How to extract array values within nested JSON data

Question

I have JSON data in the following format:

{
  "data": {
    "id": 14810798216415,
    "name": "crescentbahuman.com",
    "is_organization": true,
    "email_domains": [
      "crescentbahuman.com"
    ]
  }
}

I want to get the string in the "email_domains" field. I wrote the following code as my attempt:

        JSONObject dataObject2= (JSONObject)jsonObject2.get("data");

        long id =  (long) dataObject2.get("id");
        System.out.println("worksapce id is: " + id);

        String name = (String) dataObject2.get("name");
        System.out.println("The worksapce name is: " + name);

        boolean is_organization = (boolean) dataObject2.get("is_organization");
        System.out.println("The workspace is organization: " + is_organization);            

        JSONArray email_domains = (JSONArray) jsonObject2.get("email_domains");

       Iterator<String> iterator = email_domains.iterator();
       while (iterator.hasNext()) {
        System.out.println(iterator.next());
       }

In this code to get "email_domains" only, a JSON Array object is created that get data from the JSON object and then its iterator is used to get values from within the array. However, it throws a NullPointerException on this line:

Iterator<String> iterator = email_domains.iterator();

I am stuck due to this problem. Can anyone kindly suggest a solution?

Is jsonObject the outer object or the data object? i.e., have you done jsonObject = (JSONObject) something.get("data");, or do you just need to do that? — Brett Kail
– Brett Kail, Commented May 16, 2015 at 6:13
How is your code even compiling? JSONArray does not have an iterator() method. — stackoverflowuser2010
– stackoverflowuser2010, Commented May 16, 2015 at 6:32
You are extracting "email_domains" from the variable jsonObject instead of extract it from dataObject2. dataObject2.get("name"); dataObject2.get("is_organization"); ¿jsonObject?.get("email_domains"); ??? — Chuidiang
– Chuidiang, Commented May 16, 2015 at 6:47
I am corrected this mistake but still null pointer exception — Abdul Majid Bajwa
– Abdul Majid Bajwa, Commented May 16, 2015 at 7:03

stackoverflowuser2010 · Accepted Answer · 2015-05-16 06:26:19Z

2

If you are using the JSON library from http://www.json.org/java/, then you should not be using JSONObject.get() so frequently. The library has other methods to get specific types, such as getLong(), getJSONArray(), and so forth. For your case with the "email_domains" field, you should try:

JSONArray array = dataObject2.getJSONArray("email_domains");
String value = array.getString(0);

answered May 16, 2015 at 6:26

stackoverflowuser2010

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user3337036 · Accepted Answer · 2015-05-16 07:26:48Z

1

org.json.JSONArray email_domains = (org.json.JSONArray) json.get("email_domains");
int length = email_domains.length();
 for(int i = length-1; i > 0; i--) {
    org.json.JSONObject jsonData = (org.json.JSONObject) email_domains.get(i);
    System.out.println(jsonData);
}

answered May 16, 2015 at 7:26

user3337036

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Richard Smith · Accepted Answer · 2015-05-16 06:16:25Z

0

My solution? I hate to be someone to offer a solution in another library... but look into google collections and the Gson helper. It can turn your Json into a map for you, and then back to json again when you are done.

Map map = gson.fromJson(jsonText, Map.class);

JsonArray's can then be cast into List's

answered May 16, 2015 at 6:16

Richard Smith

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Kushal · Accepted Answer · 2015-05-16 06:37:24Z

0

try this to fetch "email_domains"

JSONArray email_domains = ((JSONArray) jsonObject).get("email_domains");

or

JSONObject obj = new JSONObject(jsonObject.Tostring());

JSONArray email_domains = obj.optJSONArray("email_domains");

edited May 16, 2015 at 6:37

Kushal

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answered May 16, 2015 at 6:15

JohnTrack

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Kushal · Accepted Answer · 2015-05-16 08:09:57Z

0

"email_address" is JSONArray so we need to fetch this like

JSONArray email_domains = (JSONArray) dataObject2.getJSONArray("email_domains");
email_domains.get(0); // this will return crescentbahuman.com

edited May 16, 2015 at 8:09

answered May 16, 2015 at 6:28

Kushal

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3 Comments

Abdul Majid Bajwa Over a year ago

error because there is no method named getJSONArray

Kushal Over a year ago

My mistake in using.. try dataObject2.getJSONArray("email_domains");

Kushal Over a year ago

As posted by @stackoverflowuser2010 you can use above solution and this works well

Safwan Hijazi · Accepted Answer · 2015-05-17 06:52:44Z

Use this implementation

import java.lang.reflect.Field;
import java.util.List;
import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class JsonConvertor {

private static GsonBuilder gsonBuilder;
private static Gson gson;

private JsonConvertor() {

}
public static Object fromJson(String json, Class clz)
{
    gson=new Gson();
    return gson.fromJson(json,clz);
}

public static String toJson(Object obj) {
    gsonBuilder = new GsonBuilder();
    gsonBuilder = gsonBuilder
            .addSerializationExclusionStrategy(new CustomIclusionStrategy(
                    obj.getClass()));
    gson = gsonBuilder.create();
    String json = gson.toJson(obj);
    return json;
}

}

class CustomIclusionStrategy implements ExclusionStrategy {

private Class classToIclude;

private Field[] declaredFields;


private List<FieldAttributes> fields;

public CustomIclusionStrategy(List<FieldAttributes> fields) {
    this.fields = fields;
}

public CustomIclusionStrategy(Class classToIclude) {
    this.classToIclude = classToIclude;
    this.declaredFields=classToIclude.getDeclaredFields();

}

// called only if shouldSkipClass returns false
@Override
public boolean shouldSkipField(FieldAttributes f) {

    try {
        classToIclude.getSuperclass().getDeclaredField(f.getName());
        System.out.println(f.getName());
        return true;
    } catch (Exception e) {
    } 
    return false;

}

@Override
public boolean shouldSkipClass(Class<?> clazz) {
    // if returns false shouldSkipField will be called, otherwise 
  //shouldSkipField will not be called
    return false;
 }
}



public class Org {
private Data data;

public Org(Data data) {
    super();
    this.data = data;
}

public Data getData() {
    return data;
}

public void setData(Data data) {
    this.data = data;
}

public String toJson()
{
    return JsonConvertor.toJson(this);
}
public static void main(String[] args) {

    String json="{\"data\": {\"id\":\"1\",\"name\":\"org1\",\"is_organization\":true,\"email_domains\":   [\"email1\",\"email2\",\"email3\",\"email4\"]}}";

    Org o=(Org) JsonConvertor.fromJson(json, Org.class);

    System.out.println(o.getData().getEmail_domains());
}

}

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