Jenkins Pipeline：根据参数设置环境变量

Question

I'm trying to set an environment variable in a Jenkins pipeline job based on a parameter passed into the job; this way I can use the environment variable in every stage of the pipeline that requires it. I tried using a switch statement in the environment block:

parameters {
    choice(name: 'ENVIRONMENT', choices: 'dev\nst\nprod', description: 'Environment')
}
environment {
  script {
    switch(env.ENVIRONMENT) {
      case 'dev':
        BRANCH = master
        break
      case 'st':
        BRANCH = 2020Q1
        break 
      case 'prod':
        BRANCH = 2019Q4
        break        
    }
  }
}

However this didn't work, the job tried to evaluate all the lines before the equals sign as the KEY name:

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 9: "script {
    switch(env.ENVIRONMENT) {
      case 'dev':
        BRANCH" is not a valid identifier and cannot be used for an environment variable. Identifiers must start with a letter or underscore and can contain only letters, numbers or underscores. @ line 9, column 7.
     script {

How do I get this to work?

Answer 1

There are few ways to achieve this. here is a one of them:

parameters {
   choice(name: 'ENVIRONMENT', choices: 'dev\nst\nprod', description: 'Environment')
}

stages(){
  stage("some stage"){
    steps {
        script{
            switch(env.ENVIRONMENT) {
              case 'dev':
                env.BRANCH = "master"
                break
              case 'st':
                env.BRANCH = "2020Q1"
                break 
              case 'prod':
                env.BRANCH = "2019Q4"
                break        
            }
            withEnv(["BRANCH=${env.BRANCH}"]) {
                ...................................
                ...................................
                ...................................

           }
        }
     }
   }
}