1. Introduction
Spring Boot is a popular framework for building microservices and standalone applications. Docker provides containerization for consistent environments, while Kubernetes offers orchestration and management at scale.
2. Setting Up Your Spring Boot Application
2.1 Creating a Sample Spring Boot Application
Let's create a simple Spring Boot application to demonstrate the deployment process.
Use Spring Initializr (https://start.spring.io) to create a new project with dependencies for Spring Web and Spring Boot DevTools. Name the project demo.
2.2 Define the Application
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
2.3 Create a Simple REST Controller
package com.example.demo;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/api")
public class GreetingController {
@GetMapping("/greet")
public String greet() {
return "Hello, World!";
}
}
2.4 Build the Application
Run the following command to build the application:
./mvnw clean package
3. Dockerizing the Spring Boot Application
3.1 Create a Dockerfile
Create a file named Dockerfile in the root of your project:
# Use the official OpenJDK image
FROM openjdk:17-jdk-slim
# Set the working directory
WORKDIR /app
# Copy the JAR file into the container
COPY target/demo-0.0.1-SNAPSHOT.jar app.jar
# Run the JAR file
ENTRYPOINT ["java", "-jar", "/app/app.jar"]
3.2 Build the Docker Image
docker build -t demo-app .
3.3 Run the Docker Container
Run the Docker container with the following command:
docker run -p 8080:8080 demo-app
3.4 Verify the Application
Open your browser or use curl to check if the application is running:
curl http://localhost:8080/api/greet
You should see the response: Hello, World!.
4. Deploying on Kubernetes
4.1 Create Kubernetes Deployment and Service Files
Create a deployment.yaml file:
apiVersion: apps/v1
kind: Deployment
metadata:
name: demo-app
spec:
replicas: 2
selector:
matchLabels:
app: demo-app
template:
metadata:
labels:
app: demo-app
spec:
containers:
- name: demo-app
image: demo-app:latest
ports:
- containerPort: 8080
Create a service.yaml file:
apiVersion: v1
kind: Service
metadata:
name: demo-app-service
spec:
selector:
app: demo-app
ports:
- protocol: TCP
port: 80
targetPort: 8080
type: LoadBalancer
4.2 Deploy to Kubernetes
Apply the Deployment and Service:
Read more at : Spring Boot Applications with Docker and Kubernetes
Top comments (0)