docker java application

Docker Java Application Example: Build and Run a Java App Step-by-Step Guide to Creating, Dockerizing, and Running a Java Application

Introduction • Docker provides a convenient way to package and run Java applications inside isolated containers.

• Learn how to run a Java application using Docker • Create a simple Java program • Write a Dockerfile for the application • Build and run a Docker image • Understand the Java + Docker workflow

Create a Java Application Step 1: Create a project directory

• mkdir java-docker-app • cd java-docker-app Step 2: Create Hello.java

• class Hello { • public static void main(String[] args) { • System.out.println("Hello from Java and Docker"); • } • }

Create a Dockerfile Create a file named Dockerfile in the same directory.

• FROM java:8 • COPY . /var/www/java • WORKDIR /var/www/java • RUN javac Hello.java • CMD ["java", "Hello"] What these instructions do:

• FROM → Selects the base Java image • COPY → Copies the Java application • WORKDIR → Sets the working directory • RUN → Compiles the Java source • CMD → Runs the Java application

Build the Docker Image Use the following command:

• docker build -t java-app .

• Understanding the command: • docker build → Builds a Docker image • -t java-app → Assigns a name to the image • . → Uses the current directory as the build context • Once the build finishes, the Java application is packaged into a Docker image.

Run the Java Application Once the Docker image has been created, run it as a container using:

• docker run java-app What happens?

• Docker creates a container from the image.

• The Java application starts inside the container.

• The program displays its output in the terminal.

• The application runs in an isolated environment.

• Workflow:

Java Code → Dockerfile → Docker Image → Container → Output

Conclusion

• Docker makes it simple to package and run Java applications in a consistent environment.