Dockerizing A SpringBoot Application

This short article will show you how to create a Docker Container from a SpringBoot application. A sample project is commited on Github. Click here to check the project.

Prerequisites:

• Docker must be installed on your machine.
• You have basic knowledge of SpringBoot and Docker Concepts

A Very Short Introduction

DOCKER is a tool to make it easier to build, deploy, and run applications in an isolated environment called CONTAINERS.

CONTAINERS allow a developer to package up an application with all of its dependencies, and ship it as one package.

For Java Developers and JVM the slogan is "Write Once Run Anywhere" while for Docker and Containers we can say "Package Once Deploy Anywhere".

If you want to learn more please checkout Docker Official Documents. It is very helpfull.

Docker CLI – image commands

docker image [COMMAND]

• build : Build an image.
• push : Push an image to a remote registry.
• ls : List images.
• history : See intermediate image info.
• inspect : See lots of info about an image, including the layers.
• rm : Delete an image.

Docker CLI – container commands

docker container [COMMAND]

• create : Create a container from an image.
• start : Start an existing container.
• run : Create a new container and start it.
• ls : List running containers.
• inspect : See lots of info about a container.
• logs : Print logs.
• stop : Gracefully stop running container.
• kill : Stop main process in container abruptly.
• rm : Delete a stopped container.

Why We Are Containerizing An Application ?

Because it solves a lot of problem that we are facing during our day-to-day work as a developer. Below is a list of benefits that i am touching briefly.

• A Container eliminates it works on my machine problem by providing a runnable isolated package of an application.
• Portability : Since Docker containers encapsulate everything an application needs to run (and only those things), they allow applications to be shared easily between environments.
• Efficient use of resources : Instances of containerized apps use far less memory than virtual machines, they start up and stop more quickly.
• Fast Application Delivery : Containers carry the minimal runtime requirements of an application, decreasing its size and enabling them to be deployed instantly.
• Rapid creation of development environments.
• Ecosystem (Docker Hub, Other Registeries).

** In the next chapters I will be writing down the steps required for creating a containerized SpringBoot application using Docker. **

Step - 1 Updating pom.xml in the project

The first step is adding SpringBoot maven plugin into the pom.xml file in your project.

By doing so you can create executable jar file of your SpringBoot application.

After adding the lines below. You can run mvn clean package command. This command will generate the jar file in the target folder.

<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
		<finalName>docker-springboot</finalName>
</build>

Step - 2 Create A Dockerfile

Create a Dockerfile in the root directory of your project.

Docker can build images automatically by reading the instructions from a Dockerfile.

The Dockerfile is essentially the build instructions to build the image.

# Dockerfile for our SpringBoot application
# Set the baseImage to use for subsequent instructions.
# FROM must be the first instruction in a Dockerfile.
# jdk-alpine is the minimal image for running jar files
FROM openjdk:jdk-alpine

# Add maintainer info
LABEL maintainer = "mrgenco"

# Copy files, folders, or remote URLs from source to the dest path in the filesystem.
ADD target/docker-springboot.jar docker-springboot.jar

# Define the network ports that this container will listen on at runtime.8080
EXPOSE 8080

# Configures the container to be run as an executable.
ENTRYPOINT ["java", "-jar", "docker-springboot.jar"]

Step - 3 Create An Image

The next step is to create an Image using your Dockerfile. In terminal you need to navigate to the same directory where your Dockerfile exists.

docker image build -t mrgenco-springboot-image .

Step - 4 Run The Container

After creating your image the last step is Running a Container using your created image.

docker container run -it -p 8085:8080 --name mrgenco-springboot-container mrgenco-springboot-image

Thanks for reading!