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Retrieve data from JSON Object using JSON Simple library

This is the JSON object printed to screen:
{"UserName":"myUsername","Address":"myAddress","Password":"myPassword"}
In the following code, what value goes in data_obj.get() & in obj.get() to retrieve UserName value myUsername from JSON Object?
JSONObject obj = (JSONObject) data_obj.get();
System.out.println(obj.get("UserName"));
I tried this
JSONObject obj = (JSONObject) data_obj.get(0);
//Get the required data using its key
System.out.println(obj.get("UserName"));
but I got null pointer and was expecting the data for UserName field equals myUsername.

You're probably performing a redundant step.
That's how the data you've shared can be parsed:
String jsonStr = """
{"UserName":"myUsername","Address":"myAddress","Password":"myPassword"}
""";
JSONObject jsonObject = new JSONObject(jsonStr);
System.out.println(jsonObject.get("UserName"));
System.out.println(jsonObject.get("Address"));
System.out.println(jsonObject.get("Password"));
Output:
myUsername
myAddress
myPassword

Parse the JSON response

i am trying to phrase the below json response and the get the "message" and "WORKORDERID" data in java
{
"operation": {
"result": {
"message": " successfully.",
"status": "Success"
},
"Details": {
"SUBJECT": "qqq",
"WORKORDERID": "800841"
}
}
}
Below is my code
JSONObject inputs = new JSONObject(jsonResponse);
JSONObject jsonobject = (JSONObject) inputs.get("operation");
String s = jsonobject.getString("message");
system.out.println("s");

Your objects are nested 2 times, therefore you should do:
JSONObject inputs = new JSONObject(jsonResponse);
JSONObject operation= (JSONObject) inputs.get("operation");
JSONObject result= (JSONObject) operation.get("result");
JSONObject details= (JSONObject) operation.get("Details");
String message = result.getString("message");
String workerId = details.getString("WORKORDERID");

JSONObject is somethink like Map-Wrapper, so you can think, that your JSON data-structure is Map<Map<Map<String, Object>, Object>, Object>. So, firstly you need to access to datas by first key (operation), secondly (result) and after that, you can access to desired field (message).
Note, that value of Map is Object, so you will need to cast your type to JSONObject.

sometimes JSONObject class is not found in java. so you will need to add jar
try{
// build the json object as follows
JSONObject jo = new JSONObject(jsonString);
// get operation as json object
JSONObject operation= (JSONObject) jo.get("operation");
// get result as json object
JSONObject result= (JSONObject) jo.get("result");
JSONObject details= (JSONObject) jo.get("Details");
// get string from the json object
String message = jo.getString("message");
String workerId = jo.getString("WORKORDERID");
}catch(JSONException e){
System.out.println(e.getMessage());
}

Convert string to json doesn't work java

I have a problem with convert string to json.
Namely, my json string is:
{"serverId":2,"deviceId":736,"analysisDate":"2017-05-11T07:20:27.713Z","eventType":"Logs","eventAttributes":[{"name":"level","value":"INFO"},{"name":"type","value":"Video Blocked On"},{"name":"cameraId","value":"722"},{"name":"userId","value":"1"}]}
My code:
try {
JSONObject object = new JSONObject(jsonString);
JSONArray array = object.getJSONArray("eventAttributes");
System.out.println("ARRAY: " + array);
for (int i = 0; i < array.length(); i++) {
JSONObject obj = new JSONObject(array.getJSONObject(i));
System.out.println("OBJ: " + obj);
}
} catch (JSONException ex) {
Exceptions.printStackTrace(ex);
}
System.out.println array is:
[{"name":"level","value":"INFO"},{"name":"type","value":"Video Blocked On"},{"name":"cameraId","value":"722"},{"name":"userId","value":"1"}]
but if I print obj is "{}", four times. So it is correct, because array has 4 elements, but why it is empty object? I'm using org.json.
Thanks

array.getJSONObject(i) is already returning you an object of type JSONObject you dont need to pass it to constructor of JSONObject class.
simply write
...
for (int i = 0; i < array.length(); i++) {
JSONObject obj = array.getJSONObject(i);
System.out.println("OBJ: " + obj);
}
...

You're calling the JSONObject(Object) constructor, passing in a JSONObject (the element in the array). That constructor is documented as:
Construct a JSONObject from an Object using bean getters. It reflects on
all of the public methods of the object. For each of the methods with no
parameters and a name starting with "get" or
"is" followed by an uppercase letter, the method is invoked,
and a key and the value returned from the getter method are put into the
new JSONObject. [...]
Now JSONObject itself doesn't have anything that fits a bean getter, so you end up with no keys. You don't want to treat the JSONObject as a bean.
That's why your current code doesn't work. To fix it, just don't call the constructor - instead, use the fact that the array element is already a JSONObject:
JSONObject obj = array.getJSONObject(i);
Output with that change:
OBJ: {"name":"level","value":"INFO"}
OBJ: {"name":"type","value":"Video Blocked On"}
OBJ: {"name":"cameraId","value":"722"}
OBJ: {"name":"userId","value":"1"}

If you consider following example you can do it in 3 ways :
jsonString = {
"name" : "John",
"sport" : "Soccer",
"age" : 25,
"id" : 100,
"score" : [ 2, 1, 4, 5, 0, 1, 2, 3, 1]
}
String to JSON Object using GSON
Gson g = new Gson();
Player p = g.fromJson(jsonString, Player.class)
You can also convert Java object to JSON by using method toJson()
String str = g.toJson(p);
JSON String to Java object using JSON-Simple
JSONParser parser = new JSONParser();
JSONObject json = (JSONObject) parser.parse(stringToParse);
String to JSON - Jackson Example
Player john = new ObjectMapper().readValue(jsonString, Player.class);

Json array inside array retrieve values Android

i m trying to get values from JSONArray inside array, i m able to retrieve whole JSON values into JSONArray successfully but not able to retrieve values inside JSONArray. When i convert JSONArray to JSONObject to get values stored inside JSONArray. It gives error: org.json.JSONException: No value for "banner"
Here is JSON code, i verified JSON code with jsonlint.com and it showed JSON is Validate,
[
{"code":"banner","moduletitle":0,
"banner":
[
{"image":"http://imageurl"},
{"image":"http://imageurl"},
{"image":"http://imageurl"}
]
}
]
I m trying to get this from 3 hour but no luck. i m new in JSON and do not know how JSON Actually work, and also read abut GSON Library to get JSON values. here is My Java code.
JSONArray jsonObj = null;
String image_url = "";
String banner_code ="";
try {
jsonObj =new JSONArray(lib_function.getJSONUrl( jsontags.Top_Banner_JOSN_URLs));
Log.d("value retrun :","" +jsonObj);
//---vlaue is coming and print in Log ----//
} catch (JSONException e) {
Log.v("Error in Parser :", " " + e);
Log.d("no value retrun :", "failed to convert");
}
try{
JSONObject jo = new JSONObject();
JSONArray ja = new JSONArray();
// populate the array
jo.put("arrayName", jsonObj);
JSONArray subArray = jo.getJSONArray("banner");
image_url= subArray.getString(Integer.parseInt("image"));
Log.d("banner code",""+subArray);
}catch(Exception e)
{
Log.d("not working",""+e);
}
I folllow this question but luck:
How to parse JSON Array inside another JSON Array in Android
If anyone suggest, what i m doing wrong will be appreciate. or let me know, where i can get more information about json
UPDATE thanks too all to give their precious time for answering my stupid question. All answers are correct , but i can accept only one answer. A Big thanks to all

Here:
JSONObject jo = new JSONObject();
JSONArray ja = new JSONArray();
// populate the array
jo.put("arrayName", jsonObj);
Because parsing jsonObj JSONArray so no need to create new JSONArray and JSONObject to extract it from jsonObj. remove all above three lines.
banner JSONArray is inside JSONObject which is contained by jsonObj JSONArray, get it as:
JSONObject jsonObject=jsonObj.optJSONObject(0);
JSONArray subArray = jsonObject.getJSONArray("banner");
// get code key from `jsonObject`
String strCode=jsonObject.optString("code");
// get all images urls from `subArray`
for(int index=0;index<subArray.length();index++){
JSONObject imgJSONObject=subArray.optJSONObject(index);
// get image urls
String strImgURL=imgJSONObject.optString("image");
}
Also, if jsonObj JSONArray contains multiple JSONObject's then use for-loop to iterate it.

I am assuming you have the rest of the values accessible to you, so posting just this snippet.
code=jsonObject.getString("code");
moduletitle=jsonObject.getString("moduletitle");
banner=jsonObject.getJSONArray("banner");

jsonObj =new JSONArray(lib_function.getJSONUrl( jsontags.Top_Banner_JOSN_URLs);
From above line you will get JSONArray. So now loop it and get you banner JSONArray.Again loop bannerArray and you will get image Urls

If You want value of "image" which is in json arrray than
String response = "your response";
try{
JsonArray jAry = new JsonArray(response);
JsonObject jObj = jAry.getJsonObject(0);
JsonArray jsonBanner = jObj.getJsonArray("banner");
JsonObject temp;
for(int i=0;i<jsonBanner.length;i++){
temp = jsonBanner.getJsonObject(i);
String image = temp.optString("image");
}
}

Java JSON parse array

I am using the following library to parse an object:
{"name": "web", "services": []}
And the following code
import com.json.parsers.JSONParser;
JSONParser parser = new JSONParser();
Object obj = parser.parseJson(stringJson);
when the array services is empty, it displays the following error
#Key-Heirarchy::root/services[0]/ #Key:: Value is expected but found empty...#Position::29
if the array services has an element everything works fine
{"name": "web", "services": ["one"]}
How can I fix this?
Thanks

Try using org.json.simple.parser.JSONParser
Something like this:
JSONParser parser = new JSONParser();
JSONObject jsonObject = (JSONObject) parser.parse(stringJson);
Now to access the fields, you can do this:
JSONObject name = jsonObject.get("name"); //gives you 'web'
And services is a JSONArray, so fetch it in JSONArray. Like this:
JSONArray services = jsonObject.get("services");
Now, you can iterate through this services JSONArray as well.
Iterator<JSONObject> iterator = services.iterator();
// iterate through json array
while (iterator.hasNext()) {
// do something. Fetch fields in services array.
}
Hope this would solve your problem.

Why do you need parser?
try this:-
String stringJson = "{\"name\": \"web\", \"services\": []}";
JSONObject obj = JSONObject.fromObject(stringJson);
System.out.println(obj);
System.out.println(obj.get("name"));
System.out.println(obj.get("services"));
JSONArray arr = obj.getJSONArray("services");
System.out.println(arr.size());

I solve the problen with https://github.com/ralfstx/minimal-json
Reading JSON
Read a JSON object or array from a Reader or a String:
JsonObject jsonObject = JsonObject.readFrom( jsonString );
JsonArray jsonArray = JsonArray.readFrom( jsonReader );
Access the contents of a JSON object:
String name = jsonObject.get( "name" ).asString();
int age = jsonObject.get( "age" ).asInt(); // asLong(), asFloat(), asDouble(), ...
Access the contents of a JSON array:
String name = jsonArray.get( 0 ).asString();
int age = jsonArray.get( 1 ).asInt(); // asLong(), asFloat(), asDouble(), ...