.7.0</version>

</dependency>

Perfect! Let's now integrate the Spring Boot API-First Customer Service into a full Azure DevOps CI/CD pipeline, complete with Dockerization, deployment to Azure Kubernetes Service (AKS), and use of Azure Container Registry (ACR).

🔧 Step 1: Dockerize the Spring Boot Application

📄 Dockerfile

FROM openjdk:17-jdk-slim

VOLUME /tmp

ARG JAR_FILE=target/customer-service-0.0.1-SNAPSHOT.jar

COPY ${JAR_FILE} app.jar

ENTRYPOINT ["java","-jar","/app.jar"]

🏗️ Step 2: Azure DevOps Pipeline (YAML)

📄 azure-pipelines.yml

yaml

trigger:

branches:

include:

- main

variables:

dockerRegistryServiceConnection: 'AzureContainerRegistryConnection'

imageRepository: 'customer-service'

containerRegistry: 'myacr.azurecr.io'

dockerfilePath: 'Dockerfile'

tag: '$(Build.BuildId)'

stages:

- stage: Build

displayName: Build and Push Image

jobs:

- job: Build

displayName: Build

pool:

vmImage: 'ubuntu-latest'

steps:

- task: Maven@3

inputs:

mavenPomFile: 'pom.xml'

goals: 'clean package'

options: '-DskipTests'

- task: Docker@2

inputs:

containerRegistry: '$(dockerRegistryServiceConnection)'

repository: '$(imageRepository)'

command: 'buildAndPush'

Dockerfile: '$(dockerfilePath)'

tags: |

$(tag)

- stage: Deploy

displayName: Deploy to AKS

dependsOn: Build

jobs:

- deployment: Deploy

displayName: Deploy to AKS

environment: 'aks-env'

pool:

vmImage: 'ubuntu-latest'

strategy:

runOnce:

deploy:

steps:

- task: Kubernetes@1

inputs:

connectionType: 'Azure Resource Manager'

azureSubscription: '<Your Azure Subscription>'

azureResourceGroup: '<Your Resource Group>'

kubernetesCluster: '<Your AKS Cluster>'

namespace: 'default'

command: apply

useConfigurationFile: true

configuration: |

manifests/deployment.yaml

📦 Step 3: Kubernetes Deployment YAML

📄 manifests/deployment.yaml

yaml

apiVersion: apps/v1

kind: Deployment

metadata:

name: customer-service

spec:

replicas: 2

selector:

matchLabels:

app: customer-service

template:

metadata:

labels:

app: customer-service

spec:

containers:

- name: customer-service

image: myacr.azurecr.io/customer-service:latest

ports:

- containerPort: 8080

env:

- name: SPRING_PROFILES_ACTIVE

value: "prod"

---

apiVersion: v1

kind: Service

metadata:

name: customer-service

spec:

type: LoadBalancer

selector:

app: customer-service

ports:

- protocol: TCP

port: 80

targetPort: 8080

🔐 Step 4: Security & Integration

Component	Integration
Azure AD	Use Spring Boot OAuth2 Client for auth with Azure AD
ACR	Docker images pushed via Azure DevOps
AKS + Istio	Secure mTLS, route policies, observability
Secrets Management	Mount Azure Key Vault as volume or inject via env vars
Monitoring	Use Azure Monitor, Prometheus, Grafana for AKS metrics

✅ Optional Enhancements

• Add SonarQube for code quality

• Add JUnit + JaCoCo for test + coverage

• Use Helm charts instead of raw YAML

• Add a separate test stage with automated integration tests

Would you like me to:

• Generate the complete Helm chart for this?

• Add Spring Security config for Azure AD login?

• Or create an architecture diagram including DevOps + AKS?

Let me know how deep you'd like to go!

You said:

how api deisgn is being used for testing contract

ChatGPT said:

Great question! In API-First Design, the OpenAPI contract (typically a .yaml or .json file) is the single source of truth — and this enables contract testing between frontend/backend or between services.

🧪 How API-First Design Enables Contract Testing

1. ✅ Consumer-Driven Contract Testing

Tools like Pact allow teams to:

• Define how the consumer expects the provider to behave.

• Test whether the provider adheres to that contract.

💡 Works great in microservices when a frontend or one microservice depends on another.

2. 🧾 Validation of Implementation Against OpenAPI

Use tools like:

• Swagger Codegen / OpenAPI Generator to scaffold servers or clients.

• Swagger Request Validator or Spring Cloud Contract to validate actual behavior against spec.

3. 🔧 Spring Boot + OpenAPI + Contract Validation

Let’s say you’ve defined your OpenAPI spec openapi.yaml.

✅ Example: Test Contract Using spring-cloud-contract

Step 1: Add Dependency

xml

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<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-contract-verifier</artifactId> <version>4.0.1</version> </dependency>

Step 2: Create a Contract Stub (.groovy file)

groovy

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Contract.make { request { method 'GET' url '/customers/1' } response { status 200 body([ id: "1", name: "Alice", email: "alice@example.com" ]) headers { contentType(applicationJson()) } } }

Step 3: Generate Tests

bash

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./mvnw clean install

This will generate JUnit tests validating that your implementation matches the contract.

🔬 Additional Tools for Contract Testing

Tool	Purpose
Pact	Consumer-driven contract testing
Postman/Newman	Contract-based API testing from OpenAPI
Dredd	Executes tests defined in OpenAPI spec
RestAssured + OpenAPI Validator	Validates HTTP responses against OpenAPI
Spring Cloud Contract	Stubs and verifies contract using Groovy DSL

🧰 CI/CD Integration

In an Azure DevOps pipeline:

1. Validate OpenAPI syntax

2. Generate contract tests

3. Run them in a build step

4. Optionally publish stubs (e.g., Pact Broker) for consumers