Essential Books

Check for the existence of fields on JSON

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Sometimes it’s useful to check if a field is present or absent on your JSON to avoid some JSONException on your code.

To achieve that, use the JSONObject#has(String) or the method, like on the following example:

Sample JSON 

{
   "name":"James"
}

Java code 

String jsonStr = " { \"name\":\"James\" }";
JSONObject json = new JSONObject(jsonStr);
// Check if the field "name" is present
String name, surname;

// This will be true, since the field "name" is present on our JSON.
if (json.has("name")) {
    name = json.getString("name");
}
else {
    name = "John";
}
// This will be false, since our JSON doesn't have the field "surname".
if (json.has("surname")) {
    surname = json.getString("surname");
}
else {
    surname = "Doe";
}

// Here name == "James" and surname == "Doe".
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JSON handling with org.json:
* JSON in Android with org.json
* Creating a simple JSON object
* Create a JSON String with null value.
* Parsing JSON with Gson
* Add JSONArray to JSONObject
* Parse simple JSON object
* Parsing a ListString with Gson
* Check for the existence of fields on JSON
* Create nested JSON object
* Parsing JSON to Generic Class Object with Gson
* Parsing JSON property to enum with Gson
* Using JsonReader to read JSON from a stream
* Working with null-string when parsing json
* Handling dynamic key for JSON response
* Parsing json array to generic class using Gson
* Custom JSON Deserializer using Gson
* JSON SerializationDeserialization with AutoValue and Gson
* Updating the elements in the JSON
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