Containerize Spring Boot Application Using Docker

Containerization has become a popular approach for software deployment due to its numerous benefits, such as increased scalability, portability, and flexibility. Spring Boot, a widely used Java framework for building web applications, can also be containerized to simplify deployment and management. In this article, we will discuss the steps to containerize a Spring Boot application.

1. Build your Spring Boot application Before containerizing your Spring Boot application, you need to ensure that it is properly built and can run as a standalone application. You can use a build tool like Maven or Gradle to create a package of your application.

mvn clean package

Run above command on your terminal and then go to the target directory. You can also run your application using the command

java -jar docker-demo-0.0.1-SNAPSHOT.jar

to ensure that it is working correctly.

2. Create a Dockerfile A Dockerfile is a script that contains instructions for building a Docker image. You can create a Dockerfile in the root directory of your project. Here’s a basic example:

FROM openjdk:18-jdk-alpine
COPY target/docker-demo-0.0.1-SNAPSHOT.jar /app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

The first line specifies the base image, which in this case is the official OpenJDK image. The second line copies the application package to the Docker image. Finally, the entry point specifies the command to run when the container starts.

3. Build the Docker image Once you have created the Dockerfile, you can use the Docker CLI to build the Docker image. Navigate to the directory containing the Dockerfile and run the following command:

docker build -t docker-demo:1 .

The “-t” option specifies the name and tag of the image. The “.” specifies the build context, which is the directory containing the Dockerfile.

4. Run the Docker container After building the Docker image, you can run the container using the following command:

docker run -p 8090:8090 docker-demo:1

The “-p” option maps the host port to the container port. The “<image-name>:<tag>” specifies the name and tag of the image you want to run.

5. Test your containerized application Once the container is running, you can test your application by accessing it through a web browser or using a tool like cURL. If you see the expected output, congratulations, you have successfully containerized your Spring Boot application!

In conclusion, containerizing your Spring Boot application can simplify deployment and management. By following the steps outlined in this article, you can easily create a Docker image of your application and run it in a container.

However, there are some best practices you should follow to optimize the containerization process. Here are a few tips:

1. Keep the container small One of the primary benefits of containerization is the ability to create lightweight and portable containers. To achieve this, you should aim to keep the container as small as possible. For example, you can use a minimal base image like Alpine Linux and remove unnecessary packages and files.
2. Use environment variables To make your container more flexible and configurable, you can use environment variables. This allows you to easily change the behavior of your application without modifying the Dockerfile. You can set environment variables using the “-e” option when running the container.
3. Use a container orchestration tool As your application grows, managing containers manually can become challenging. Container orchestration tools like Kubernetes or Docker Swarm can help automate the process of deploying and managing containers at scale.
4. Secure your container Container security is a critical aspect of containerization. Ensure that you use secure base images, keep your container updated with security patches, and use best practices for securing the application within the container.

In summary, containerizing your Spring Boot application can provide many benefits, including increased portability, scalability, and flexibility. By following the best practices outlined in this article, you can create efficient and secure containerized applications.

source code : https://github.com/rragul/docker-demo