Gson is unable to parse a json array string located in an json object AS a JsonArray

Question

Context :

I am trying to convert the following JSON into a JAVA POJO using gson

JSON :

    {
    "task": "findRecords",
    "foundRecords": "[1234567, 11234512]",
    "logs": "records found [1234567, 11234512]",
    "status": "success"
}

POJO Class :

public class JavaPojo {
  String task = null;
  JsonArray foundRecords = null;
  String logs = null;
  String status = null;
}

Conversion logic :

  JavaPojo pojo = gson.fromJson(jsonString, JavaPojo.class);

where jsonString is the string representation of the above mentioned json.

Problem :

The conversion logic fails with

com.google.gson.JsonSyntaxException: Expected a com.google.gson.JsonArray but was com.google.gson.JsonPrimitive

From what i understand gson is interpreting foundRecords 's value as purely string and is not parsing it into an Array.

Now to get around this i modified foundRecords from JsonArray to String . the conversion happened successfully.

Any clue how can i achieve the conversion while preserving the type of foundRecords as JsonArray ?

Note:

After converting foundRecords to String , i tried converting the string value of foundRecords to JsonArray using gson and it strangely worked.

//This works
//Map json to pojo
  JavaPojo pojo = gson.fromJson(jsonString, JavaPojo.class);
//Convert foundRecords into a JsonArray
JsonArray arr = gson.fromJson(pojo.getFoundRecords(), JsonArray.class);

So now i am confused, if gson can convert string type foundRecords into JsonArray then why couldn't it perform the conversion earlier ?

Answer 1

I understand the REST API response is bad and is violating the JSON syntax. Solution is to correct the REST API, but in my scenario unfotunately i cannot request for API correction so i wrote a util at my end to clean the jsonString .

Posting it here if it helps anyone :

  /**
   * @param malformedArrayKey
   *          - Name of the key in the JSON object that has a malformed array
   *          for e.g consider following JSON object having a bad formed array
   *          <pre>
   *      {
   *        "task": "findRecords",
   *        "foundRecords": "[1234567, 11234512]",
   *      }
   *          </pre>
   * @param jsonString
   *          - String representation of the JSON object containing the malformed array
   * @return - json string having well formed array against the key {@code malformedArrayKey} supplied
   *         <pre>
   *        {
   *        "task": "findRecords",
   *        "foundRecords": [1234567, 11234512]
   *        }
   *         </pre>
   */
  public static String formatMalformedArray(String malformedArrayKey, String jsonString) {
    JsonObject jsonObj = gson.fromJson(jsonString, JsonObject.class);
    // get the faulty key value
    String malformedArrayKeyValue = jsonObj.get(malformedArrayKey)
        .getAsString();
    // drop it
    jsonObj.remove(malformedArrayKey);
    // create a array out of the malformed array string
    JsonArray jsonArray = gson.fromJson(malformedArrayKeyValue, JsonArray.class);
    // add the array back to the object
    jsonObj.add(malformedArrayKey, jsonArray);
    // now convert it into a well formed json string
    return jsonObj.toString();
  }

The method is quite basic but it satisifes my use case.