Spring Boot Dockerfile error: unknown instruction: JAVA

Question

I have the following Dockerfile that I'm trying to use to containerize my Spring Boot application:

FROM openjdk:8-jdk-alpine as myservice

COPY build/libs/my-service.jar my-service.jar

HEALTHCHECK CMD curl --fail https://localhost:9200/healthCheck || exit 1

EXPOSE 443 9200

ENTRYPOINT [
    "java", \
    "-Dspring.config=.", \
    "-Dspring.profiles.active=local", \
    "-Dkeystore.file=mykey.p12, \
    "-jar", \
    "my-service.jar"
]

When I run:

docker build -t myorg/my-service .

I get:

Sending build context to Docker daemon   82.5MB
Error response from daemon: Dockerfile parse error line 10: unknown instruction: "JAVA",

What's going on here?

Answer 1

It's reading "java" as a separate Dockerfile instruction. You need to escape the first line of your entrypoint command after [ and on your last line before ] if you want them to be on separate lines:

ENTRYPOINT [ \
    ... \
]
    

Like this:

ENTRYPOINT [ \
    "java", \
    "-Dspring.config=.", \
    "-Dspring.profiles.active=local", \
    "-Dkeystore.file=mykey.p12, \
    "-jar", \
    "my-service.jar" \
]

I recommend using a linter to catch errors like this. hadolint is a good command-line linter and you can easily download Dockerfile linters for most IDEs.