Converting JSON data to Java object

Question

I want to be able to access properties from a JSON string within my Java action method. The string is available by simply saying myJsonString = object.getJson(). Below is an example of what the string can look like:

{
    'title': 'ComputingandInformationsystems',
    'id': 1,
    'children': 'true',
    'groups': [{
        'title': 'LeveloneCIS',
        'id': 2,
        'children': 'true',
        'groups': [{
            'title': 'IntroToComputingandInternet',
            'id': 3,
            'children': 'false',
            'groups': []
        }]
    }]
}

In this string every JSON object contains an array of other JSON objects. The intention is to extract a list of IDs where any given object possessing a group property that contains other JSON objects. I looked at Google's Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

Answer 1

HashMap keyArrayList = new HashMap();
        Iterator itr = yourJson.keys();
        while (itr.hasNext())
        {
            String key =(String) itr.next();
            keyArrayList.put(key, yourJson.get(key).toString());
        }

Answer 2

What's wrong with the standard stuff?

JSONObject jsonObject = new JSONObject(someJsonString);
JSONArray jsonArray = jsonObject.getJSONArray("someJsonArray");
String value = jsonArray.optJSONObject(i).getString("someJsonValue");

Answer 3

Depending on the input JSON format(string/file) create a jSONString. Sample Message class object corresponding to JSON can be obtained as below:

Message msgFromJSON = new ObjectMapper().readValue(jSONString, Message.class);

Answer 4

If you use any kind of special maps with keys or values also of special maps, you will find it's not contemplated by the implementation of google.

Answer 5

Give boon a try:

https://github.com/RichardHightower/boon

It is wicked fast:

https://github.com/RichardHightower/json-parsers-benchmark

Don't take my word for it... check out the gatling benchmark.

https://github.com/gatling/json-parsers-benchmark

(Up to 4x is some cases, and out of the 100s of test. It also has a index overlay mode that is even faster. It is young but already has some users.)

It can parse JSON to Maps and Lists faster than any other lib can parse to a JSON DOM and that is without Index Overlay mode. With Boon Index Overlay mode, it is even faster.

It also has a very fast JSON lax mode and a PLIST parser mode. :) (and has a super low memory, direct from bytes mode with UTF-8 encoding on the fly).

It also has the fastest JSON to JavaBean mode too.

It is new, but if speed and simple API is what you are looking for, I don't think there is a faster or more minimalist API.

Answer 6

Or with Jackson:

String json = "...
ObjectMapper m = new ObjectMapper();
Set<Product> products = m.readValue(json, new TypeReference<Set<Product>>() {});