I am trying to add specific values from the following JSON to a Java ArrayList. I would then like to use this ArrayList within a JSP. This is the JSON:
{
"page": 1,
"rpp": 3,
"total": 3294,
"request_time": "2018-04-23T16:10:20+01:00",
"stops": [
{
"atcocode": "370023715",
"longitude": -1.46616,
"latitude": 53.38248,
"distance": 57
},
{
"atcocode": "370027281",
"longitude": -1.46583,
"latitude": 53.38228,
"distance": 77
},
{
"atcocode": "370022803",
"longitude": -1.46616,
"latitude": 53.38227,
"distance": 80
}
]
}
I would like to add each longitude and latitude elements from under the "stops" subtree into 2 different ArrayLists. This is my attempted code for that:
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
try {
String json = readUrl (link);
JsonParser parser = new JsonParser();
JsonElement element = parser . parse (json);
if (element.isJsonObject()) {
JsonObject bus = element . getAsJsonObject ();
JsonArray array = bus . getAsJsonArray ("stops");
for (int i = 0; i < array.size(); i++) {
List<String> longitudes = new ArrayList<String>();
List<String> latitudes = new ArrayList<String>();
longitudes.add(array.get(i)).get("longitude");
latitudes.add(array.get(i)).get("latitude");
request.setAttribute("longitudes", longitudes);
request.setAttribute("latitudes", latitudes);
RequestDispatcher dispatcher = request . getRequestDispatcher ("latlong.jsp");
dispatcher.forward(request, response);
}
}
}
}
i get the following error of: "error: incompatible types: JsonElement cannot be converted to String"
Thank you in advance!
One other error you have is that the longitudes, latitudes lists are inside of the loop.
Here is a simple testable piece of code which extracts the data from the JSON and can be tested locally. You can adapt it to your purposes ...
public static void main(String[] args) {
String json = "{\n" +
"\"page\": 1,\n" +
"\"rpp\": 3,\n" +
"\"total\": 3294,\n" +
"\"request_time\": \"2018-04-23T16:10:20+01:00\",\n" +
"\"stops\": [\n" +
"{\n" +
" \"atcocode\": \"370023715\",\n" +
" \"longitude\": -1.46616,\n" +
" \"latitude\": 53.38248,\n" +
" \"distance\": 57\n" +
"},\n" +
"{\n" +
" \"atcocode\": \"370027281\", \n" +
" \"longitude\": -1.46583,\n" +
" \"latitude\": 53.38228,\n" +
" \"distance\": 77\n" +
"},\n" +
"{\n" +
" \"atcocode\": \"370022803\",\n" +
" \"longitude\": -1.46616,\n" +
" \"latitude\": 53.38227,\n" +
" \"distance\": 80\n" +
" }\n" +
"]\n" +
"}";
JsonParser jsonParser = new JsonParser();
JsonElement element = jsonParser.parse(json);
List<String> longitudes = new ArrayList<>();
List<String> latitudes = new ArrayList<>();
if (element.isJsonObject()) {
JsonObject bus = element . getAsJsonObject ();
JsonArray array = bus.getAsJsonArray("stops");
array.forEach(jsonElement -> {
extractToList(longitudes, (JsonObject) jsonElement, "longitude");
extractToList(latitudes, (JsonObject) jsonElement, "latitude");
});
}
System.out.println(longitudes);
System.out.println(latitudes);
}
private static void extractToList(List<String> list, JsonObject jsonElement, String field) {
final JsonElement longitude = jsonElement.get(field);
if(longitude != null) {
list.add(longitude.getAsString());
}
}
If you run this you get printed out on the console:
[-1.46616, -1.46583, -1.46616]
[53.38248, 53.38228, 53.38227]
I have assumed you are using Google's GSON library.
Instead of
longitudes.add(array.get(i)).get("longitude");
latitudes.add(array.get(i)).get("latitude");
Use
longitudes.add(array.get(i).get("longitude").getAsString());
latitudes.add(array.get(i).get("latitude").getAsString());
Related
The goal is replace a value in a nested JSON.
Original JSON :
{
"data": {
"car": {
"xia": [
"a0.c904.b0"
]
}
}
}
Expected JSON:
{
"data": {
"car": {
"xia": [
"a0.c234.b0"
]
}
}
}
My code below gives me the JSONElement but I don't know how to put it back to the json object?
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
String inputJson = "{\n"
+ " \"data\": {\n"
+ " \"car\": {\n"
+ " \"xia\": [\n"
+ " \"a0.c904.b0\"\n"
+ " ]\n"
+ " }\n"
+ " }\n"
+ "}";
JsonObject jsonObject = new JsonParser().parse(inputJson).getAsJsonObject();
JsonElement jsonElement = jsonObject.get("data").getAsJsonObject().get("car").getAsJsonObject().get("xia");
String str = jsonElement.getAsString();
System.out.println(str);
String[] strs = str.split("\\.");
String replaced = strs[0] + "." + strs[1].replaceAll("\\d+", "234") + "." + strs[2];
System.out.println(replaced);
JsonElement jsonElementReplaced = new JsonParser().parse(replaced);
I just had to do :
jsonObject.get("data").getAsJsonObject().get("car").getAsJsonObject().add("xia", jsonElementReplaced);
I'd like to display values from my JSON just for testing purposes, but I've received literally nothing. Where can be an issue? The link in Utils is correctly for sure, I've runned it on my browser, and everything was good.
Here's the code
Utils class
public class WeatherUtils {
public WeatherUtils(){}
public static ArrayList<Weather> getHourlyData (double minTemp, double maxTemp, double currentTemp, double airPressure){
ArrayList<Weather> weatherList = new ArrayList<>();
try {
JSONObject reader = new JSONObject("https://api.openweathermap.org/data/2.5/forecast?q=London,us&units=metric&appid=ID...");
JSONArray array = reader.getJSONArray("list");
for (int i = 0; i<array.length(); i++){
JSONObject secondReader = array.getJSONObject(i);
JSONObject dataObject = secondReader.getJSONObject("main");
for (int j = 0; j<dataObject.length(); j++){
currentTemp = dataObject.getDouble("temp");
minTemp = dataObject.getDouble("temp_min");
maxTemp = dataObject.getDouble("temp_max");
airPressure = dataObject.getDouble("pressure");
}
weatherList.add(new Weather(currentTemp,minTemp,maxTemp,airPressure));
}
} catch (JSONException e) {
e.printStackTrace();
}
return weatherList;
}
}
MainActivity
Double a,b,c,d;
a = 0.0;
b = 0.0;
c = 0.0;
d = 0.0;
ArrayList<Weather> weathers = WeatherUtils.getHourlyData(a,b,c,d);
System.out.println(weathers);
JSON structure
{
"cod": "200",
"message": 0.0074,
"cnt": 40,
"list": [
{
"dt": 1559131200,
"main": {
"temp": 22.1,
"temp_min": 21.32,
"temp_max": 22.1,
"pressure": 1012.31,
"sea_level": 1012.31,
"grnd_level": 976.84,
"humidity": 92,
"temp_kf": 0.78
},
"weather": [
{
"id": 500,
"main": "Rain",
"description": "light rain",
"icon": "10d"
}
],
"clouds": {
"all": 89
},
"wind": {
"speed": 3.08,
"deg": 213.025
},
"rain": {
"3h": 0.875
},
"sys": {
"pod": "d"
},
"dt_txt": "2019-05-29 12:00:00"
},
{
Of course, there are more data. I've posted one "block"
How I may fix that?
Well, given that you just want to "test" the json parsing, you have few options but let's go with a simple one. But first, I would say to extract the parser and put it in its own class/method so it becomes easier to test, something like this:
public class WeatherUtils {
public WeatherUtils(){}
public static ArrayList<Weather> getHourlyData (double minTemp, double maxTemp, double currentTemp, double airPressure){
final ArrayList<Weather> weatherList = new ArrayList<>();
try {
final JSONObject response = httpCall();
weatherList = mapWeatherResponse(response);
} catch (JSONException e) {
e.printStackTrace();
}
return weatherList;
}
public static List<Weather> mapWeatherResponse(JSONObject reader){
final ArrayList<Weather> weatherList = new ArrayList<>();
JSONArray array = reader.getJSONArray("list");
for (int i = 0; i<array.length(); i++){
JSONObject secondReader = array.getJSONObject(i);
JSONObject dataObject = secondReader.getJSONObject("main");
for (int j = 0; j<dataObject.length(); j++){
currentTemp = dataObject.getDouble("temp");
minTemp = dataObject.getDouble("temp_min");
maxTemp = dataObject.getDouble("temp_max");
airPressure = dataObject.getDouble("pressure");
}
weatherList.add(new Weather(currentTemp,minTemp,maxTemp,airPressure));
}
}
}
Test the response parser with a junit test:
You can create a junit test like this:
public class WeatherUtilsTest {
#Test
public void parserResponseTEst() {
final List<String> expectedResponse = new ArrayList<>();
//fill the expectedResponse with the correspondent values
final String json = "{\n" +
" \"cod\": \"200\",\n" +
" \"message\": 0.0074,\n" +
" \"cnt\": 40,\n" +
" \"list\": [\n" +
" {\n" +
" \"dt\": 1559131200,\n" +
" \"main\": {\n" +
" \"temp\": 22.1,\n" +
" \"temp_min\": 21.32,\n" +
" \"temp_max\": 22.1,\n" +
" \"pressure\": 1012.31,\n" +
" \"sea_level\": 1012.31,\n" +
" \"grnd_level\": 976.84,\n" +
" \"humidity\": 92,\n" +
" \"temp_kf\": 0.78\n" +
" },\n" +
" \"weather\": [\n" +
" {\n" +
" \"id\": 500,\n" +
" \"main\": \"Rain\",\n" +
" \"description\": \"light rain\",\n" +
" \"icon\": \"10d\"\n" +
" }\n" +
" ],\n" +
" \"clouds\": {\n" +
" \"all\": 89\n" +
" },\n" +
" \"wind\": {\n" +
" \"speed\": 3.08,\n" +
" \"deg\": 213.025\n" +
" },\n" +
" \"rain\": {\n" +
" \"3h\": 0.875\n" +
" }\n" +
" }]\n" +
" }";
final List<String> response = WeatherUtils.mapWeatherResponse(new JSONObject(json));
assertEquals(expectedResponse, response);
}
}
There is nothing wrong with the JSONObject parser you are doing. You mentioned the link you are using in Utils is correct, do you get a proper response when you test it in your browser, postman, insomnia?
OBS JSONObject reader = new JSONObject("https://api..."); does not fetch anything, what you are doing there is creating a JSONObject from the given String, i.e. "https://....". To fetch the data you need to implement some http client. Here is an example https://stackoverflow.com/a/4457526/761668
You're not getting the response from the server, you're trying to initialize a JSONObject with the URL.
To retrieve it you should replace this line:
JSONObject reader = new JSONObject("https://api.openweathermap.org/data/2.5/forecast?q=London,us&units=metric&appid=ID...");
with this code:
HttpURLConnection conn = null;
String data = null;
try {
conn = (HttpURLConnection) new URL("https://api.openweathermap.org/data/2.5/forecast?q=London,us&units=metric&appid=ID...").openConnection();
conn.setRequestMethod("GET");
conn.connect();
BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder sb = new StringBuilder();
String line;
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
br.close();
data = sb.toString();
} catch (Exception e) {
// do something
} finally {
if (conn != null) {
try {
conn.disconnect();
} catch (Exception ex) {
// do something
}
}
}
JSONObject reader = new JSONObject(data);
This code will retrieve the JSON object from the endpoint and convert it to a String object. Then you can create a JSONObject with it.
I have this JSON:
request_time: "2018-03-13T00:59:44+00:00",
stops: [
{
atcocode: "370023715",
mode: "bus",
name: "AG1",
stop_name: "AG1",
smscode: "37023715",
bearing: "N",
locality: "Sheffield Centre",
indicator: "AG1",
longitude: -1.46616,
latitude: 53.38248,
distance: 57
},
{
atcocode: "370027281",
mode: "bus",
name: "AG12",
stop_name: "AG12",
smscode: "37027281",
bearing: "N",
locality: "Sheffield Centre",
indicator: "AG12",
longitude: -1.46583,
latitude: 53.38228,
distance: 77
}
]
}
I would like to retrieve and store each locality and atocode within this sub tree, in an array. I currently have this java code, but it only displays everything within the sub tree :
JsonParser parser = new JsonParser();
JsonElement element = parser.parse(json);
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html><body>");
if (element.isJsonObject()){
JsonObject bus = element.getAsJsonObject();
JsonArray array = bus.getAsJsonArray("stops");
for (int i = 0; i < array.size(); i++){
out.println(array.get(i));
}
So, just use get method of JsonObject on each "stops" array element:
public static void main(String[] args) {
String json = "{request_time: \"2018-03-13T00:59:44+00:00\",\n" + "stops: [\n" + "{\n"
+ "atcocode: \"370023715\",\n" + "mode: \"bus\",\n" + "name: \"AG1\",\n"
+ "stop_name: \"AG1\",\n" + "smscode: \"37023715\",\n" + "bearing: \"N\",\n"
+ "locality: \"Sheffield Centre\",\n" + "indicator: \"AG1\",\n" + "longitude: -1.46616,\n"
+ "latitude: 53.38248,\n" + "distance: 57\n" + "},\n" + "{\n" + "atcocode: \"370027281\",\n"
+ "mode: \"bus\",\n" + "name: \"AG12\",\n" + "stop_name: \"AG12\",\n"
+ "smscode: \"37027281\",\n" + "bearing: \"N\",\n" + "locality: \"Sheffield Centre\",\n"
+ "indicator: \"AG12\",\n" + "longitude: -1.46583,\n" + "latitude: 53.38228,\n"
+ "distance: 77\n" + "}\n" + "]\n" + "}";
JsonParser parser = new JsonParser();
JsonElement element = parser.parse(json);
if (element.isJsonObject()) {
JsonObject bus = element.getAsJsonObject();
JsonArray array = bus.getAsJsonArray("stops");
for (int i = 0; i < array.size(); i++) {
System.out.println(((JsonObject) array.get(i)).get("locality"));
System.out.println(((JsonObject) array.get(i)).get("atcocode"));
}
}
}
Output:
"Sheffield Centre"
"370023715"
"Sheffield Centre"
"370027281"
P.S. I don't provide the code how to store these in an array as it is unclear how you want to store it, how many arrays you want...
I want to extract elements (state,county ) from this JSON string :
I am trying to parse a JSON string in java to have the individual value printed separately. But while making the program run I get nothing.
"place": [
{
"address": {
"country_code": "fr",
"country": "France",
"state": "Normandie",
"county": "Calvados"
},
"icon": "http://nominatim.openstreetmap.org/images/mapicons/poi_boundary_administrative.p.20.png",
"importance": 0.74963706049207,
"type": "administrative",
"class": "boundary",
"display_name": "Calvados, Normandie, France",
"lon": "-0.24139500722798",
"lat": "49.09076485",
"boundingbox": [
"48.7516623",
"49.4298653",
"-1.1597713",
"0.4466332"
],
"osm_id": "7453",
"osm_type": "relation",
"licence": "Data © OpenStreetMap contributors, ODbL 1.0. http://www.openstreetmap.org/copyright",
"place_id": "158910871"
}
]
any help would be appreciated. thanks.
these is my android code :
JSONObject objectPremium = new JSONObject(String.valueOf(result));
String premium = objectPremium.getString("premium");
JSONArray jArray1 = objectPremium.getJSONArray("premium");
for(int i = 0; i < jArray1.length(); i++)
{
JSONObject object3 = jArray1.getJSONObject(i);
adresse = object3.getJSONObject("place").getJSONObject("address").getString("state");
Log.e("mylog",adresse);
}
In your JSON string, "place" is a JSONArray and its containing another JSONObject. Get "place" value as below:
// Place
JSONArray place = jsonObj.getJSONArray("place");
Get "address" value as below:
// Address
JSONObject address = place.getJSONObject(0).getJSONObject("address");
Get "countryCode", "country", "state" and "county" value as below:
String countryCode = address.getString("country_code");
String country = address.getString("country");
String state = address.getString("state");
String county = address.getString("county");
Here is the fully working code. Try this:
public void parseJson() {
// Your JOSON string
String jsonStr = "{\"place\": [\n" +
" {\n" +
" \"address\": {\n" +
" \"country_code\": \"fr\",\n" +
" \"country\": \"France\",\n" +
" \"state\": \"Normandie\",\n" +
" \"county\": \"Calvados\"\n" +
" },\n" +
" \"icon\": \"http://nominatim.openstreetmap.org/images/mapicons/poi_boundary_administrative.p.20.png\",\n" +
" \"importance\": 0.74963706049207,\n" +
" \"type\": \"administrative\",\n" +
" \"class\": \"boundary\",\n" +
" \"display_name\": \"Calvados, Normandie, France\",\n" +
" \"lon\": \"-0.24139500722798\",\n" +
" \"lat\": \"49.09076485\",\n" +
" \"boundingbox\": [\n" +
" \"48.7516623\",\n" +
" \"49.4298653\",\n" +
" \"-1.1597713\",\n" +
" \"0.4466332\"\n" +
" ],\n" +
" \"osm_id\": \"7453\",\n" +
" \"osm_type\": \"relation\",\n" +
" \"licence\": \"Data © OpenStreetMap contributors, ODbL 1.0. http://www.openstreetmap.org/copyright\",\n" +
" \"place_id\": \"158910871\"\n" +
" }\n" +
" ]}";
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Place
JSONArray place = jsonObj.getJSONArray("place");
// Address
JSONObject address = place.getJSONObject(0).getJSONObject("address");
String countryCode = address.getString("country_code");
String country = address.getString("country");
String state = address.getString("state");
String county = address.getString("county");
Log.d("SUCCESS", "State: " + state + " Country: " + country + " County: " + county);
} catch (final JSONException e) {
Log.e("FAILED", "Json parsing error: " + e.getMessage());
}
}
}
Hope this will help~
The first thing you need is to make sure you are receiving this string or not. I am assuming you are trying to fetch it from some URL.
To fetch the JSON you can use the following code snippet.
private void getJSON(final String urlWebService) {
class GetJSON extends AsyncTask<Void, Void, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
Toast.makeText(getApplicationContext(), s, Toast.LENGTH_SHORT).show();
}
#Override
protected String doInBackground(Void... voids) {
try {
URL url = new URL(urlWebService);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String json;
while ((json = bufferedReader.readLine()) != null) {
sb.append(json + "\n");
}
return sb.toString().trim();
} catch (Exception e) {
return null;
}
}
}
GetJSON getJSON = new GetJSON();
getJSON.execute();
}
You need to pass your URL to this function. And if calling this method is displaying the JSON data that you are expecting then the first part is done. You have the JSON string in onPostExecute() method.
Now you can easily parse this string if it contains a valid JSON data. But the JSON that you shown in your question does not seems a valid JSON. I guess it is only part of a big JSON file. So if you need the exact code to parse your JSON post the full JSON.
Pat parsing is very easy. If the json you have is an object create an instance of JSONObject if it is an array create an instance of JSONObject.
Then you can easily get the keys if it is an object. Or you can traverse through items if it is an array.
For more details you can check this JSON Parsing in Android post.
Change for this:
JSONObject objectPremium = new JSONObject(String.valueOf(result));
String premium = objectPremium.getString("premium");
JSONArray jArray1 = objectPremium.getJSONArray("premium");
for(int i = 0; i < jArray1.length(); i++)
{
JSONObject object3 = jArray1.getJSONObject(i);
JSONArray placeArray = object3.getJSONArray("place")
JSONObject addressObject = placeArray.getJSONObject("address");
adress = addressObject.getString("state");
Log.e("mylog",adresse);
}
If your initial part of the JSON Parsing code is correct, then this should work!
JSONArray jArray = new JSONArray(result);
JSONObject objectPremium = jArray.get(0);
JSONObject json = jsonObject.getJSONObject("address");
String state = json.getString("state");
String country = json.getString("country");
Check this code,
this is how you parse and store in a list
String jsonStr = //your json string
HashMap<String, String> addressList= new HashMap<>();
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
JSONArray address = jsonObj.getJSONArray("address"); // for the address
// looping through All that
for (int i = 0; i < address.length(); i++) {
JSONObject c = address.getJSONObject(i);
String country_code= c.getString("country_code");
String country= c.getString("country");
String state= c.getString("state");
String county = c.getString("county");
// adding each child node to HashMap key => value
address.put("country_code", country_code);
address.put("country", country);
address.put("state", state);
address.put("county", county);
// adding address to address list
addressList.add(address);
}
} catch (final JSONException e) {
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Json parsing error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
});
}
HOw would I go about parsing JSON using the google GSON library? An example of my returned JSON is:
[
{
"title": "Down",
"album": "Down",
"length": 212.61,
"artist": "Jay Sean"
},
{
"title": "Come to Me (Peace)",
"album": "Growing Pains",
"length": 301.844,
"artist": "Mary J Blige"
}
]
This is an array of json objects, is that right? How would I go about extracting this with Gson? This is what im trying but am getting null pointer exceptions:
JsonElement jelement = new JsonParser().parse(jsonInfo);
JsonObject jobject = jelement.getAsJsonObject();
jobject = jobject.getAsJsonObject("");
JsonArray jarray = jobject.getAsJsonArray("");
jobject = jarray.get(0).getAsJsonObject();
String result = jobject.get("title").toString();
You must create a Type instance for List.
class MyObj {
String title;
String album;
double length;
String artist;
}
String json = "[\n" +
" {\n" +
" \"title\": \"Down\",\n" +
" \"album\": \"Down\",\n" +
" \"length\": 212.61,\n" +
" \"artist\": \"Jay Sean\"\n" +
" },\n" +
" {\n" +
" \"title\": \"Come to Me (Peace)\",\n" +
" \"album\": \"Growing Pains\",\n" +
" \"length\": 301.844,\n" +
" \"artist\": \"Mary J Blige\"\n" +
" }\n" +
"]";
Type listType = new TypeToken<List<MyObj>>() {}.getType();
List<MyObj> list = new Gson().fromJson(json, listType);
System.out.println(new Gson().toJson(list));
Gson gson = new Gson();
gson. //a lot methods