Docker is a set of platform as a service products that use OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels. This post is a simple tutorial on how you can Dockerize a Spring Boot Application and run it as a container.
The easiest way to Dockerize a Spring Boot Application is to use a simple Dockerfile in your project. A few weeks ago, I wrote a tutorial on how to use Swagger with Spring Boot. I have used the same code and Dockerized it. Also, make sure you have Docker installed.
#1. Create a Dockerfile
The first step that you need to do is create a Dockerfile in your Project root.
When you create the Docker image, this basically will run the application using non-root privilege.
FROM openjdk:8-jdk-alpine
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]
#2. Build the Docker image
To build the Docker image, go to the same directory where Dockerfile is present. Run the below command.
$ docker build -t spring-boot-swagger-docker .
Sending build context to Docker daemon 25.4MB
Step 1/6 : FROM openjdk:8-jdk-alpine
8-jdk-alpine: Pulling from library/openjdk
e7c96db7181b: Pull complete
f910a506b6cb: Pull complete
c2274a1a0e27: Pull complete
Digest: sha256:94792824df2df33402f201713f932b58cb9de94a0cd524164a0f2283343547b3
Status: Downloaded newer image for openjdk:8-jdk-alpine
---> a3562aa0b991
Step 2/6 : RUN addgroup -S spring && adduser -S spring -G spring
---> Running in 640f6bdd803d
Removing intermediate container 640f6bdd803d
---> 6c8dedc4ddaf
Step 3/6 : USER spring:spring
---> Running in 8a18e5479e13
Removing intermediate container 8a18e5479e13
---> 5d6a633ec222
Step 4/6 : ARG JAR_FILE=target/*.jar
---> Running in 9b3a87c9561c
Removing intermediate container 9b3a87c9561c
---> 9fa6b15f0fd4
Step 5/6 : COPY ${JAR_FILE} app.jar
---> b75ce446dac4
Step 6/6 : ENTRYPOINT ["java","-jar","/app.jar"]
---> Running in 3571f355d675
Removing intermediate container 3571f355d675
---> 677535798fce
Successfully built 677535798fce
Successfully tagged spring-boot-swagger-docker:latest
To check if the image has been created, run the below command.
$ docker images -a REPOSITORY TAG IMAGE ID CREATED SIZE spring-boot-swagger-docker latest 677535798fce 9 hours ago 130MB <none> <none> b75ce446dac4 9 hours ago 130MB <none> <none> 9fa6b15f0fd4 9 hours ago 105MB <none> <none> 5d6a633ec222 9 hours ago 105MB <none> <none> 6c8dedc4ddaf 9 hours ago 105MB openjdk 8-jdk-alpine a3562aa0b991 20 months ago 105MB
#3. Run the container
To run the container, use the below command. This will run your application on port 8090.
$ docker run -p 8090:8080 spring-boot-swagger-docker
To check if your container is running, use the below command.
$ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS ac5c8ee39b32 spring-boot-swagger-docker "java -jar /app.jar" About a minute ago Up About a minute 0.0.0.0:8090->8080/tcp
You can now check on your local browser by verifying if the Swagger UI loads up.
So, that’s it for this tutorial. Stay tuned for more.
