Problem using mvn at building time

[doublebyte1]

I have the following use case:
1 - In the Dockerfile I build a mvn project and generate some jars
2 - then I go and build another project which uses the previous jars as dependencies

with the /root/.m2 volume, I find that the dependency jars (build on step 1), are gone, so I cannot successfully build the second project. This is maybe because the Dockerfile has layers, and the repository is not persisted in the second layer?

I already tried the approach that you advise in the README (using the settings.xml, as persisted repository), but I think this approach is designed to persist the repositories after the build of the Dockerfile , on runtime. I can see this image is designed to use maven on runtime, but what would be the correct way to use it also during building time?

[carlossg]

Nothing in /root/.m2 is persisted in the image, you would need to put the jars somewhere else

[doublebyte1]

Thanks for the quick reply. Based on what you said, this is what worked for me (maybe it can help others):

As the repository defined on settings.xml is only available on runtime, I have set it explicitly during my builds. Building the first project:

RUN mvn install -DskipTests -Drelax -gs /usr/share/maven/ref/settings-docker.xml

This has left the jars on /usr/share/maven/ref/repository, according to what is defined in settings.xml. Then I built the second project with the same flag:

RUN mvn install -DskipTests -Drelax -gs /usr/share/maven/ref/settings-docker.xml

And it found the dependencies on /usr/share/maven/ref/repository

[MrSleazy]

Hi @doublebyte1, @carlossg. Thanks for both of your answers.

I am actually having a similar issue. How did you customize the contents of setting-docker.xml inside of your image?

I currently need to set up a proxy for maven so I am trying to set up the build on a CI with the following image (https://github.com/alirizasaral/Maven-with-Proxy). This works fine, but I have the issue that maven downloads all the dependencies from scratch without caching them inside the repository every time I run a build on the CI.

Should I not be using an image based on alpine to get the maven repository to work correctly, or am I missing something more fundamental?

[cedricwalter]

@KevinSilvaQuintana

Add in your Dockerfile
COPY settings-docker.xml /usr/share/maven/ref/
in your docker directory, create a new file settings-docker.xml with content

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
  | xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  | xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
  | https://maven.apache.org/xsd/settings-1.0.0.xsd">
  | <localRepository>/usr/share/maven/ref/repository</localRepository>
  | </settings>

use in all mvn command
RUN mvn install -DskipTests -Drelax -gs /usr/share/maven/ref/settings-docker.xml

run again a build with no-cache to avoid to reuse some step that were not creating dependency jar in new repository folder
sudo docker build --no-cache <yourdockerdirectory>

[MrSleazy]

Hi @cedricwalter ,

I actually ended up finding a solution which I have outlined in this post:
https://stackoverflow.com/questions/33430487/how-to-use-gitlab-ci-to-build-a-java-maven-project

However, between that and your solution, I am not sure which is more 'clean'. Your approach is very simple and straight forward. However, I think that being able to centralize everything in the CI build file will allow for a more generic re-use for future projects. I'll give it a try though. 👍

[carlossg]

.m2 is no longer a volume