How to parse JSON in Java

The org.json library is easy to use.

Just remember (while casting or using methods like getJSONObject and getJSONArray) that in JSON notation

[ … ] represents an array, so the library will parse it to JSONArray
{ … } represents an object, so the library will parse it to JSONObject
Example code below:

import org.json.*;



String jsonString = ... ; //assign your JSON String here

JSONObject obj = new JSONObject(jsonString);

String pageName = obj.getJSONObject("pageInfo").getString("pageName");



JSONArray arr = obj.getJSONArray("posts"); // notice that `"posts": [...]`

for (int i = 0; i < arr.length(); i++)

{

    String post_id = arr.getJSONObject(i).getString("post_id");

    ......

}

You may find more examples from Parse JSON in Java

4 years ago

If one wants to create Java object from JSON and vice versa, use GSON or JACKSON third party jars etc.

//from object to JSON 

Gson gson = new Gson();

gson.toJson(yourObject);

// from JSON to object 

yourObject o = gson.fromJson(JSONString,yourObject.class);

But if one just want to parse a JSON string and get some values, (OR create a JSON string from scratch to send over wire) just use JaveEE jar which contains JsonReader, JsonArray, JsonObject etc. You may want to download the implementation of that spec like javax.json. With these two jars I am able to parse the json and use the values.
These APIs actually follow the DOM/SAX parsing model of XML.

Response response = request.get(); // REST call 

    JsonReader jsonReader = Json.createReader(new StringReader(response.readEntity(String.class)));

    JsonArray jsonArray = jsonReader.readArray();

    ListIterator l = jsonArray.listIterator();

    while ( l.hasNext() ) {

          JsonObject j = (JsonObject)l.next();

          JsonObject ciAttr = j.getJsonObject("ciAttributes");

4 years ago