Parsing JSON array in Java

Question

I'm currently parsing a JSON file to my Java Program and I ecounter a problem. I get a JSON array that can look like this for example:

[
 {
 "itemType": "magazineArticle",
 "creators": [
 {
 "firstName": "J. Antonio",
 "lastName": "Garcia-Macias",
 "creatorType": "author"
 },
 {
 "firstName": "Jorge",
 "lastName": "Alvarez-Lozano",
 "creatorType": "author"
 },
 {
 "firstName": "Paul",
 "lastName": "Estrada-Martinez",
 "creatorType": "author"
 },
 {
 "firstName": "Edgardo",
 "lastName": "Aviles-Lopez",
 "creatorType": "author"
 }
 ],
 "notes": [],
 "tags": [],
 "title": "Browsing the Internet of Things with Sentient Visors",
 "publicationTitle": "Computer",
 "volume": "44",
 "issue": "5",
 "ISSN": "0018-9162",
 "date": "2011",
 "pages": "46-52",
 "abstractNote": "Unlike the traditional Internet, the emerging Internet of Things constitutes a mix of virtual and physical entities. A proposed IoT browser enables the exploration of augmented spaces by identifying smart objects, discovering any services they might provide, and interacting with them.",
 "extra": "CICESE Research Center, Mexico; CICESE Research Center, Mexico; CICESE Research Center, Mexico; CICESE Research Center, Mexico",
 "libraryCatalog": "IEEE Computer Society"
 }
]

The problem is I have to do a check each time I parse if the field called "extra" is in the array, since it's not included every time i parse. So how do I do that check to see if the field "extra" exists?

• WeMakeSoftware: can't you use JSON parsing frameworks? Do you have to do it by hand?
• anderssinho: I have to do it by hand.
• user3460409: Can you use Jackson or JsonSimple ?
• WeMakeSoftware: show us your parsing code
• anderssinho: Would prefer if I just could do a Simple check in my javaprogram actually. Like when I get the abstract field in my program I do: String abstracts = obj.getString("abstractNote"); And I would like to do is just to make an check when I try to get the field if the field actually exists.

Answer 1

Without framework, you can use JSONObject and JSONArray from org.json.*. Here is an example (not tested). It will allows you to check if the extra key is present

String jsonAsString = "/*Your json as a String*/";
JsonArray jsonArray = new JSONArray(jsonAsString);
for(int i=0; i<jsonArray.length(); i++) {
 JSONObject jsonObject = jsonArray.getJSONObject(i);
 //Get values from your jsonObject
 jsonObject.has("extra"); //Check if extra is present
}

Answer 2

Use "has" method of JSONObject like this:

Array.getJSONObject(j).has("extra")