如何使用GSON解析JSON，以获取未针对不良JSON进行解析的JSONObject？

Question

The question is that when I am parsing the following JSON using GSON library, I am getting GSON class in the form of POJO , where every key and value has a getter and setter.

See the example of such bad JSON below, as not parsed correctly by GSON library

Now that is not the format I require. Instead, I want a hashmap object in return (Library can return ArrayList then why not TreeHashMap ?) . For me, this part of JSON is not parsed by GSON as I desire.

My question is whether I should ask my back-end team to reformat the JSON as in second JSON below, or to try to use GSON library as is but extract that JSONObject programmatically from JSON where the keys are dynamic in nature, and it is uncertain whether there are a couple of such keys there or thousands of them in the JSON that is returned.

See the example of the good JSON format below, converted from the bad JSON I have provided as it can be easily parsed by GSON to the format I desire

For this, either I have to explain a rule to my back-end team:

RULE:

The keys should not be dynamic in nature. If in case the keys are dynamic, a list of searchable keys should also be defined in the same JSON or separate MODEL JSON that should be requested in a call before this JSON is parsed (in a separate Web-Service API response).

Example of bad JSON:

{"Grocery": [
      {
        "id": 2,
        "name": "Kirana Store",
        "parent_id": 1,
        "category_image": "",
        "category_type": "product",
        "position": 0,
        "front_status": 0,
        "slug_url": "daal-pulses",
        "created_at": "2016-06-27 06:44:59",
        "updated_at": "2018-02-13 04:55:33"
      },
      {
        "id": 3,
        "name": "Departmental Store",
        "parent_id": 1,
        "category_image": "",
        "category_type": "product",
        "position": 0,
        "front_status": 0,
        "slug_url": "dry-fruits",
        "created_at": "2016-06-27 06:45:12",
        "updated_at": "2018-02-13 04:56:01"
      }
    ]}

and there may be thousands of dynamic keys like " Grocery " say like " Stationary ", " Hosiery ", " Medicines ", or so... as categories of products. GSON will make getters for each such dynamic key.

Should be corrected and returned by web-service API as:

{

  "Products": [

    {

      "parent_category": "Grocery",

      "items": [

        {

          "id": 2,

          "name": "Kirana Store",

          "parent_id": 1,

          "category_image": "",

          "category_type": "product",

          "position": 0,

          "front_status": 0,

          "slug_url": "daal-pulses",

          "created_at": "2016-06-27 06:44:59",

          "updated_at": "2018-02-13 04:55:33"

        },

        {

          "id": 3,

          "name": "Departmental Store",

          "parent_id": 1,

          "category_image": "",

          "category_type": "product",

          "position": 0,

          "front_status": 0,

          "slug_url": "dry-fruits",

          "created_at": "2016-06-27 06:45:12",

          "updated_at": "2018-02-13 04:56:01"

        }

      ]

    }

  ]

}

Where there can be thousands of categories as Grocery as described above, and getters for such keys can not be computed at run time. But if these keys are converted to values, represented by a common key each, as in the correction above, then having a common getter for that key " parent_category " makes sense. Now, this is the JSON that GSON can parse to my desired output. But the thing is that our back end team do not co-operate to change anything, because there is a re-work here. If I switch to traditional parsing, there will be a huge re-work at my end as well.

OR I have to find out a way where I can extract the JSONObject from the JSON using GSON so that I can parse it manually.

Hence I need something to save time that will go in this re-work.

Answer 1

After getting JSONObject that is not parsed by GSON as desired:

Getting JSONObject from JSON where it is not parsable by GSON :

Use keySet() of JSONObject to get the keys from JSON , as Set collection. Iterating through the keys in the Set, I am obtaining corresponding values, in the current JSON section.

Please see the example:

Java Code Examples for org.json.JSONObject.keySet()

Now if GSON can not parse such kind of JSON formats, where it gives getters and setters for each key and if the developer has to parse JSON manually, then still there is a chance of saving time, using this solution. But till GSON make amendments as you suggest it should, you have to live with this solution.

What should I have done if I were in GSON development team?:

There should have been another kind of annotation where instead of getting getters and setters, one should be able to demand from the GSON library to return key-value pairs in the form of hash-map or array-list of POJO in the output. This at present is not there.

Happy Coding ;-)