JAVA Access json String

Question

Im working on a android app and Im having trouble with a Json String. I want to access "Naam" under "Docenten" in the following Json:

{  
"Items":[  
  {  
     "Id":2157750,
     "Links":[  
        {  
           "Rel":"Self",
           "Href":"/api/personen/11824/afspraken/2157750"
        },
        {  
           "Rel":"Next",
           "Href":"/api/personen/11824/afspraken/2157661"
        }
     ],
     "Start":"2015-11-16T07:30:00.0000000Z",
     "Einde":"2015-11-16T08:20:00.0000000Z",
     "LesuurVan":1,
     "LesuurTotMet":1,
     "DuurtHeleDag":false,
     "Omschrijving":"du - rec - G3A",
     "Lokatie":"103",
     "Status":7,
     "Type":13,
     "WeergaveType":0,
     "Inhoud":"<html><head></head><body style=\"font-family: 'Arial'; font-size: 12px\"><p style=\"margin: 0px 0px 10px\">lernen für Klassenarbeit,<br/>fertigmachen: 17.4</p></body></html>",
     "InfoType":1,
     "Aantekening":null,
     "Afgerond":false,
     "Vakken":[  
        {  
           "Id":3,
           "Naam":"Duits"
        }
     ],
     "Docenten":[  
        {  
           "Id":706,
           "Naam":"C. Reuten",
           "Docentcode":"rec"
        }
     ],
     "Lokalen":[  
        {  
           "Naam":"103"
        }
     ],
     "Groepen":null,
     "OpdrachtId":0,
     "HeeftBijlagen":false,
     "Bijlagen":null
  },
  ...

This is my code but it gives a NullPointer Error:

private void handlejson_agenda(String input){
    if(input != null && input != "[]" && input != "") {
        try {
            JSONObject jsonRootObject = new JSONObject(input);

            //Get the instance of JSONArray that contains JSONObjects
            JSONArray jsonArray = jsonRootObject.optJSONArray("Items");

            //Iterate the jsonArray and print the info of JSONObjects
            if(jsonArray == null){
                //niks
            } else {
                for (int i = 0; i < jsonArray.length(); i++) {
                    JSONObject jsonObject = jsonArray.getJSONObject(i);

                    String name = jsonObject.optString("Omschrijving").toString();
                    String lesuurvan = jsonObject.optString("LesuurVan").toString();
                    String lesuurtot = jsonObject.optString("LesuurTotMet").toString();
                    String lokatie = jsonObject.optString("Lokatie").toString();
                    String status = jsonObject.optString("Status").toString();
                    String datumvan = jsonObject.optString("Start").toString();
                    String datumtot = jsonObject.optString("Einde").toString();
                    String leraar = jsonObject.optJSONArray("Docenten").optString("Naam").toString();
                    String inhoudles = jsonObject.optString("Inhoud").toString();
                    String datumvanconverted = datumvan.substring(0, 10);
                    DateFormat dateFormat = new SimpleDateFormat("HH:mm");
                    ...

Everything works except for the "Leraar" String, I hope someone can help me.

-Z3r0byte

Possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — ΦXocę 웃 Пepeúpa ツ, Dec 01 '15 at 19:25
`NullPointer`? that's doubtful, considering your code does not compile. — njzk2, Dec 01 '15 at 19:49

score 3 · Accepted Answer · answered Dec 01 '15 at 19:19

3

This may work:

String leraar = jsonObject.optJSONArray("Docenten").getJSONObject(0).optString("Naam").toString();

So Docenten is a JSONArray that it may need to be accessed with index.

answered Dec 01 '15 at 19:19

hata

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score 0 · Answer 2 · answered Dec 01 '15 at 19:18

I would recommand you to create an Item class with the corresponding fields and then to use ObjectMapper to parse json to java Object.

private ObjectMapper mapper = new ObjectMapper();
Item item = mapper.readValue(input, new TypeReference<Item>(){});
item.getDocenten().get(0).getNaam();

And the Item.class

public class Item {
    // attributes
    // constructor
    // getter + setter
}

It will be much easier after that

JAVA Access json String

2 Answers2