Java - How to Parse empty Nested Json Array

Question

I am trying to Parse below JSON data to String in Java using (GSON) Library, I am able to parse all JSON fields data except one of the JSON Array. I want to check if it's null/empty then in String variable store null value, if it's not then store the original value.

Input JSON Data:

{
    "expand": "schema,names",
    "startAt": 0,
    "maxResults": 50,
    "total": 37875,
     "issues": [
            {
                "id": "1190",
                "key": "GDS-81",
                "fields": {
                    "issuetype": {
                        "id": "2170",
                        "name": "Service Request with Approvals",
                        "subtask": false
                    },
                    "customfield_29805": {
                        "id": "26",
                        "name": "Issue - First Response",
                        "completedCycles": []
                    }
                }
            }
        ]
     }

Code that I have done so far,

JsonObject object = (JsonObject) new JsonParser().parse(jsonResponse);              
JsonArray issuesArray = object.getAsJsonArray("issues");
for(int i=0; i<issuesArray.size(); i++) {
    JsonObject currentissues = (JsonObject) issuesArray.get(i); 
    String Issue_Id = (String) currentissues.get("id").toString().replace("\"", "");
    String Issue_Key =  (String) currentissues.get("key").toString().replace("\"", ""); 
    String Issue_Type = (String) currentissues.get("fields").getAsJsonObject().get("issuetype").getAsJsonObject().get("name").getAsString();
    JsonObject customfield = (JsonObject) currentissues.get("fields").getAsJsonObject().get("customfield_29805");
    JsonArray completedCyclesArray= customfield.getAsJsonArray("completedCycles");
    String Issue_FirstResponseStartTime = (completedCyclesArray.size() > 0) ? completedCyclesArray.getAsString() : "NULL";
}

However when I execute code I get below error on line :JsonObject customfield

java.lang.ClassCastException: com.google.gson.JsonNull cannot be cast to com.google.gson.JsonObject

[![UpdatedCode StackTrace][1]][1] [1]: https://i.sstatic.net/2wY0S.jpg

Answer 1

1. you dont need to explicitly , cast JsonElement to JsonObject instead use getAsJsonArray , Once you get your array, you can iterate through all the elements of it.

2. You also need to handle null check for completedCyclesArray before checking its siz else it will give you the NPE , I have fixed that as well. Please find the modified working code as below

    JsonParser parser = new JsonParser();
    JsonArray array = parser.parse(jsonResponse).getAsJsonArray();
    for(JsonElement e : array) {
        JsonObject currentissues = (JsonObject) e;
        String Issue_Id = (String) currentissues.get("id").toString().replace("\"", "");
        String Issue_Key =  (String) currentissues.get("key").toString().replace("\"", "");
        String Issue_Type = (String) currentissues.get("fields").getAsJsonObject().get("issuetype").getAsJsonObject().get("name").getAsString();
        JsonObject customfield = (JsonObject) currentissues.get("fields").getAsJsonObject().get("customfield_29805");
        JsonArray completedCyclesArray= customfield.getAsJsonArray("completedCycles");
        String Issue_FirstResponseStartTime = (null != completedCyclesArray && completedCyclesArray.size() > 0) ? completedCyclesArray.getAsString() : "NULL";
    }
   

   }

Please find my working solution for the updated json request(which not an array but nested json request)

JsonObject object = (JsonObject) new JsonParser().parse(jsonResponse);
JsonArray issuesArray = object.getAsJsonArray("issues");
String expand = object.get("expand").toString();
String startAt = object.get("startAt").toString();
String maxResults = object.get("maxResults").toString();
String total = object.get("total").toString();
System.out.println(String.format("expand %s , startAt %s, maxResults %s, total %s", expand, startAt, maxResults, total));
IntStream.range(0, issuesArray.size()).mapToObj(i -> (JsonObject) issuesArray.get(i)).forEach(currentissues -> {
    String Issue_Id = (String) currentissues.get("id").toString().replace("\"", "");
    String Issue_Key = (String) currentissues.get("key").toString().replace("\"", "");
    String Issue_Type = (String) currentissues.get("fields").getAsJsonObject().get("issuetype").getAsJsonObject().get("name").getAsString();
    JsonObject customfield = (JsonObject) currentissues.get("fields").getAsJsonObject().get("customfield_29805");
    JsonArray completedCyclesArray = customfield.getAsJsonArray("completedCycles");
    String Issue_FirstResponseStartTime = (completedCyclesArray.size() > 0) ? completedCyclesArray.toString() : "NULL";
    System.out.println(String.format("Issue_Id %s , Issue_Key %s, Issue_Type %s, Issue_FirstResponseStartTime %s", Issue_Id, Issue_Key, Issue_Type, Issue_FirstResponseStartTime));
});

and this is the output I got :

expand "schema,names" , startAt 0, maxResults 50, total 37875 Issue_Id 1190 , Issue_Key GDS-81, Issue_Type Service Request with Approvals, Issue_FirstResponseStartTime NULL

Please see my complete working code here complete code

for both the secnarios

Empty completedCycles

{
    "expand": "schema,names",
    "startAt": 0,
    "maxResults": 50,
    "total": 37875,
     "issues": [
            {
                "id": "1190",
                "key": "GDS-81",
                "fields": {
                    "issuetype": {
                        "id": "2170",
                        "name": "Service Request with Approvals",
                        "subtask": false
                    },
                    "customfield_29805": {
                        "id": "26",
                        "name": "Issue - First Response",
                        "completedCycles": []
                    }
                }
            }
        ]
     }

Non Empty completedCycles

{
"expand": "schema,names",
"startAt": 0,
"maxResults": 50,
"total": 37875,
 "issues": [
        {
            "id": "1190",
            "key": "GDS-81",
            "fields": {
                "issuetype": {
                    "id": "2170",
                    "name": "Service Request with Approvals",
                    "subtask": false
                },
                "customfield_29805": {
                    "id": "26",
                    "name": "Issue - First Response",
                      "completedCycles": [{"name":"abc"},{"name": "xyz"}]
                }
            }
        }
    ]
 }

Answer 2

Try adding getAsJsonObject() at the end of that statement.