Java can't find file while running in Docker container

Question

I reference an HTML file in my code, and access it with:

Path filePath1 = Path.of("./email.html");

When I run the project locally, the project works fine, and the file loads normally. However, when running the project in a Docker container, I get the following error:

java.nio.file.NoSuchFileException: ./email.html

Here is my Docker file for reference

FROM openjdk:11.0-jdk-slim as builder

VOLUME /tmp
COPY . .
RUN apt-get update && apt-get install -y dos2unix
RUN dos2unix gradlew
RUN ./gradlew build

# Phase 2 - Build container with runtime only to use .jar file within
FROM openjdk:11.0-jre-slim
WORKDIR /app
# Copy .jar file (aka, builder)
COPY --from=builder build/libs/*.jar app.jar
ENTRYPOINT ["java", "-Xmx300m",  "-Xss512k", "-jar", "app.jar"]
EXPOSE 8080

Thank you for the answers. So this is a Java project, so there is no index.html to add. I tried changing the work directory to /src, but it is still not picking it up

Is your file located at /app/email.html? You set the WORKDIR to /app in your Dockerfile, so any relative file references in your code should be relative to /app. — mpriscella
– mpriscella, Commented May 2, 2022 at 4:30
the file is in the root directory. I tried putting it in the src folder, and also just commenting out the WORKDIR line (so it stays at the root level), but neither worked — Yaxet
– Yaxet, Commented May 3, 2022 at 3:52

Dominik Lovetinsky · Accepted Answer · 2022-05-02 04:32:08Z

3

Docker has no access to the filesystem fromm the host OS. You need to put it in there as well:

COPY ./index.html index.html

answered May 2, 2022 at 4:32

Dominik Lovetinsky

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GeertPt · Accepted Answer · 2022-05-02 08:22:06Z

0

There's a couple of options:

Copy the index.html in the docker image (solution by ~dominik-lovetinsky)
Mount the directory with your index.html file as a volume in your docker instance.
Include the index.html as a resource in your app.jar, and access it as a classpath resource.

The last option: including resources as classpath resource, is the normal way webapps work, but I'm not sure if it works for you.

answered May 2, 2022 at 8:22

GeertPt

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