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Get Arraylist file json using java

I have problems with my code, I need to extract the "materias" markup in the arraylist. Example data:
[{
"name": "A114",
"grupo": "DAW2",
"tutor": 15,
"materias": ["DWES", "DWEC", "IW", "DAW", "IE"]
}]
I tried this, work but i need the content of the arraylist:
try { // this read the JSON file
line = new String(Files.readAllBytes(Paths.get("fileAulas")));
} catch (Exception ex) {
ex.printStackTrace();
}
JSONArray recs = new JSONArray(line);
for (Object rec : recs) {
Aula datos = new Aula();
JSONObject obj = ((JSONObject) rec);
String name = obj.getString("name");
//datos.setNombre(name);
String grupo = obj.getString("grupo");
//datos.setGrupo(grupo);
int tutor = obj.getInt("tutor");
//datos.setTutor(tutor);
}
My objetive is to read the arraylist and then datos.setArraylist to my another class. All works fine except read the arraylist
PD: I use java downloaded from Maven, to execute i use "javac -cp ./*: program.java"

materias is also an array, so you need something like:
JSONArray materias = obj.getJsonArray("materias");
List<String> materiasList = materias.getValuesAs(String.class);
This is not type-safe so you need to make sure the array will only have String values.
Also, if you are using Java 8, you can iterate over the values and store them manually (JsonArray is also a Collection<JsonValue>)

Quickly created short test implementation of your needs:
String json = "[{ \"name\":\"A114\",\"grupo\": \"DAW2\",\"tutor\":15,\"materias\": [\"DWES\",\"DWEC\",\"IW\",\"DAW\",\"IE\"]}]";
JSONArray objectArray = new JSONArray(json);
for (int x = 0; x < objectArray.length(); x++) {
JSONObject obj = objectArray.getJSONObject(x);
System.out.println("Name: " + obj.get("name"));
System.out.println("Grupo: " + obj.get("grupo"));
System.out.println("Tutor: " + obj.get("tutor"));
JSONArray materias = obj.getJSONArray("materias");
for (int y = 0; y < materias.length(); y++) {
System.out.println("Materia " + y + ": " + materias.get(y));
}
}
Output
Name: A114
Grupo: DAW2
Tutor: 15
Materia 0: DWES
Materia 1: DWEC
Materia 2: IW
Materia 3: DAW
Materia 4: IE

First gotta make your JSON Valid.
[{
"name": "A114",
"grupo": "DAW2",
"tutor": 15,
"materias": ["DWES", "DWEC", "IW", "DAW", "IE"]
}]
Secondly, you can try the following :
for (JsonElement rec : recs) {
Aula datos = new Aula();
JSONObject obj = rec.getAsJsonObject();
String name = obj.get("name").getAsString();
//datos.setNombre(name);
String grupo = obj.get("grupo").getAsString();
//datos.setGrupo(grupo);
int tutor = obj.get("tutor").getAsInt();
JsonObject obj = rec.getAsJsonObject();
JsonArray materias = obj.getAsJsonArray("materias");
List<String> materiasList = new ArrayList<>();
for (JsonElement item:
materias) {
materiasList.add(item.getAsString());
}
}

I believe that the syntax for an array in json is different that what you have in your file. For example - a simple complete json that contains an array of simple elements would be:
{"contacts":[
{ "firstName":"John", "lastName":"Doe" },
{ "firstName":"Jen", "lastName":"Smith" },
{ "firstName":"David", "lastName":"Jones" }
]}
In your text, you specify an array, without the opening and closing JSON '{' and '}'. Also, You would need to name the array element ("contacts" in the example above). I think that what you want would be (I used "arrayName" for the array element name):
{"arrayName":[{ "name":"A114","grupo": "DAW2","tutor":15,"materias":["DWES","DWEC","IW","DAW","IE"] },
{ "name":"121","grupo": "DAW1","tutor":8,"materias":["PROGRA","BD","SIS","LM","FOL"] },
{ "name":"A112","grupo": "AUTO1","tutor":5 },
{ "name":"A127","grupo": "ASIR1","tutor":2 },
{ "name":"A114","grupo": "SMR2","tutor":11 },
{ "name":"A128","grupo": "ASIR2","tutor":9,"materias":["IAW","ABD","ASIS","SI","IE"] },
{ "name":"A125","grupo": "ADM2","tutor":12 } ] }

reading data from nested JSON Object using java

i am struggling with reading some values from JSON object which i get it when i hit REST API..
MY GOAL: i need to iterate over each set of data inside data object array check the value of TRAN_ID and take action accordingly.
below is the format of data
{
"data": [
{
"CUST_ID": "CUST7",
"EXPRY_DATE": null,
"PARAMS": "[{TRAN_IND:savings},{TRAN_TYP:Debit},{country:US}]"
},
{
"CUST_ID": "CUST8",
"EXPRY_DATE": null,
"PARAMS": "[{TRAN_IND:current},{TRAN_TYP:Debit},{country:US}]"
}
]
}
it looks easy and i have tried multiple solutions out there on internet but i dont know it doesnt work for me and i get below error while reading "PARAMS" and converting it to JSONArray for further processing
Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to org.json.simple.JSONArray
What i have tried:
private static void jsonParser(String jsonStr) throws ParseException {
JSONObject data= (JSONObject)JSONValue.parse(jsonStr );
JSONArray jsonObj = (JSONArray)data.get("data");
JSONObject JsonRow = (JSONObject)jsonObj.get(0);
JSONArray servParam= (JSONArray) JsonRow.get("PARAMS");
String tran_ind=(String) servParam.get(0);
System.out.println( tran_ind);
}

I'm guessing this is what you what?
try{
JSONObject obj = new JSONObject(sample);
JSONArray data = obj.getJSONArray("data");
for(int i=0; i<data.length(); i++){
JSONObject detail = data.getJSONObject(i);
detail.getString("CUST_ID"); //here is the customer id
detail.getString("EXPRY_DATE"); //here is the exp date
JSONArray params = detail.getJSONArray("PARAMS");
for(int j=0; j<params.length(); j++){
// {TRAN_IND:current},{TRAN_TYP:Debit},{country:US}
JSONObject res = params.getJSONObject(j);
String tran_ind = res.toString();
String tran_type = res.toString();
String country = res.toString();
out.println(tran_ind + " " +tran_type + " " + country);
}
}
}catch (JSONException ex){
ex.printStackTrace();
}

Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to org.json.simple.JSONArray
=> Because you are trying to parse String value "[{TRAN_IND:savings},{TRAN_TYP:Debit},{country:US}]" into the JsonArray by code:
JSONArray servParam= (JSONArray) JsonRow.get("PARAMS");

Params seems to be a String, actually.
Don't write your own parser. If you only need to read that string in each element of the array, I would simply cast the whole JSON to a Map with Jackson:
HashMap<String,Object> parsed =
new ObjectMapper().readValue(JSON_SOURCE, HashMap.class);
and then iterate over the "data" element (which would be a list of maps).
List<Map> data = (List) parsed.get("data");

The real problem is that those are not nested JSON strings. That would be
"PARAMS": "[{\"TRAN_IND\":\"current\"},{\"TRAN_TYP\":\"Debit\"},{\"country\":\"US\"}]"
so "text" parts are surrounded by "-s inside (which have to be escaped as \"-s).
In that case you could write
String json=
"{\n"+
" \"data\": [\n"+
" {\n"+
" \"CUST_ID\": \"CUST7\",\n"+
" \"EXPRY_DATE\": null,\n"+
" \"PARAMS\": \"[{\\\"TRAN_IND\\\":\\\"savings\\\"},{\\\"TRAN_TYP\\\":\\\"Debit\\\"},{\\\"country\\\":\\\"US\\\"}]\"\n"+
" },\n"+
" {\n"+
" \"CUST_ID\": \"CUST8\",\n"+
" \"EXPRY_DATE\": null,\n"+
" \"PARAMS\": \"[{\\\"TRAN_IND\\\":\\\"current\\\"},{\\\"TRAN_TYP\\\":\\\"Debit\\\"},{\\\"country\\\":\\\"US\\\"}]\"\n"+
" }\n"+
" ]\n"+
"}";
// Print input for clarity:
System.out.println(json);
JSONObject data= (JSONObject)JSONValue.parse(json);
JSONArray jsonObj = (JSONArray)data.get("data");
JSONObject JsonRow = (JSONObject)jsonObj.get(0);
// parse nested JSON
JSONArray servParam= (JSONArray)JSONValue.parse((String)JsonRow.get("PARAMS"));
// array element is an object ({"TRAN_IND":"savings"}), so toString has to be used:
String tran_ind=servParam.get(0).toString();
System.out.println(tran_ind);
(The backslash-heaps are there because double-quotes had to be escaped in source code, and also the suggested escaped double quotes. So they would not appear in a JSON file. Try the code in action, it prints the JSON it works on)
So (JSONArray)JSONValue.parse((String)JsonRow.get("PARAMS")) would get and parse the nested JSON.
But now you either have to rework the code what generates your input, or parse the nested non-JSON manually.

You can use below code for parsing.
String servParam = (String) JsonRow.get("PARAMS");
String servParamSplitted[] = servParam.substring(1, servParam.length() - 1).split(",");
String traind_id[] = servParamSplitted[0].substring(1, servParamSplitted[0].length() - 1).split(":");
String train_id=traind_id[1];
I like to add that your JSON should be like below format.
{
"data": [
{
"CUST_ID": "CUST7",
"EXPRY_DATE": null,
"PARAMS": [{"TRAN_IND":"savings"},{"TRAN_TYP":"Debit"},{"country":"US"}]
},
{
"CUST_ID": "CUST8",
"EXPRY_DATE": null,
"PARAMS": [{"TRAN_IND":"current"},{"TRAN_TYP":"Debit"},{"country":"US"}]
}
]
}
So, we can parse it using below code.
JSONArray servParam = (JSONArray) JsonRow.get("PARAMS");
JSONObject jsonObjectTrainID = (JSONObject) servParam.get(0);
String TrainIDValue = (String) jsonObjectTrainID.get("TRAN_IND");

Reading JSON from Java

I have this JSON structure:
{"metrics":[{
"type": "sum",
"column": ["rsales", "nsales"]
},
{
"type":"count",
"column":["ptype", "plan"]
}]
}
I am trying to read that JSON from Java and want to the output to be like:
str_sum="Sum"
str_sum_array[]= {"rsales" ,"nsales"}
str_count="count"
str_count_array[]= {"ptype" ,"plan"}
Here is my code so far:
JSONArray jsonArray_Metric = (JSONArray) queryType.get("metrics");
for (int i = 0; i < jsonArray_Metric.length(); i++) {
JSONObject json_Metric = jsonArray_Metric.getJSONObject(i);
Iterator<String> keys_Metrict = json_Metric.keys();
while (keys_Metrict.hasNext()) {
String key_Metric = keys_Metrict.next();
// plz help
}
}
How can I complete the code to produce the desired output?

Instead of using iterator you can use simple for-loop as below ..
JSONParser parser = new JSONParser();
JSONObject object = (JSONObject) parser.parse(queryType);
JSONArray jsonArray_Metric = (JSONArray) object.get("metrics");
for (int index = 0; index < jsonArray_Metric.size(); index++) {
JSONObject item = (JSONObject) jsonArray_Metric.get(index);
String type = (String) item.get("type");
JSONArray column = (JSONArray) item.get("column");
System.out.println("str_sum store=\"" + type + "\"");
System.out.println("str_count_array[] store=" + column);
}
Sample Run
str_sum store="sum"
str_count_array[] store=["rsales","nsales"]
str_sum store="count"
str_count_array[] store=["ptype","plan"]
If you want JSONArray to be displayed with curly braces instead of default (actual) braces i.e. square braces then you could so something like this while printing or you can even delete them by replacing them with empty string "".
System.out.println("str_count_array[] store " + column.toString().replace("[", "{").replace("]", "}"));
You can format your display code as you like by playing around with println statement.

how to fetch JSONObject with array of objects

I have json string data like:
{"contactlist":["{"id":"1","mobile":"186010855","name":"Intex"}","{"id":"212","mobile":"980067","name":"pari"}"]}
I want to fetch all data means id,mobile and name for all..
So, I have Contact Class :
public class Contact {
private String id;
private String name;
private String mobile;
//getters and settrs & constructors
}
and for fetching I have tried:
String stringdata=
"{"contactlist":["{"id":"1","mobile":"186010855","name":"Intex"}","
{"id":"212","mobile":"980067","name":"pari"}"]}";
try{
Contact contact1 = new Contact();
contact1 = new Gson().fromJson(contactreceive, Contact.class);
Contact contact = new Contact(contact1.getId(),contact1.getName(),
contact1.getMobile());
System.out.println (contact);
}catch(Exception e){
}
But I can not fetch data like this..how can I fetch this json data?

Your JSON is invalid, as per #ShubhamChaurasia 's comment. The following JSON validates:
{
"contactlist": [{
"id": "1",
"mobile": "186010855",
"name": "Intex"
},
{
"id": "212",
"mobile": "980067",
"name": "pari"
}]
}
Escape this in Java as you have already been shown (with \") and this will stop your JSON validation errors. I recommend combining this with #Joopkins ' or #JanTheGun 's answer.
A good site I use for JSON validation is http://jsonlint.com/.

You need to escape the double quotes to get a valid json string. Then you can read the json array like this:
String stringdata = "{\"contactlist\":[{\"id\":\"1\",\"mobile\":\"186010855\",\"name\":\"Intex\"},{\"id\":\"212\",\"mobile\":\"980067\",\"name\":\"pari\"}]}";
JsonElement jsonElement = new JsonParser().parse(stringdata);
JsonObject jsonOject = jsonElement.getAsJsonObject();
JsonArray jsonArray = jsonOject.getAsJsonArray("contactlist");
for (JsonElement element : jsonArray) {
JsonObject obj = element.getAsJsonObject();
String id = obj.get("id").toString();
String name = obj.get("name").toString();
String mobile = obj.get("mobile").toString();
Contact contact = new Contact(id, name, mobile);
System.out.println("id: " + contact.getId());
System.out.println("name: " + contact.getName());
System.out.println("mobile: " + contact.getMobile());
System.out.println("");
}

You can convert the stringdata into a JSONArray containing a JSONObject for each contact.
JSONObject contactData = new JSONObject(stringdata);
JSONArray contactArray = contactData.getJSONArray("contactlist");
//Create an array of contacts to store the data
Contact[] contacts = new Contact[contactArray.length()];
//Step through the array of JSONObjects and convert them to your Java class
Gson gson = new Gson();
for(int i = 0; i < contactArray.length(); i++){
contacts[i] = gson.fromJson(
contactArray.getJSONObject(i).toString(), Contact.class);
}
Now you have an array of Contacts from your raw JSON data.

JSONObject contactData = new JSONObject(stringdata);
JSONArray contactArray = contactData.getJSONArray("contactlist");
for(int i=0;i<contactArray .length;i++){
JSONObject jsonObject=contactArray.getJSONObject(i));
String id=jsonObject.getString("id")
String key=jsonObject.getString("key")
}

Getting JSONObject from JSONArray [duplicate]

This question already has answers here:
Accessing members of items in a JSONArray with Java
(6 answers)
Closed 6 years ago.
I am in a bit of a fix regarding the JSONObject that I am getting as a response from the server.
jsonObj = new JSONObject(resultString);
JSONObject sync_reponse = jsonObj.getJSONObject("syncresponse");
String synckey_string = sync_reponse.getString("synckey");
JSONArray createdtrs_array = sync_reponse.getJSONArray("createdtrs");
JSONArray modtrs_array = sync_reponse.getJSONArray("modtrs");
JSONArray deletedtrs_array = sync_reponse.getJSONArray("deletedtrs");
String deleted_string = deletedtrs_array.toString();
{"syncresponse":{"synckey":"2011-09-30 14:52:00","createdtrs":[],"modtrs":[],"deletedtrs":[{"companyid":"UTB17","username":"DA","date":"2011-09-26","reportid":"31341"}]
as you can see in the response that I am getting I am parsing the JSONObject and creating syncresponse, synckey as a JSON object createdtrs, modtrs, deletedtrs as a JSONArray. I want to access the JSONObject from deletedtrs, so that I can split them apart and use the values. i.e I want to extract companyid, username, date etc.
How can I go about this ?
Thanks for your input.

JSONArray objects have a function getJSONObject(int index), you can loop through all of the JSONObjects by writing a simple for-loop:
JSONArray array;
for(int n = 0; n < array.length(); n++)
{
JSONObject object = array.getJSONObject(n);
// do some stuff....
}

Here is your json:
{
"syncresponse": {
"synckey": "2011-09-30 14:52:00",
"createdtrs": [
],
"modtrs": [
],
"deletedtrs": [
{
"companyid": "UTB17",
"username": "DA",
"date": "2011-09-26",
"reportid": "31341"
}
]
}
}
and it's parsing:
JSONObject object = new JSONObject(result);
String syncresponse = object.getString("syncresponse");
JSONObject object2 = new JSONObject(syncresponse);
String synckey = object2.getString("synckey");
JSONArray jArray1 = object2.getJSONArray("createdtrs");
JSONArray jArray2 = object2.getJSONArray("modtrs");
JSONArray jArray3 = object2.getJSONArray("deletedtrs");
for(int i = 0; i < jArray3 .length(); i++)
{
JSONObject object3 = jArray3.getJSONObject(i);
String comp_id = object3.getString("companyid");
String username = object3.getString("username");
String date = object3.getString("date");
String report_id = object3.getString("reportid");
}

JSONArray deletedtrs_array = sync_reponse.getJSONArray("deletedtrs");
for(int i = 0; deletedtrs_array.length(); i++){
JSONObject myObj = deletedtrs_array.getJSONObject(i);
}

{"syncresponse":{"synckey":"2011-09-30 14:52:00","createdtrs":[],"modtrs":[],"deletedtrs":[{"companyid":"UTB17","username":"DA","date":"2011-09-26","reportid":"31341"}]
The get companyid, username, date;
jsonObj.syncresponse.deletedtrs[0].companyid
jsonObj.syncresponse.deletedtrs[0].username
jsonObj.syncresponse.deletedtrs[0].date

start from
JSONArray deletedtrs_array = sync_reponse.getJSONArray("deletedtrs");
you can iterate through JSONArray and use values directly or create Objects of your own type
which will handle data fields inside of each deletedtrs_array member
Iterating
for(int i = 0; i < deletedtrs_array.length(); i++){
JSONObject obj = deletedtrs_array.getJSONObject(i);
Log.d("Item no."+i, obj.toString());
// create object of type DeletedTrsWrapper like this
DeletedTrsWrapper dtw = new DeletedTrsWrapper(obj);
// String company_id = obj.getString("companyid");
// String username = obj.getString("username");
// String date = obj.getString("date");
// int report_id = obj.getInt("reportid");
}
Own object type
class DeletedTrsWrapper {
public String company_id;
public String username;
public String date;
public int report_id;
public DeletedTrsWrapper(JSONObject obj){
company_id = obj.getString("companyid");
username = obj.getString("username");
date = obj.getString("date");
report_id = obj.getInt("reportid");
}
}

When using google gson library.
var getRowData =
[{
"dayOfWeek": "Sun",
"date": "11-Mar-2012",
"los": "1",
"specialEvent": "",
"lrv": "0"
},
{
"dayOfWeek": "Mon",
"date": "",
"los": "2",
"specialEvent": "",
"lrv": "0.16"
}];
JsonElement root = new JsonParser().parse(request.getParameter("getRowData"));
JsonArray jsonArray = root.getAsJsonArray();
JsonObject jsonObject1 = jsonArray.get(0).getAsJsonObject();
String dayOfWeek = jsonObject1.get("dayOfWeek").toString();
// when using jackson library
JsonFactory f = new JsonFactory();
ObjectMapper mapper = new ObjectMapper();
JsonParser jp = f.createJsonParser(getRowData);
// advance stream to START_ARRAY first:
jp.nextToken();
// and then each time, advance to opening START_OBJECT
while (jp.nextToken() == JsonToken.START_OBJECT) {
Map<String,Object> userData = mapper.readValue(jp, Map.class);
userData.get("dayOfWeek");
// process
// after binding, stream points to closing END_OBJECT
}

Make use of Android Volly library as much as possible. It maps your JSON reponse in respective class objects. You can add getter setter for that response model objects. And then you can access these JSON values/parameter using .operator like normal JAVA Object. It makes response handling very simple.