gitlab CI/CD with maven doesn't setup environment variables in application.properties

Question

I am trying to build CI/CD pipeline with maven. Problem that I meet is that in application.properties I set variables like that:

database.MongoPass=${MONGO_PASS}
database.Secret=${SECRET}
database.connectionString=${ATLAS_STRING}
spring.data.mongodb.uri=${ATLAS_STRING}

and I cannot setup them it gitlab. Every time if gitlab will build package all time I cannot run it because connection string is wrong I get error: "The connection string is invalid. Connection strings must start with either 'mongodb://' or 'mongodb+srv://"

here example of variable that I set up in gitlab CI/CD settings

and here code that I tried run in gitlab CI/CD echo works correct and show correct variable value each mvn script I tried didn't work

 script:
    - echo $SECRET
    - echo $MONGO_PASS
    - echo $ATLAS_STRING
    - mvn install -B #  (I hope that application properties automatically get variables from gitlab env) 
    - mvn -DSECRET=$SECRET -DMONGO_PASS=$MONGO_PASS -DATLAS_STRING=$ATLAS_STRING clean install -B #  (I found this solution on stack) 
    - mvn -Dspring-boot.run.arguments=--database.Secret=$SECRET,--database.MongoPass=$MONGO_PASS,--spring.data.mongodb.uri=$ATLAS_STRING clean install -B #  (if I change here env variables for normal string it wont't build on gitlab) 

I don't have idea what I should do with that I don't want have variables saved in my repo and don't have idea what toDo with that. Could someone give me advice ? mvn script builds jar file in artifacts after each run I download it and run to test it with command

java -jar filename.jar

Update: I made small investigation and make class to test variables after spring startup:

  @PostConstruct
    public void test() {
        log.info("VARIABLES TEST");
        log.info("properties.getSecret(): {}", properties.getSecret());
        log.info("properties.getConnectionString(): {}", properties.getConnectionString());
        log.info("properties.getMongoPass(): {}", properties.getMongoPass());
    }

and variables are all time not set:

properties.getSecret(): ${SECRET}
properties.getConnectionString(): ${ATLAS_STRING}
properties.getMongoPass(): ${MONGO_PASS}

gitlab-ci.yml:

image: maven:3.8.1-jdk-11

build_artifact:
  stage: build
  script:
    - export
#    - mvn install -B -P no-tests
    - mvn -DSECRET=$SECRET -DMONGO_PASS=$MONGO_PASS -DATLAS_STRING=$ATLAS_STRING clean install -B -P no-tests #  (I found this solution on stack)
#    - mvn -Dspring-boot.run.arguments=--database.Secret=$SECRET,--database.MongoPass=$MONGO_PASS,--spring.data.mongodb.uri=$ATLAS_STRING clean install -B -P no-tests #  (if I change here env variables for normal string it wont't build on gitlab)
  artifacts:
    paths:
      - target/*.jar
    expire_in: 10 minutes

Example pipeline result:

Running with gitlab-runner 14.4.0-rc1 (bc99a056)
  on docker-auto-scale ed2dce3a
Preparing the "docker+machine" executor
00:23
Using Docker executor with image maven:3.8.1-jdk-11 ...
Pulling docker image maven:3.8.1-jdk-11 ...
Using docker image sha256:5b508b1fe19e290255c9e077a1c7af028a576cabb70eab4abdfee574599f729f for maven:3.8.1-jdk-11 with digest maven@sha256:aaf506d47cd2ec8f62fc1ff74065eda5614738e8ea61bad9b32da0360b9498cd ...
Preparing environment
00:01
Running on runner-ed2dce3a-project-16772800-concurrent-0 via runner-ed2dce3a-srm-1634103033-dfd4e8e6...
Getting source from Git repository
00:03
$ eval "$CI_PRE_CLONE_SCRIPT"
Fetching changes with git depth set to 50...
Initialized empty Git repository in /builds/**/***/.git/
Created fresh repository.
Checking out 60bf3869 as feature/branch
Skipping Git submodules setup
Executing "step_script" stage of the job script
$ mvn -DSECRET=$SECRET -DMONGO_PASS=$MONGO_PASS -DATLAS_STRING=$ATLAS_STRING clean install -B -P no-tests
***
Downloading all dependencies 
***
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  01:00 min
[INFO] Finished at: 2021-10-13T05:34:25Z
[INFO] ------------------------------------------------------------------------
Uploading artifacts for successful job
00:07
Uploading artifacts...
target/*.jar: found 1 matching files and directories 
Uploading artifacts as "archive" to coordinator... ok  id=1674250996 responseStatus=201 Created token=z2qnoeL8
Cleaning up project directory and file based variables
00:00
Job succeeded

Answer 1

Educated guess: you haven't enabled maven filtering for your application.properties property file.

Without filtering, those placeholders won't be replaced.

So have something like this in your pom file:

<project>
  ...
  <build>
    ...
    <resources>
      <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
      </resource>
      ...
    </resources>
    ...
  </build>
  ...
</project>

Answer 2

Try the following steps and make sure that each one is working properly:

1. Check whether your branch is protected or not. If it is not protected, you won't be able to access to defined environment variables.

2. Check whether the environment variables set properly or not using export command:

    script: - export # - <other commands>

3. Set filtering to true in your POM file.

4. Change application.properties to the following:

    database.MongoPass=$MONGO_PASS$ database.Secret=$SECRET$ database.connectionString=$ATLAS_STRING$ spring.data.mongodb.uri=$ATLAS_STRING$