Jenkins "Invoke Maven 3" build step does not expose POM_* variables - maven

Question

I am using Jenkins as my CI server and Artifactory as my artifact repository. The Artifactory plugin works in free-style projects and can be used just by using Invoke Maven3 build step to both fetch the dependencies and deploy the artifacts. Furthermore, I have another build step for building a docker image and pushing it to my private docker registry using CloudBees Docker Build and Publish plugin.
The problem is that I want to use POM_* variables in CloudBees configurarion that should be exposed by Maven Plugin as mentioned here. But everytime I build the project, I got the following error:
ERROR: Unrecognized macro 'POM_VERSION' in '${POM_VERSION}'
org.jenkinsci.plugins.tokenmacro.MacroEvaluationException: Unrecognized macro 'POM_VERSION' in '${POM_VERSION}'
at org.jenkinsci.plugins.tokenmacro.TokenMacro.expand(TokenMacro.java:198)
at org.jenkinsci.plugins.tokenmacro.TokenMacro.expandAll(TokenMacro.java:233)
at org.jenkinsci.plugins.tokenmacro.TokenMacro.expandAll(TokenMacro.java:222)
at com.cloudbees.dockerpublish.DockerBuilder$Perform.expandAll(DockerBuilder.java:266)
at com.cloudbees.dockerpublish.DockerBuilder$Perform.getNameAndTag(DockerBuilder.java:277)
at com.cloudbees.dockerpublish.DockerBuilder$Perform.exec(DockerBuilder.java:247)
at com.cloudbees.dockerpublish.DockerBuilder$Perform.access$100(DockerBuilder.java:233)
at com.cloudbees.dockerpublish.DockerBuilder.perform(DockerBuilder.java:208)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:779)
at hudson.model.Build$BuildExecution.build(Build.java:205)
at hudson.model.Build$BuildExecution.doRun(Build.java:162)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:537)
at hudson.model.Run.execute(Run.java:1744)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:374)
Build step 'Docker Build and Publish' marked build as failure
I do not know what exactly is the reason of this problem. Maybe the Invoke Maven3 build step is causing this problem by not exposing env variables. Another source of this could be CloudBees Plugin that does not utilize env variables. Any ideas?

Answer 1

The build step you mention, in a freestyle project, is not part of the Maven plugin. The environment variable described is only set for native Maven projects. From another project type, I suppose you would need to do something like
POM_VERSION=$(mvn help:evaluate -Dexpression=project.version | fgrep -v '[INFO]')
at the start of a script which continued to go on to use that variable.
Exposing the variable to subsequent non-shell build steps, such as from the CloudBees Docker Build and Publish plugin, is another matter; there may be some plugin that can do it, but I am not sure what offhand. (EnvInject perhaps.) It may be simpler to switch to a workflow job, using the CloudBees Docker Workflow plugin to drive Docker operations (depending on what exactly you are using from the Artifactory plugin):
node {
stage 'build'
git '…'
sh 'mvn package'
stage 'package'
sh 'mvn help:evaluate -Dexpression=project.version | fgrep -v '[INFO]' > .version'
def version = readFile '.version'
def image = docker.build("my-image:${version}")
stage 'publish'
docker.withRegistry(…) {
image.push()
}
}
By the way, you can add a shell build step just running
env | sort
if you are curious to see what environment variables are available.

Answer 2

Based on #Jesse Glick answer, searching around a little and struggling a bit with jenkins, I ended up with the following solution that works like a charm.
1-Add an "Execute Shell" build step containing following commands:
echo POM_VERSION=$(mvn help:evaluate -Dexpression=project.version | fgrep -v '[INFO]') > pom_file
echo POM_ARTIFACTID=$(mvn help:evaluate -Dexpression=project.groupId | fgrep -v '[INFO]') >> pom_file
echo POM_GROUPID=$(mvn help:evaluate -Dexpression=project.artifactId | fgrep -v '[INFO]') >> pom_file
2-Add an "Inject environment variables" build step (from EnvInject plugin) and enter "pom_file" as "Properties File Path"
3-Add a "Docker Build and Publish" build step and use POM_VERSION, POM_ARTIFACTID, POM_GROUPID in its configuration as you wish.