Use JsonSlurperClassic instead.

Since Groovy 2.3 (note: Jenkins 2.7.1 uses Groovy 2.4.7) JsonSlurper returns LazyMap instead of HashMap. This makes new implementation of JsonSlurper not thread safe and not serializable. This makes it unusable outside of @NonDSL functions in pipeline DSL scripts.

However you can fall-back to groovy.json.JsonSlurperClassic which supports old behavior and could be safely used within pipeline scripts.

Example

import groovy.json.JsonSlurperClassic @NonCPSdef jsonParse(def json) {    new groovy.json.JsonSlurperClassic().parseText(json)}node('master') {    def config =  jsonParse(readFile("config.json"))    def db = config["database"]["address"]    ...}    

ps. You still will need to approve JsonSlurperClassic before it could be called.

I ran into this myself today and through some bruteforce I've figured out both how to resolve it and potentially why.

Probably best to start with the why:

Jenkins has a paradigm where all jobs can be interrupted, paused and resumable through server reboots. To achieve this the pipeline and its data must be fully serializable - IE it needs to be able to save the state of everything. Similarly, it needs to be able to serialize the state of global variables between nodes and sub-jobs in the build, which is what I think is happening for you and I and why it only occurs if you add that additional build step.

For whatever reason JSONObject's aren't serializable by default. I'm not a Java dev so I cannot say much more on the topic sadly. There are plenty of answers out there about how one may fix this properly though I do not know how applicable they are to Groovy and Jenkins. See this post for a little more info.

How you fix it:

If you know how, you can possibly make the JSONObject serializable somehow. Otherwise you can resolve it by ensuring no global variables are of that type.

Try unsetting your object var or wrapping it in a method so its scope isn't node global.

EDIT: As pointed out by @Sunvic in the comments, the below solution does not work as-is for JSON Arrays.

I dealt with this by using JsonSlurper and then creating a new HashMap from the lazy results. HashMap is Serializable.

I believe that this required whitelisting of both the new HashMap(Map) and the JsonSlurper.

@NonCPSdef parseJsonText(String jsonText) {  final slurper = new JsonSlurper()  return new HashMap<>(slurper.parseText(jsonText))}

Overall, I would recommend just using the Pipeline Utility Steps plugin, as it has a readJSON step that can support either files in the workspace or text.