Dockerizing Java 17 and Gradle: A Step-by-Step Guide

Docker has become an essential tool in modern software development, allowing developers to package applications and their dependencies into containers that can run consistently across different environments. In this article, we'll explore the process of dockerizing a Java 17 and Gradle application to facilitate easy deployment and ensure consistency in various environments.

Prerequisites

Before you begin, make sure you have Docker installed on your machine. You can download and install Docker from the official Docker website.

Understanding the Dockerfile

Let's start by examining the provided Dockerfile:

FROM gradle:jdk17-jammy AS BUILD
WORKDIR /usr/app/
COPY . .
RUN gradle test -i
RUN gradle --no-daemon build

CMD ["gradle", "run", "-q", "--console=plain"]

Here's a breakdown of each section:

FROM gradle:jdk17-jammy AS BUILD
Specifies the base image to use, which is based on Gradle and Java 17.

WORKDIR /usr/app/
Sets the working directory inside the container to /usr/app/.

COPY . .
Copies the current directory (containing your application code) to the working directory in the container.

RUN gradle test -i
Executes the Gradle test task with the -i flag for detailed logging.

RUN gradle --no-daemon build
Builds the Gradle project without using the daemon.

CMD ["gradle", "run", "-q", "--console=plain"]
Specifies the default command to run when the container starts. In this case, it runs the gradle run task quietly with a plain console output.

Building the Docker Image

To build the Docker image, navigate to the directory containing your Dockerfile and run the following command:

docker build -t my-java-gradle-app .

This command builds an image with the tag my-java-gradle-app. Make sure to replace it with a tag of your choice.

Running the Docker Container

Once the image is built, you can run a container using the following command:

docker run my-java-gradle-app

This will execute the default CMD specified in the Dockerfile (gradle run -q --console=plain), and your Java 17 and Gradle application will run inside the Docker container.

Customizing the Dockerfile

Depending on your specific requirements, you may need to customize the Dockerfile. For example, if your application requires additional dependencies or configuration, you can modify the Dockerfile accordingly.

Additionally, consider using a multi-stage build to create a smaller production image. This involves using a separate image for the final production container, which only includes the necessary artifacts from the build stage.

Conclusion

Dockerizing Java 17 and Gradle applications simplifies the deployment process and ensures consistency across different environments. With the provided Dockerfile as a starting point, you can easily adapt it to suit your specific project requirements. Docker's versatility and containerization benefits make it a valuable tool in the modern development workflow.