[FIXED] How to read array of objects or empty array using groovy in jenkins file?

Issue

Unable to resolve the below error while trying to create a pipeline using a groovy script.

java.lang.ClassCastException: org.jenkinsci.plugins.workflow.steps.EchoStep.message expects class java.lang.String but received class net.sf.json.JSONArray

My script is as below

#!groovy
import groovy.json.*

pipeline {
    agent any

    stages {
       stage('Publish To Exchange') {
          steps {
             script{
                def apiUrl = "https://something.com/login"
                def payload = JsonOutput.toJson(["username":"username", "password":"password"])
                def response = sh (returnStdout: true, script: "curl -s --fail -H \"Content-Type: application/json\" -X POST ${apiUrl} -d '${payload}' ").trim()
        
                def parsedJson = readJSON text: response
                def token = parsedJson.access_token
        
                echo token
        
                def props = readJSON text: sh(returnStdout: true, script: "curl -s --fail -H \"authorization: Bearer $token\" https://something.com/assets?search=my-api")
        
                echo  props //error, output empty array or array of objects
              }
            }
         }
      }
  }

I get the error while printing props. I also tried the below but it failed too with the below error.

java.lang.ClassCastException: org.jenkinsci.plugins.workflow.steps.EchoStep.message expects class java.lang.String but received class java.util.ArrayList

....
def props = sh(returnStdout: true, script: "curl -s --fail -H \"authorization: Bearer $token\" https://something.com/assets?search=my-api")
def json = new JsonSlurper().parseText(props)
echo json

Any help is appreciated. Thanks

Solution

use echo (json as String) or println json

---

diff between println and echo:

println is a method from groovy Object class - it accepts any object as input parameter, converts it to a string if needed, and prints the result.

echo is one of the basic steps of jenkins pipeline and it requires string as input. so, before using it to print non-string values - you have to convert them to string.

Answered By - daggett
Answer Checked By - Timothy Miller (JavaFixing Admin)