This is a simple spring boot application with the basic details of docker implementation.

• Spring boot application source code.
• Docker file.

• Create a simple spring boot application.
• Create a docker file under parent directory.
• Paste the following code in the docker file.

FROM openjdk:11-jre
VOLUME /tmp
ADD target/springBootDocker-1.0.0.jar springBootDocker.jar
ENTRYPOINT ["java","-jar","/springBootDocker.jar"]

FROM openjdk:11-jre
Here we are creating a docker image of openJre 11. And it will act as the parent image of our application.

VOLUME /tmp
This line is for allocating a folder to install our application. Because when we are executing our application tomcat needs space to create a work folder.

ADD target/springBootDocker-1.0.0.jar springBootDocker.jar
By this line, we are just specifying the path of the executable jar file and assign it to the "springBootDocker.jar" named file.

ENTRYPOINT ["java","-jar","/springBootDocker.jar"]
Here we are mentioning the comment that used to run the jar file in through the cmd.

• Go to the spring boot application root directory open the cmd and create jar file using following command mvn clean install

  Docker Commands

• Execute the following docker command to create the docker image.
  docker build -t <imagename> .
  • Here "-t" is used for mention the tag of container.
  • Our docker file is present in the same directory where we are executing this command. That is why we mentioned a dot at last of to commend
• To list the created docker images please use the following command. And make sure that our docker image is in the list.
  docker image ls
• Now it is time to run the docker image. Use the following command to run the docker image.
  docker run -p8080:8080 <imagename>
  • Here java application will be running inside the docket container , so we need to expose the application running port to outside the container. "-p8080:8080" is the command which expose the port to outside the docket container.