Building and Running a Java Application with Dockerfile

This article demonstrates how to containerize a Java application by creating a Dockerfile and using Docker commands.

Step 1: Prepare the Dockerfile – Place the JAR file in an empty directory and create a Dockerfile with the following essential instructions:

FROM <image_name>:<tag>

RUN <linux_command_to_build_or_prepare>

COPY [--chown=<user>:<group>] <source_path>... <destination_path>

CMD nohup java -jar xxxx.jar > xxx.log 2>&1 &

The FROM line defines the base image (e.g., nginx or a JDK image). RUN executes commands during the image build, either in shell form ( RUN <command>) or exec form ( RUN ["executable", "arg1", "arg2"]). COPY copies files from the build context into the image, and CMD specifies the default command that runs when the container starts (it can be overridden at docker run time). Note that if multiple CMD statements exist, only the last one takes effect.

Step 2: Example Dockerfile for the Java app

EXPOSE 8031

ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

Step 3: Build the image docker build -t haha-shen-standard . Step 4: Run the container

First attempt (may fail if the port is occupied):

docker run -d --restart=always --name haha-shen-standard -v /usr/local/apps/haha-shen-standard/logs:/opt/java/logs -p 8080:8031 haha-shen-standard

If the port is in use, change the host port and container name:

docker run -d --restart=always --name haha-shen-standard01 -v /usr/local/apps/haha-shen-standard/logs/:/opt/java/logs/ -p 8081:8031 haha-shen-standard

After the container starts, you can verify it with: docker ps -a and view its logs: docker logs --tail 100 -f haha-shen-standard01 This workflow provides a complete end‑to‑end example of containerizing a Java JAR, building the image, running it with persistent log storage, and troubleshooting common issues such as port conflicts.