Jenkins loads data from json file as choices of parameter does not work properly

Question

I am completely novice at Jenkins, this post Jenkins Plugin:Extended Choice Parameter from JSON file does work for me.

I want to load a list of versions from a json file, which name is input.json, and use this version list as choices of one parameter, named version_list. The input.json file is in my $WORKSPACE, it's content is :

{
    "versions":["V1","V2"]
}

The pipeline script is as follows:

pipeline {
agent any


    stages {
        
        stage("load json") {
            steps {
                echo "version_list = ${params.version_list}"
            }
        }
        stage("open_json") {
            steps {
                script {
                    def prop = readJSON file: "${env.WORKSPACE}/input.json"
                    def version_list = prop.versions
    
                    println version_list.join(',')
                }
            }
        }
    }
}

The parameter version_list is setted as follows:

• Extended Choice Paramter

• name: versioin_list

• Parameter Type: Check Boxes

• Choose Source for Value: Groovy Script, and it's content is:

def prop = readJSON file: "${env.WORKSPACE}/input.json"
def version_list = prop.versions
return version_list.join(',')

When I build this job, there is nothing to choice for parameter version_list, but the output shows it can read data from input.json, this is one output:

Started by user admin
[Pipeline] Start of Pipeline
[Pipeline] node
Running on Jenkins in /home/hdl/.jenkins/workspace/json_as_parameter
[Pipeline] {
[Pipeline] stage
[Pipeline] { (load json)
[Pipeline] echo
version_list = null
[Pipeline] }
[Pipeline] // stage
[Pipeline] stage
[Pipeline] { (open_json)
[Pipeline] script
[Pipeline] {
[Pipeline] readJSON
[Pipeline] echo
"V1","V2"
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
Finished: SUCCESS

The load json stage can not get the value of ${params.version_list} but the open_json stage can load json properly.

If is replace groovy script of versison_list simpley as follows:

def version_list = ["V1","V2"]
return version_list.join(',')

It works well.

I don't know why. Any help, thanks!

Answer 1

It looks like there might be a small issue with how the Extended Choice Parameter is set up.

Try this:

pipeline {
    agent any

    parameters {
        extendedChoice(
            name: 'version_list',
            type: 'PT_CHECKBOX',
            groovyScript: '''
                import groovy.json.JsonSlurper

                def jsonFile = new File("${WORKSPACE}/input.json")
                def jsonContent = new JsonSlurper().parseText(jsonFile.text)
                return jsonContent.versions
            '''
        )
    }

    stages {
        stage("load json") {
            steps {
                echo "version_list = ${params.version_list}"
            }
        }
        stage("open_json") {
            steps {
                script {
                    def prop = readJSON file: "${env.WORKSPACE}/input.json"
                    def version_list = prop.versions

                    println version_list.join(',')
                }
            }
        }
    }
}