Pass command line args to Java app (Spring Boot) running in Docker

Question

I'm trying to pass command line args to the main method of a Spring Boot app running in a Docker container. Running from the command line, I would do something like this:

 $ mvn spring-boot:run -Dspring-boot.run.arguments=--greeting=Hello,--recipient=World

The app needs to pick these args up and do some processing with them:

public static void main(String[] args) {
    Options options = new Options();

    Option greeting = new Option("-g", "greeting", true, "Greeting");
    greeting.setRequired(true);
    greeting.addOption(greeting);

    Option recipient = new Option("-r", "recipient", true, "Recipient");
    recipient.setRequired(true); 
    recipient.addOption(recipient);

    try {
        cmd = parser.parse(options, args);
    } catch (ParseException e) {
        System.out.println(e.getMessage());
        formatter.printHelp("utility-name", options);
        System.exit(1);
    }

    // Do some processing using these args ...

    // Run the Spring Boot app
    SpringApplication.run(SpringBootApp.class, args);
}

I have tried simply passing them in using the -e flag:

docker run -p 8080:8080 -d -e "greeting=Hello" -e "recipient=World" test-image

My Dockerfile looks like this:

FROM openjdk:8-jdk-alpine
VOLUME /tmp
COPY ./target/spring-boot-app-0.0.1-SNAPSHOT.jar app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

Since options (args) are required, I keep receiving an error message and the app exits.

Solution 1

You can provide all command line arguments just after name of your docker image in run command.

Example:

docker run -p 8080:8080 test-image --recipient="World"--greeting="Hello"

Solution 2

You can try to modify your ENTRYPOINT in your Dockerfile like that:

ENTRYPOINT exec java -jar -Dspring-boot.run.arguments=--greeting=Hello,--recipient=World

Or you can pass argument at run:

docker run -p 8080:8080 test-image --recipient="World"--greeting="Hello"

Comments

[miken]

Awesome. I haven't seen anything resembling starting the container this way while trying to figure this out. Thanks @Evgeniy Strepetov

[miken]

I tried something similar with ENTRYPOINT but the syntax was a little funky, but this makes total sense. Thanks @veben

[ddsultan]

Please note: passing system arguments only works if you have exec form entrypoint (e.g.: ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/a‌​pp.jar"]). Details are described here

[Paulo Merson]

Setting fixed values for the arguments in the ENTRYPOINT line in the Dockerfile does not make sense to me.