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Access intended values in JSON file using JAVA

This is the JSON file I am working with
{"sentiment":
{"document":
{
"label": "positive",
"score": 0.53777
}
}
}
I need to access the value in label and score. using java. How can I do that?
Find below the code I am using right now:
JSONParser parser = new JSONParser();
try
{
Object object = parser
.parse(new FileReader("output_nlu_sentiment.json"));
//convert Object to JSONObject
JSONObject jsonObject = new JSONObject();
JSONObject sentimentobject= new JSONObject();
JSONObject documentobject = new JSONObject();
sentimentobject= (JSONObject) jsonObject.get("sentiment");
documentobject= (JSONObject) sentimentobject.get("document");
String label = (String) documentobject.get("label");
//float score = (float) jsonObject.get("score");
System.out.println(label);
String test = (String) sentimentobject.get("label");
System.out.println(test);
} catch(FileNotFoundException fe)
{
fe.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}
Why is it printing the value as null.

You might want to have a look at JacksonXml for json parsing.
Right now the problem is that you're not using the JsonObject returned by parser.parse(...).
Instead you use the get method on objects you just created. This of course means that you don't getthe valie you want to.

Try to use following code (JSONObject jsonObject = (JSONObject) object instead of JSONObject jsonObject = new JSONObject();), because you didn't use object at all, just create new empty JSONObject.
JSONParser parser = new JSONParser();
try
{
Object object = parser
.parse(new FileReader("output_nlu_sentiment.json"));
//convert Object to JSONObject
JSONObject jsonObject = (JSONObject) object;
JSONObject sentimentobject = (JSONObject) jsonObject.get("sentiment");
JSONObject documentobject= (JSONObject) sentimentobject.get("document");
String label = (String) documentobject.get("label");
System.out.println(label);
float score = (float) documentobject.get("score");
System.out.println(score );
}catch(FileNotFoundException fe)
{
fe.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}

You have to make use of object created in Object object = parser.parse(new FileReader("output_nlu_sentiment.json")); while creating the jsonObject
For that you can look at the code below:
Object object = parser
.parse(new FileReader("file2.json"));
//convert Object to JSONObject
JSONObject jsonObject = (JSONObject) object;
JSONObject sentimentobject= new JSONObject();
JSONObject documentobject = new JSONObject();
sentimentobject= (JSONObject) jsonObject.get("sentiment");
documentobject= (JSONObject) sentimentobject.get("document");
String label = (String) documentobject.get("label");
//float score = (float) jsonObject.get("score");
System.out.println(label);
String test = (String) sentimentobject.get("label");
You will get the positive printed on console.

you should see the content in para 'sentimentobject',force convert into class JSONObject can not get the value you want.

I prefer the FasterXML Jackson support to parse JSON into plain old Java objects (POJOs). These POJOs are often called Data Transfer Objects (DTOs) and give you a way to turn your JSON fields into properly typed members of the corresponding DTO.
Here is an example method to do that. The ObjectMapper(s) are generally maintained as statics somewhere else because FasterXML's implementation caches information to improve efficiency of object mapping operations.
static final ObjectMapper mapper = new ObjectMapper();
This is the JSON deserialization method:
public static <T> T deserializeJSON(
final ObjectMapper mapper, final InputStream json,
final Class<T> clazz)
throws JsonParseException, UnrecognizedPropertyException,
JsonMappingException, IOException
{
final String sourceMethod = "deserializeJSON";
logger.entering(sourceClass, sourceMethod);
/*
* Use Jackson support to map the JSON into a POJO for us to process.
*/
T pojoClazz;
pojoClazz = mapper.readValue(json, clazz);
logger.exiting(sourceClass, sourceMethod);
return pojoClazz;
}
Assuming I have a class called FooDTO, which has the appropriate Jackson annotations/getters/setters (note you must always provide a default empty public constructor), you can do this:
FooDTO foo = deserializeJSON(mapper, inputstream, FooDTO.class);
The deserialization throws a few different exceptions (all of which have IOException as their parent class) that you will need to handle or throw back to the caller.

Here besides of the correction alreay addressed in comments and other answers, I include some other changes you can benefit of:
It is not necessary to initialize the JSONObjects with a new instance that is going to be ovewritten in the next line.
You can use getJSONObject(), getString(), getFloat() instead of get(), in this way you don't need to cast the result.
public void parseJson() {
JSONParser parser = new JSONParser();
try
{
JSONObject jsonObject = new JSONParser().parse(new FileReader("output_nlu_sentiment.json"));
JSONObject sentimentobject= null;
JSONObject documentobject = null;
sentimentobject= jsonObject.getJSONObject("sentiment");
documentobject= sentimentobject.getJSONObject("document");
String label = documentobject.getString("label");
float score = documentobject.getFloat("score");
String output = String.format("Label: %s Score: %f", label, score);
System.out.println(output);
}catch(FileNotFoundException fe){
fe.printStackTrace();
}catch(Exception e){
e.printStackTrace();
}
}
Also for this kind of objects, where the attribute names could act as object properties, I suggest you take a look at Gson library. After modeling the json as a composition of POJOs, the parsing takes 1 line of code.

Query a JSON Object in Java by index

In Java, is there a way to retrieve a piece of information from a JSON object by index? I am accessing a financial data table on quandl and want to return the most recent mortgage rate posted in the table. The key is the date the rate was posted in string form. The key for the most recent data will change weekly but the data I want will always be the first key-value pair in the table.
I was able to do this in JavaScript in about 5 minutes. But it seems more cumbersome in Java. Below is the iteration of my code that seems to be closest to getting me where I want to go. I am able to return the first key-value pair set in the table as an object in Java, which is ... ["2017-12-14",3.93]. The final step is eluding me. How do I grab the 3.93 and return that? Or is there a better way to go about this?
double baseRate = 0.0;
default double getBaseRate() throws MalformedURLException {
try {
// make a GET request
URL url = new URL("https://www.quandl.com/api/v3/datasets/FMAC/30US.json?api_key=-c-s9zf8s1NdLbhVin1p");
HttpURLConnection request = (HttpURLConnection) url.openConnection();
request.connect();
InputStreamReader is = new InputStreamReader((InputStream) request.getContent());
// Convert response stream to a JSON object
JsonReader reader = Json.createReader(is);
JsonObject obj = reader.readObject();
reader.close();
request.disconnect();
// Drill down to the desired piece of data
JsonObject dataset = obj.getJsonObject("dataset");
JsonArray data = dataset.getJsonArray("data");
Object currentData = data.get(0);
System.out.println(currentData);
} catch (IOException e) {
e.printStackTrace();
}
return baseRate;
}

I think that you need to go down another level of array to access the value you required.
JsonArray data = dataset.getJsonArray("data");
JsonArray firstPieceOfData = data.get(0);
Object firstRate = firstPieceOfData.get(1);

If you use Jackson for reading your JSON you can use the .at() method which allows you to access the node's value via a JSON Pointer Expression which in your case would be "/dataset/data/0/1"
I've truncated your json for the purpose of this demo:
String jsonString = "{\"dataset\":{\"id\":4644596,\"dataset_code\":\"30US\",\"database_code\":\"FMAC\",\"name\":\"30-Year Fixed Rate Mortgage Average in the United States\",\"description\":\"Units: Percent\\u003cbr\\u003e\\u003cbr\\u003eNot Seasonally Adjusted\",\"refreshed_at\":\"2017-12-18T04:09:32.892Z\",\"newest_available_date\":\"2017-12-14\",\"oldest_available_date\":\"1971-04-02\",\"column_names\":[\"Date\",\"Value\"],\"frequency\":\"weekly\",\"type\":\"Time Series\",\"premium\":false,\"limit\":null,\"transform\":null,\"column_index\":null,\"start_date\":\"1971-04-02\",\"end_date\":\"2017-12-14\",\"data\":[[\"2017-12-14\",3.93],[\"2017-12-07\",3.94],[\"2017-11-30\",3.9]],\"collapse\":null,\"order\":null,\"database_id\":582}}";
ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNodes = mapper.createObjectNode();
try {
jsonNodes = mapper.readTree(jsonString);
} catch (IOException e) {
//e.printStackTrace();
}
System.out.println(jsonNodes.at("/dataset/data/0/1").asDouble());// 3.93

How to get the fields of a JSON object in android studio?

I have an android app and a Web Service. When I want to edit some register I have to get the whole record from the database and put every field in a Edit Text.
The Web Service return me this to the android app
[{"id":"6","0":"6","tipo":"No Oxidado","1":"No Oxidado","fecha":"2015-02-02","2":"2015-02-02","ubicacion":"-1.555505, -6.6171","3":"-1.555505, -6.6171","persona":"Laura Morales","4":"Laura Morales","fotografia":"-","5":"-"}]
And I have a variable called "result" that have this JSON string
How do I put every field in a independent edit text in my Android App?
something like:
txtid.setText(result[0]);
txtType.setText(result[1]);
txtDate.setText(result[2]);
txtLocation.setText(result[3]);
txtPerson.setText(result[4]);
where "result" is my JSON string.

try below code.
if you have more than one json object in array
String response = "[{"id":"6","0":"6","tipo":"No Oxidado","1":"No Oxidado","fecha":"2015-02-02","2":"2015-02-02","ubicacion":"-1.555505, -6.6171","3":"-1.555505, -6.6171","persona":"Laura Morales","4":"Laura Morales","fotografia":"-","5":"-"}]"
try {
JSONArray jsonArray = new JSONArray(response);
for (int i =0; i<jsonArray.length();i++){
JSONObject jsonObject = jsonArray.getJSONObject(i);
txtid.setText(jsonObject.getString("0"));
txtType.setText(jsonObject.getString("1"));
txtDate.setText(jsonObject.getString("2"));
}
} catch (JSONException e) {
e.printStackTrace();
}
And if you have only one object in array then no need to use for loop use directly this way
try {
JSONArray jsonArray = new JSONArray(response);
JSONObject jsonObject = jsonArray.getJSONObject(0);
txtid.setText(jsonObject.getString("0"));
txtType.setText(jsonObject.getString("1"));
txtDate.setText(jsonObject.getString("2"));
} catch (JSONException e) {
e.printStackTrace();
}

there is a library to convert Json object to android model that call GSON
at first create a model with your input object like below:
class InputModel {
String id;
String 0; //it's better to change this object name
String tipo;
...
}
next, you can use Gson to bind your input to your model. it should be something like this:
InputModel mInput = new Gson().fromJson(data);
ps1: data is your input string
ps2: if you want the name of your input be different with your input name, you can use an annotation like this:
#SerializedName("id")
String productId;

Dynamic JSON issue

My JSON Structure will vary depend on the request. But the content inside each element remain same. For Example:
JSON1:
{
"h1": {
"s1":"s2"
},
"c1": {
"t1:""t2"
}
}
JSON2:
{
"h1": {
"s1":"s2"
},
"c2": {
"x1:""x2"
}
}
In the above example, elements inside h1,c1 and c2 are constant. Please let me know how to convert JSON to JAVA Object
Regards
Udhaya

First of all You need to understand Json Structure cause above format is incorrect visit this
and this
And you can use Google Gson or Json for parsing the result json String .

"t1:""t2" json format incorrect
Used
"t1":"t2"
Instead of
"t1:""t2"
and also used
"x1": "x2"
Instead of
"x1:""X2"
Code to take in java
try {
JSONObject jsonObject = new JSONObject(response);
JSONObject jsonsubObject = jsonObject.getJSONObject("h1");
String s1 = jsonsubObject.getString("s2");
JSONObject jsonsubObject1 = jsonObject.getJSONObject("c1");
String t1 = jsonsubObject1 .getString("t2");
}
catch (JSONException e) {
e.printStackTrace();
}

Use Google Gson:
Gson gson = new Gson();
ClassName object;
try {
object = gson.fromJson(json, ClassName.class);
} catch (com.google.gson.JsonSyntaxException ex) {
//the json wasn't valid json
}
String validJson = gson.toJson(obj); //obj is an instance of any class
json must be a valid JSON String

import org.json.JSONObject;
you can simple pass your data in constructor of JSONObject it automatically handle, you need to throws JSONException which may occur during conversion id format of data is not correct
String data = "{'h1':{'s1':'s2'},'c1':{'t1:''t2'}}";
JSONObject jsnobject = new JSONObject(data);

JSON payload construction Android

I want to construct a JSON payload of this:
{
"aps": {
"badge": 15,
"alert": "Hello from Urban Airship!",
"sound": "cat.caf"
}
}
I tried with this thing :
JSONObject json = new JSONObject();
JSONObject badge=new JSONObject();
JSONObject alert=new JSONObject();
JSONObject sound=new JSONObject();
badge.put("badge",15);
json.put("aps",badge);
sound.put("sound",getResources().openRawResource(R.raw.cat));
json.put("aps",alert);
alert.put("alert", "Hello from Uday!");
json.put("aps",sound);
but it full payload is obtaining:when I print
am getting like half of payload like this:
{"aps":{"sound":"cat.caf"}}
its overriding, but
How do it in a correct way
Thanks

I am not sure what you are looking for, but considering that you want to create a JSON String.
try {
JSONObject json = new JSONObject();
JSONObject aps = new JSONObject();
aps.put("badge", 15);
aps.put("alert", "Hello from Urban Airship!");
aps.put("sound", "cat.caf");
Log.d("my json string", json.put("aps", aps).toString(1));
} catch (JSONException e) {
e.printStackTrace();
}

openRawResource() returns an InputStream.. you might want to try reading it using an InputStreamReader?