DockerFile to run a java program

Question

Hi I\'m new to Docker and trying out to write a new image from the scratch. I am writing this dockerFile to compile and run a simple java program available in the same directory

Answer 1

Another way...

1. you have to use "java:8" as base image or install jdk on "ubuntu" image.

2. build the image

   docker build -t imagename .
   

3. run it(mounting Helloworld.java to container)

   docker run -it -v ~/system-path:/javafolder imagename
   

type these commands to execute inside container-

cd javafolder

javac HelloWorld.java

java HelloWorld

Answer 2

Explanation

From the Dockerfile reference.

There can only be one CMD instruction in a Dockerfile. If you list more than one CMD then only the last CMD will take effect.

That is why the javac command is not executed and starting your container results in no such file or directory was found.

CMD and ENTRYPOINT are used for the tasks that shall be started once you execute the container (entrypoint level).

The main purpose of a CMD is to provide defaults for an executing container.

That applies to the line CMD java HelloWorld, but not to CMD javac HelloWorld.java which is more of a build step. That is what RUN is for.

Solution

Change the second line to RUN javac HelloWorld.java.

FROM scratch
RUN javac HelloWorld.java
CMD java HelloWorld

The resulting committed image [from line two] will be used for the next step in the Dockerfile.

Update

As Diyoda pointed out, make sure that the FROM image supplies java.

Answer 3

Here I am writing all commands and code that need to execute in order to run a hello world program on docker container without any build tool like gradle or maven.

devopsrider@del1-lhp-n02552:~ sudo su
root@del1-lhp-n02552:~# mkdir devopsrider
root@del1-lhp-n02552:~# cd devopsrider
root@del1-lhp-n02552:~/devopsrider# vi Test.java

public class Test{
        public static void main(String args[]){
                System.out.println("Hello World");

        }
}

root@del1-lhp-n02552:~# javac Test.java
root@del1-lhp-n02552:~/devopsrider# ls
Test.class  Test.java

root@del1-lhp-n02552:~/devopsrider# vi manifest.txt
Manifest-Version: 1.2
Main-Class: Test

root@del1-lhp-n02552:~/devopsrider# jar cvfm Test.jar manifest.txt Test.class
added manifest
adding: Test.class(in = 413) (out= 287)(deflated 30%)

root@del1-lhp-n02552:~/devopsrider# ls
manifest.txt  Test.class  Test.jar  Test.java

root@del1-lhp-n02552:~# vi Dockerfile
FROM openjdk:8
ADD Test.jar Test.jar
ENTRYPOINT ["java", "-jar", "Test.jar"]

root@del1-lhp-n02552:~/devopsrider# docker build -f Dockerfile -t hello-world-image .

Sending build context to Docker daemon  6.656kB
Step 1/3 : FROM openjdk:8
8: Pulling from library/openjdk
Digest: sha256:c168e211f317cc5db38b19fe62641316dbc1e60e5b53ad45ee440ba8152c20b9
Status: Downloaded newer image for openjdk:8
 ---> 57c2c2d2643d
Step 2/3 : ADD Test.jar Test.jar
 ---> b7d512e51b60
Step 3/3 : ENTRYPOINT ["java", "-jar", "Test.jar"]
 ---> Running in 07c871318e8a
Removing intermediate container 07c871318e8a
 ---> 24b1a0acd314
Successfully built 24b1a0acd314
Successfully tagged hello-world-image:latest

root@del1-lhp-n02552:~/devopsrider# docker run hello-world-image
Hello World

For complete tutorial to run java Hello World program on docker container visit http://www.devopsrider.com/2019/11/19/hello-world-java-program-on-docker-container/

Answer 4

You can either use CMD or ENTRYPOINT.

Sample :

CMD ["sh", "-c", "java -jar Service.jar"]

Answer 5

FROM java:8

WORKDIR /

ADD HelloWorld.java HelloWorld.java

CMD javac HelloWorld.java

ADD HelloWorld.class HelloWorld.class

CMD java Test

Update the above details in your Dockerfile the rebuild the docker image and run.

Answer 6

Try to follow this, i have mentioned all the steps to be followed below.

Step 1. Create a java file HelloWorld.java

public class HelloWorld {

  public static void main(String[] args){

    System.out.println("Hello World! ");

  }

Step 1.1 Generate class file Ex: javac HelloWorld.java

Step 2. Create manifest.txt file

Manifest-Version: 1.0
Main-Class: HelloWorld

Step 3. Create jar file Ex: jar cfm HelloWorld.jar manifest.txt HelloWorld.class

Step 4. Create a file with name Dockerfile (no extension)

FROM java:7

WORKDIR /

ADD HelloWorld.jar HelloWorld.jar

EXPOSE 8080

CMD java -jar HelloWorld.jar

Step 5. Come out of the current directory For exampe: From C:/custom-docker/java-docker to C:/custom-docker and run this cmd docker build -t java-docker (use the folder name, here java-docker)

Note: Run the command prompt as administrator for windows or prefix sudo in all commands for linux

Step 6. Skipping (push and pull) - Optional

Step 7. Run this cmd docker images and find the latest Image ID

Example:

REPOSITORY | TAG | IMAGE ID | CREATED SIZE < none > | < none > | 58df7fdecdeb | 3 minutes ago

Step 8. Finally run this cmd docker run 58df7fdecdeb, and you could see output as

"Hello World"

PS. Thanks Julia Bondarchuk

-- Happy coding :)