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

Question

This question already has answers here:

Convert JSONArray to String Array (18 answers)

Closed 6 years ago.

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[]) ?

• Smile: Does this answer your question? Convert JSONArray to String Array
• f1sh: The exception is trying to tell you something, did you read it?
• Itération 122442: @Smile No, as I want a String[] and not an ArrayList<String>. (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: @f1sh Yes. And I do not know how to solve this, thus the question.
• Mark Rotteveel: Did you read all the answers on that question. The second answer shows how to create a string array.

Answer 1

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;

• Itération 122442: I am working with jsonsimple. A JSONObject does not have the method getJSONObject :S