Docker Java Application failing at obtaining input from console

Question

I am trying to create a docker image for my java application. At startup this application needs to be given a password (currently via console).

I tried several methods of obtaining input however they have all failed. Is this a limitation of docker and if so is there a workaround?

For this snippet:

Console console = System.console();
if(console == null){
    System.out.println("console is null!!");
} else {
    System.out.println("Input password: ");
    char[] password = console.readPassword("Pass: ");
}

System.console() is returning null.

For this snippet:

    System.out.println("Creating InputStreamReader");
    InputStreamReader s = new InputStreamReader(System.in);
    System.out.println("Creating BufferedReader");
    BufferedReader r = new BufferedReader(s);
    System.out.println("Input password: ");
    String password = r.readLine();
    System.out.println("Password: "+password);

the input is automatically skipped, (resulting in the String password to be null) with the program continuing execution as if there was no input requested. (password is null)

For this snippet:

Scanner s = new Scanner(System.in);
System.out.println("Input password: ");
String password = s.next();

I get

Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Scanner.java:907)
    at java.util.Scanner.next(Scanner.java:1416)
    at com.docker.test.DockerTest.testScanner(DockerTest.java:49)
    etc...

I am running the program from within my image using docker run test/plaintest1

my dockerfile is as follows

FROM centos
RUN yum install -y java-1.7.0-openjdk
ADD DockerTest.jar /opt/ssm
ENTRYPOINT ["java","-jar","/opt/ssm/DockerTest.jar"]
CMD [""]

Civic

Can you detail how you're running your container ? – Wernick

docker run <imagename> <any optional parameters> as stated above. It hence runs java -jar on the jar which contains that code in the main – Civic

Answer 1

Solved it.

By running the command using the -i and -t parameters you can be allowed to enter the password. using all 3 methods.

so basically docker run -i -t <imagename> <params>

Civic

According to docker documentation, it says : -- interactive, -i Keep STDIN open even if not attached --tty , -t Allocate a pseudo-TTYThanks, it was very useful. Thanks, it was quite useful. – Kilter

Answer 2

I was struggling with this yesterday for most of the day. The problem seemed to have been a broken base image supplied by the official CentOS repo. If you look on your base image you will notice that /opt/java exists on the base image. That's the clue that you have the broken image. Simply pull the latest image with "docker pull centos" and you'll be back in action. They must have fixed it sometime last night. You'll notice the hash of the image has changed even though it shows that the image was uploaded 2 weeks ago. Someone is trying to hide their tracks! Haha. Your Dockerfile is fine.

Regards Wynand

Cloudcapped

oops, seems like I didn't read your question correctly - ignore my answer – Cloudcapped