Using simple json, transform a json object containing a json array into an array of strings (in java)

Question

As this question has been closed before actual answer for this specific problem has been found, it is here.

In java, I am using the simplejson library to handle json.

My json have this structure (truncated):

{

    "assembling-tags": {
        "list": [
            "G_StaticCushion_R",
            "G_CommutationPosition_R",
            "G_PlastificationPlasticisingDuration_R",
            "G_PlastificationScrewPositionAfter_R",
            "G_CommutationPressure_R",
            "G_DynamicCommutationDuration_R",
            "G_DynamicLockingToolDuration_R",
            "G_CycleTime_R",
            "CYCLE_TIME",
            "G_ClosureSecurityClosingToolDuration_R"
        ]
    },

I read the json data with the following code:

try (FileReader reader = new FileReader(
                "/home/hduser/eclipse-workspace/db-simulatiob/src/generator-config.json")) {

            JSONObject obj = (JSONObject) jsonParser.parse(reader);

And I am trying to convert the list json array into a string array, with the following:

String[] aTag = (String[]) ((JSONObject) obj.get("assembling-tags")).get("list");

But this throws the following exception:

Exception in thread "main" java.lang.ClassCastException: org.json.simple.JSONArray cannot be cast to [Ljava.lang.String;

How can I convert the json array into a string array (String[]) ?

Does this answer your question? [Convert JSONArray to String Array](https://stackoverflow.com/questions/15871309/convert-jsonarray-to-string-array) — Smile, Jan 06 '20 at 10:55
The exception is trying to tell you something, did you read it? — f1sh, Jan 06 '20 at 10:58
@Smile No, as I want a String[] and not an ArrayList. (WIll edit question for this detail). Also I am working with jsonsimple, so I have a JSON Object (see code), not a string. — Itération 122442, Jan 06 '20 at 12:22
@f1sh Yes. And I do not know how to solve this, thus the question. — Itération 122442, Jan 06 '20 at 12:22
Did you read **all** the answers on that question. The second answer shows how to create a string array. — Mark Rotteveel, Jan 06 '20 at 12:34
@MarkRotteveel Yes, and it uses `org.json.*;`, I am using `org.json.simple.*;`. These are not the same libraries. — Itération 122442, Jan 06 '20 at 12:47
As far as I know, the principle is the same. In any case, you cannot cast a `JSONObject` to a `String[]` like you're doing. — Mark Rotteveel, Jan 06 '20 at 12:57
@MarkRotteveel Posted answer here (https://stackoverflow.com/a/59612759/6213883) as it is a bit different. — Itération 122442, Jan 06 '20 at 13:12

score 0 · Answer 1 · edited Jan 06 '20 at 12:38

Use below code, Hopefully it will solved your problem:

String jstr = "{\r\n" + 
                "\r\n" + 
                "    \"assembling-tags\": {\r\n" + 
                "        \"list\": [\r\n" + 
                "            \"G_StaticCushion_R\",\r\n" + 
                "            \"G_CommutationPosition_R\",\r\n" + 
                "            \"G_PlastificationPlasticisingDuration_R\",\r\n" + 
                "            \"G_PlastificationScrewPositionAfter_R\",\r\n" + 
                "            \"G_CommutationPressure_R\",\r\n" + 
                "            \"G_DynamicCommutationDuration_R\",\r\n" + 
                "            \"G_DynamicLockingToolDuration_R\",\r\n" + 
                "            \"G_CycleTime_R\",\r\n" + 
                "            \"CYCLE_TIME\",\r\n" + 
                "            \"G_ClosureSecurityClosingToolDuration_R\"\r\n" + 
                "        ]\r\n" + 
                "    }}";

        JSONObject obj  = new JSONObject(jstr);
        JSONArray jarr = obj .getJSONObject("assembling-tags").getJSONArray("list");
        String[] aTag =new String[jarr.length()];
        for(int i=0; i<aTag.length; i++) {
            aTag[i]=jarr.optString(i);
        } // aTag is ready to use 

        // Here I just print the output
        for(int i=0; i<aTag.length; i++) {
            System.out.println("jsonArray to String array:"+aTag[i]); 
        }

Also import below:

import org.json.JSONArray;
import org.json.JSONObject;

I am working with jsonsimple. A `JSONObject` does not have the method `getJSONObject` :S — Itération 122442, Jan 06 '20 at 12:24

Using simple json, transform a json object containing a json array into an array of strings (in java)

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