Running java application using docker

Maven build and containerize java application

Before Starting

• I have wsl2 installed in my system and I am using my Linux environment to run this application. I also advised developers to use Linux environment as we will be going to use lot of command line stuff later.

Software needed : Java Maven VS Code Linux in WSL2

Maven build

In the previous step, we run our application normally. Now its time to do the maven build (using mvnw) and then make its docker container and try to run the application from inside of our container.

In the root directory of your project, run this command - ./mvnw -Dmaven.test.skip=true spring-boot:build-image

Note : If while running this command ./mvnw -Dmaven.test.skip=true spring-boot:build-image if it is showing error no such file or directory, its a wsl 2 problem. In wsl2, mvnw is still not working sometimes due to windows issue, so run this -

sudo apt install dos2unix
dos2unix mvnw

Now your mvnw will works properly.

This command will create a target folder with a jar file. In this example, the name of jar file will be - spring-petclinic-2.7.0-SNAPSHOT.jar

Dockerfile

In the root of the folder create a file named as Dockerfile and copy the below content in it.

# Choose your Java image
FROM  openjdk:8-jdk-alpine

# Create volume for the Java jar build process
VOLUME  /tmp

# Copy the jar to the container
COPY  target/*.jar  app.jar

# Set your command to start the Java application
ENTRYPOINT  ["java","-jar","/app.jar"]

Build an image

Now run this command in the terminal :

docker build -t myorg/myapp .

This will create a docker image of the application.

Now run the following command to run the container :

docker run -p 8080:8080 myorg/myapp

It will take some time and this will be showing in your terminal, and your application is started now. Now go to localhost:8080 and check your application running from inside a container.