jenkins pipeline script to deal module in subdirectory - jenkins

Question

I have a git url maven project which I want to only deal one of its submodule.
I write in pipeline script :
...
stage("mvn build") {
steps {
script {
sh "mvn package -DskipTests=true"
}
}
}
error arise: The goal you specified requires a project to execute but there is no POM in this directory (/xx/jenkins/workspace/biz-commons_deploy). so I add command :
sh "cd cmiot-services/comm" # subdir of biz-commons_deploy
def PWD = pwd();
echo "##=${PWD} "
sh "mvn package -DskipTests=true"
not work, print ##=/root/.jenkins/workspace/biz-commons_deploy, the error is the same as before .
how can I solve this problem and why the echo and error use different user space?
I make it using sh "mvn -f cmiot-services/comm/pom.xml package -DskipTests=true",still not know where this two user path come from and why sh cd not work.

Answer 1

steps {
sh '''
# list items in current directory to see where is your pom.xml
ls -l
# run job by comment out following two lines, if you don't know the
# relative path of folder where pom.xml insides exactly
cd <folder where pom.xml insides>
mvn package -DskipTests=true
'''
}

Answer 2

As Yong answered, every sh steps are independent, imagine Jenkins is opening a new ssh connection on your slave each time.
For your script, instead of a workaround with sh, why not using build in dir step ?
Something like this should do it :
stage("mvn build") {
steps {
script {
dir('cmiot-services/comm') {
sh "mvn package -DskipTests=true"
}
}
}
}

Answer 3

when you are executing Jenkins Pipline, the current directory is the Jenkins workspace directory.
You can add a step to clone the repo that your code is in (granted that the environment you are running the Jenkins instance is able to connect to your repo and clone).
You can then navigate into the directory that has the pom.xml. And finally execute the maven command.
...
stage("Clone Repo") {
steps {
script {
sh "git clone ssh://git#bitbucket.org:repo/app.git"
}
}
}
stage("mvn build") {
steps {
script {
sh "cd app/"
sh "pwd"
sh "mvn package -DskipTests=true"
}
}
}