Maven pipeline fails to find JDK - jenkins

Question

I have a problem running a simple Java Maven pipeline. The used maven command fails using the expected JDK for an unknown reason.
freshly installed Jenkins running from the docker image jenkinsci/blueocean:latest
configured Oracle JDK 9 and Maven 3.5.4 at the Jenkins Tools settings pane
Jenkinsfile content:
pipeline {
agent any
tools {
jdk 'java9'
maven 'Maven3.5'
}
stages {
stage ('Initialize') {
steps {
sh '''
echo "PATH = ${PATH}"
echo "M2_HOME = ${M2_HOME}"
echo "JAVA_HOME = ${JAVA_HOME}"
'''
}
}
stage ('Build') {
steps {
sh 'java -version'
sh 'mvn --version'
}
}
}
}
Output of the "Initialize" stage script
PATH = /var/jenkins_home/tools/hudson.model.JDK/java9/bin:/var/jenkins_home/tools/hudson.tasks.Maven_MavenInstallation/Maven3.5/bin:/var/jenkins_home/tools/hudson.model.JDK/java9/bin:/var/jenkins_home/tools/hudson.tasks.Maven_MavenInstallation/Maven3.5/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/lib/jvm/java-1.8-openjdk/jre/bin:/usr/lib/jvm/java-1.8-openjdk/bin
M2_HOME = /var/jenkins_home/tools/hudson.tasks.Maven_MavenInstallation/Maven3.5
JAVA_HOME = /var/jenkins_home/tools/hudson.model.JDK/java9
This looks valid to me. M2_HOME and JAVA_HOME point to the expected path of the Jenkins tools.
Output of the "Build" "java -version" script
+ java -version
openjdk version "1.8.0_191"
OpenJDK Runtime Environment (IcedTea 3.10.0) (Alpine 8.191.12-r0)
OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)
This seems to be the installed Java of the Jenkins docker host system
Failure output of the "Build" "mvn -version" script:
mvn --version
/var/jenkins_home/tools/hudson.tasks.Maven_MavenInstallation/Maven3.5/bin/mvn: exec: line 191: /var/jenkins_home/tools/hudson.model.JDK/java9/bin/java: not found
script returned exit code 127
If I bash into the Jenkins docker container, I find the java bin at the mentioned path.
Where is my mistake? Why can't Maven find the Java?
Is it a permission problem? Jenkins docker container uses a docker volume:
-v jenkins-data:/var/jenkins_home.
Best,
Lars

Answer 1

Not sure tools + docker in Jenkins Pipeline is working so good.
See: https://issues.jenkins-ci.org/browse/JENKINS-36159
Only way so far I've managed to get this to work was by mounting the docker node's tools directory into the docker slave.
e.g.
agent { docker
args '-v $HOME/tools:/var/lib/jenkins/tools'
stage { step {
sh "${MAVEN_HOME}/bin/mvn -version"
EDIT: Just found this too: https://issues.jenkins-ci.org/browse/JENKINS-48050

Answer 2

You don't need both tools. It is enough with Maven tool. It includes Java. Your pipeline should be:
pipeline {
agent any
tools {
maven 'Maven3.5'
}
stages {
stage ('Initialize') {
steps {
sh '''
echo "PATH = ${PATH}"
echo "M2_HOME = ${M2_HOME}"
echo "JAVA_HOME = ${JAVA_HOME}"
'''
}
}
stage ('Build') {
steps {
sh 'java -version'
sh 'mvn --version'
}
}
}
}
And you can delete Java Tool in Jenkins configuration tool.

Answer 3

This problem occurs when you're using an alpine based docker image for jenkins and your jdk is glibc based. You can solve this in two ways:
Use a jdk that is musl based. You can find them on adoptium by filtering out the OS as Alpine Linux.
Use a non-alpine based docker image.