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How to read this json with GSON

I am trying to consume a json through an api using Google's GSON library to be able to recover the data.
I would like to be able to obtain the data of the CssValidation and Result key but it took hours and I have not been able to get it.
{
"cssvalidation": {
"uri": "https://www.mywebsite.com",
"checkedby": "http://www.w3.org/2005/07/css-validator",
"csslevel": "css3",
"date": "2021-10-17T05:07:38Z",
"timestamp": "1634490458519",
"validity": false,
"result": {
"errorcount": 7,
"warningcount": 350
}
}
}
My code in java is this:
Gson gson = new Gson();
ApiResponse apiResponse = gson.fromJson(response.body().string(), ApiResponse.class);
public class ApiResponse {
private CssValidation validation;
}
public class CssValidation{
public String uri;
public String getUri() {
return uri;
}
}

There are some problems with your json string which you need to fix before attempting to parse it, the uri value quotation is not closed, and there is an additional comma after the result object, after fixing both you end up with the functional json text
{
"cssvalidation": {
"uri": "https://www.mywebsite.com",
"checkedby": "http://www.w3.org/2005/07/css-validator",
"csslevel": "css3",
"date": "2021-10-17T05:07:38Z",
"timestamp": "1634490458519",
"validity": false,
"result": {
"errorcount": 7,
"warningcount": 350
}
}
}
you can parse it with the JsonParser and get its elements in the following way
JsonObject root = JsonParser.parseString(resp).getAsJsonObject();
JsonObject cssValidation = root.get("cssvalidation").getAsJsonObject();
String uri = cssValidation.get("uri").getAsString();
System.out.println(uri);
And you will get the following output
https://www.mywebsite.com

You seem to be doing it right, but your Java object property keys need to match up exactly with the keys in the JSON.
Specifically, the name of the property validation needs to changed to cssvalidation, so like this:
Gson gson = new Gson();
ApiResponse apiResponse = gson.fromJson(response.body().string(), ApiResponse.class);
public class ApiResponse {
private CssValidation cssvalidation;
}
public class CssValidation{
public String uri;
public String getUri() {
return uri;
}
}
Also, if the given JSON string is really what you get, then your JSON needs to be fixed, as pointed out by Lukas Ownen's answer

Java map object, which contains JSON string fields to string

I have faced problem, while mapping my object to JSON.
I have an object, which I need to convert to propper JSON, but some of my object's String fields are already in JSON format:
Sdr sdr = new Sdr();
sdr.setLocation_area(("location_area"));
sdr.setEvent_info(("{\"chargeableDur\":0}"));
sdr.setAgent_info("{\"scp\":\"NAVI\",\"stack\":\"CAP2\"}");
sdr.setService_info(("{\"bcap\":\"8090A3\",\"balID\":55969859}"));
sdr.setStarttime(("starttime"));
For JSON mapping I am using ObjectMapper:
public String toJsonString() {
ObjectMapper mapper = new ObjectMapper();
try {
return mapper.writeValueAsString(this);
} catch (JsonProcessingException e) {
logger.error(e.getMessage());
}
return toString();
}
However, ObjectMapper fails to map Strings, that already contains JSON correctly, and after mapping I get this type of JSON:
{
"event_info":""{\"chargeableDur\":0}",
"location_area":"location_area",
"agent_info":"{\"scp\":\"NAVI\",\"stack\":\"CAP2\"}",
"service_info":""{\"bcap\":\"8090A3\",\"balID\":55969859}",
"starttime":"starttime"
}
I want ObjectMapper to map my object like that:
{
"event_info":{
"chargeableDur":0
},
"location_area":"location_area",
"agent_info":{
"scp":"NAVI",
"stack":"CAP2"
},
"service_info":{
"bcap":"8090A3",
"balID":55969859
},
"starttime":"starttime"
}

Seems that your json result is stringified. Try to put the string result in separate JSONObject as
return new JSONObject(mapper.writeValueAsString(this)).toString();

How do I get data from JSON string?

Here is my code:
try {
JSONObject json = (JSONObject) new JSONTokener(result).nextValue();
System.out.println(json);
JSONObject json2 = json.getJSONObject("data");
String test = json2.getString("headline");
System.out.println(test);
} catch (JSONException e) {
e.printStackTrace();
}
My String values start with the object data. So I am trying to get that object first and then capture the the object headline inside that.
My problem is, it is not taking the object data from the string.
Once I reach the line JSONObject json2 = json.getJSONObject("data");, it throws the exception. Please shed some light on this.
"data": [
{
"headline": "Close Update"
"docSource": "MIDNIGHTTRADER",
"source": "MTClosing",
"dateTime": "2015-10-23T16:42:46-05:00",
"link": "Markets/News",
"docKey": "1413-A1067083-1B14K77PVTUM1O7PCAFMI3SJO4",
},

The value for the key data is a JSON array containing one object, and not an object itself.
To get that object inside data, replace your line that throws an exception with the following:
JSONObject json2 = json.getJSONArray("data").get(0);
This gets the data array as a JSONArray object and then gets the 0th element, which is the object you want.

Your data "object", isn't actually an object, it's an array, notice the opening square bracket... I'm assuming in your actual code, it closes with one too.
"data": [{
"headline": "Close Update"
"docSource": "MIDNIGHTTRADER",
"source": "MTClosing",
"dateTime": "2015-10-23T16:42:46-05:00",
"link": "Markets/News",
"docKey": "1413-A1067083-1B14K77PVTUM1O7PCAFMI3SJO4",
}]
Try json.getJSONArray("data")[0] instead... or whatever index you need
try {
JSONObject json = (JSONObject) new JSONTokener(result).nextValue();
System.out.println(json);
JSONObject json2 = json.getJSONArray("data")[0];
String test = json2.getString("headline");
System.out.println(test);
}
catch (JSONException e) {
e.printStackTrace();

Your problem is based on the fact that your service returns and array instead of a single json object, so from here you can follow this suggestions to process directly from the JSONArray Can't access getJSONArray in java, or, at server side you can encapsulate your response array into another object like this (java example):
public class Data<T> {
private List<T> elements;
public ObjectSugetionsDTO(){
And build the response like this:
return new ResponseEntity<Data<YourInternalRepresentation>>(
new Data<YourInternalRepresentation>(yourMethodCallForTheArray()),
HttpStatus.OK);
I have found the second way to be better at keeping my API cleaner and more readable
EDIT: Better way
I whould also suggest the use of retrofit (http://square.github.io/retrofit/), by doing so, your service calls is resumed to (Example of calling and API that retrieves a list of users):
public class UserService {
public static IUserService getUserService() {
return RestAdapterManager.createService(IUserService.class );
}
public interface IUserService{
#GET("/api/users")
public void getAllUsers(Callback<List<User>> callback);
}
}
and the service call itself
UserService.getUserService().getAllUsers(new Callback<List<User>>() {
#Override
public void success(List<User> users, Response response) {
Log.d("Exito! " , "" + users.size());
}
#Override
public void failure(RetrofitError error) {
Log.d("Fail!", error.getUrl());
}
});
The simple inicialization of the connection object
public static <S> S createService(Class<S> serviceClass, String username, String password) {
RestAdapter.Builder builder = new RestAdapter.Builder()
.setEndpoint(API_BASE_URL);//Your api base url
RestAdapter adapter = builder.setLogLevel(RestAdapter.LogLevel.FULL).build(); //change the logging level if you need to, full is TOO verbose
return adapter.create(serviceClass);
}

How do I make nested JSON Objects using Gson?

I have written a program that does some probability calculations and gives its results in the form of arrays. I want to convert these results to JSON format, but I am having issues.
I want my json object to look like this:
{
"totalSuggestions": 6,
"routes": {
"rank_2": {
"Source": "ABC",
"Weight": "0.719010390625",
"Destination": "XYZ"
},
"rank_1": {
"Source": "XYZ",
"Weight": "0.7411458281249999",
"Destination": "ABC"
},
"rank_0": {
"Source": "LMN",
"Weight": "0.994583325",
"Destination": "PQR"
}
}
}
What I understood is that I need to have an object class with the structure of my objects. For now I am experimenting with the rank object only but failing to form the required JSON.
My code for the object structure:
public class Object {
int rank_;
public class Inner{
String Source;
String Destination;
String Weightage;
}
}
I can pass either an instance of Object or an instance of Inner to toJson() method so I either get {"rank_":1} or {"Source":"ABC","Destination":"XYZ","Weightage":"123"}.
I cant seem to put each of the inner object to the corresponding rank object.
I did it with relative ease with org.json but that library has some issues with Android studio so I had to switch to Gson. What I did earlier (which worked as well) was:
public JSONObject convertToJson(int mkr, String[][] result){
JSONObject outerObj = new JSONObject();
JSONObject innerObj = new JSONObject();
JSONObject[] temp = new JSONObject[mkr];
outerObj.put("totalSuggestions", marker);
outerObj.put("routes",innerObj);
for (int i=0;i<marker;i++){
String[] useless = result[i][0].split("-");
temp[i]= new JSONObject();
temp[i].put("Source",useless[0] );
temp[i].put("Destination", useless[1]);
temp[i].put("Weight", result[i][1]);
innerObj.put("rank_"+i, temp[i]);
}
System.out.println(outerObj.toString());
return outerObj;
}

Well, first: related objects should probably be in a class together. So lets start with a simple class:
public class Results {
int mkr;
String[][] result;
}
Now we want to serialize it. We could construct a different data structure, or we could just write our own custom serializer. We want to have our custom class to allow us to use Gson's type inference for doing so, plus the code is just easier to understand. I will show you how to serialize the data structure, and I'll leave the deserialization as an exercise for you.
We create a TypeAdapter<Results>:
public class ResultsAdapter extends TypeAdapter<Results> {
public Results read(JsonReader reader) throws IOException {
if (reader.peek() == JsonToken.NULL) {
reader.nextNull();
return null;
}
// exercise for you
return results;
}
public void write(JsonWriter writer, Results value) throws IOException {
if (value == null) {
writer.nullValue();
return;
}
writer.beginObject();
writer.name("totalSuggestions").value(value.mkr);
writer.name("routes");
writer.beginObject();
for(int i = 0; i < value.mkr; i++) {
writer.name("rank_"+i);
writer.beginObject();
String[] sourceDestSplit = result[i][0].split("-");
writer.name("Source").value(sourceDestSplit[0]);
writer.name("Destination").value(sourceDestSplit[1]);
writer.name("Weight").value(result[i][1]);
writer.endObject();
}
writer.endObject();
writer.endObject();
}
}
You can then call this method by doing (note: should only create the Gson object once, but I did it this way to keep the code short):
public String convertToJson(Results results) {
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(new ResultsAdapter()):
Gson gson = builder.build();
return gson.toJson(results);
}
This will work you the way you've asked, but I strongly recommend using JSON's array syntax instead (using []). Try this instead:
public void write(JsonWriter writer, Results value) throws IOException {
if (value == null) {
writer.nullValue();
return;
}
writer.beginObject();
writer.name("totalSuggestions").value(value.mkr);
writer.name("routes");
writer.beginArray();
for(int i = 0; i < value.mkr; i++) {
writer.beginObject();
String[] sourceDestSplit = result[i][0].split("-");
writer.name("Source").value(sourceDestSplit[0]);
writer.name("Destination").value(sourceDestSplit[1]);
writer.name("Weight").value(result[i][1]);
writer.endObject();
}
writer.endArray();
writer.endObject();
}
Doing it this will will result in JSON that looks like this, which will be easier to deserialize on the other side and iterate through, because you won't have to dynamically generate maps for the keys.:
{
"totalSuggestions": 6,
"routes": [
{
"Source": "ABC",
"Weight": "0.719010390625",
"Destination": "XYZ"
},
{
"Source": "XYZ",
"Weight": "0.7411458281249999",
"Destination": "ABC"
},
{
"Source": "LMN",
"Weight": "0.994583325",
"Destination": "PQR"
}
]
}

I landed here while searching for a similar solution for the com.google.gson.JsonObject library. Now, I've found it:
JsonObject mainJson = new JsonObject();
JsonObject innerJson = new JsonObject();
innerJson.addProperty("#iot.id", "31");
mainJson.add("Datastream", innerJson); // <-- here the nesting happens
mainJson.addProperty("result", 12.3);
// fetch inner variable like this
System.out.println(mainJson.get("Datastream").getAsJsonObject().get("#iot.id").getAsString());
This works fine for me using the com.google.gson.JsonObject library.

For the record, this is what i did.
import java.util.*;
public class DataObject {
public int Suggestions;
HashMap<String, route> routes = new HashMap<>();
//constructor
public DataObject(int mkr, String[][] routesArr){
Suggestions = mkr;
{
for (int i=0;i<Suggestions;i++){
routes.put("rank_"+(i+1),new route(routesArr[i]));
}
}
}
//class to populate the hashmap
public class route{
public String Origin;
public String Destination;
public String Weight;
public route(String arr[]){
String[] splitter = arr[0].split("-");
this.Origin = splitter[0];
this.Destination = splitter[1];
this.Weight = arr[1];
}
}
}

GSON identifying JSON Object as Primitive

I am writing a relatively simple messaging app that saves its logs in the JSON format, and I am using the GSON library to parse these. I load a JSON file from a server, and put it trough Gson.toJsonTree() function. I'm not sure this is expected, but when I test the result from the previous function with the isJsonSomething() functions (isJsonObject,isJsonAray,isJsonNull,isJsonPrimitive), isJsonPrimitive returns true, and I can't parse it into a object. This is my JSON file's contents:
{
"users": [
{
"picture": "",
"type": "user",
"name": "kroltan"
}
],
"description": "No description",
"messages": [
{
"content": "something",
"time": "2013-08-30 00:38:17.212000",
"type": "message",
"author": "someone"
}
],
"type": "channel",
"name": "default"
}
And here is the class used to parse it into POJOs: (CLEANUP comments is where I've removed irrelevant code from the post)
package com.example.testapp;
//CLEANUP: All needed imports
import com.example.testapp.data.*;
import com.google.gson.*;
public class JSONConverter {
public interface JsonTypeLoadedListener {
public void onSucess(JSONType jsonType);
public void onFailure(Exception e);
}
public static final String DATE_FORMAT = "dd-MM-yyyy HH:mm:ss.SSS";
public static final HashMap<String, Class<?>> JSON_TYPES = new HashMap<String, Class<?>>();
public JSONConverter() {
JSON_TYPES.clear();
JSON_TYPES.put("channel", Channel.class);
JSON_TYPES.put("user", User.class);
JSON_TYPES.put("message", Message.class);
}
public void loadFromURL(final URL url, final JsonTypeLoadedListener listener) {
new Thread(new Runnable() {
#Override
public void run() {
JsonObject result = null;
Gson gson = new GsonBuilder().setDateFormat(DATE_FORMAT).create();
if (url.getProtocol().equals("http")) {
try {
String content = //Loads from a server, omitted for clarity
result = gson.toJsonTree(content).getAsJsonObject();
conn.disconnect();
} catch (Exception e) {
e.printStackTrace();
listener.onFailure(e);
return;
}
} else if (url.getProtocol().equals("file")) {
try {
String content = //Loads from a file, omitted for clarity
result = gson.toJsonTree(content).getAsJsonObject();
br.close();
} catch (Exception e) {
e.printStackTrace();
listener.onFailure(e);
return;
}
}
listener.onSucess((JSONType) gson.fromJson(result, JSON_TYPES.get(result.get("type").getAsString())));
}
}, "URLLoader").start();
}
public JSONType loadFromString(String s) {
Gson gson = new Gson();
JsonObject result = gson.toJsonTree(s).getAsJsonObject();
return (JSONType) gson.fromJson(result, JSON_TYPES.get(result.get("type").getAsString()));
}
}
The classes Message, User and Channel all inherit from JSONType (a custom class with a field called type and some utility methods) and contain all values present in the above mentioned JSON file.
When it reaches gson.toJsonTree(content).getAsJsonObject(), I get this error in Logcat (string omitted for clarity, it's just the full file):
java.lang.IllegalStateException: Not a JSON Object: "String containing all the file with tabs represented as \t"

I'm guessing that the tabs are causing your issue. Try to remove them with:
content = content.replaceAll("\\s","")
this will simply clean your json string from any whitespace.
Btw I suggests you to get rid of Gson library and use directly the JSONObject provided in the android sdk. You can initialize it directly with the json string, as new JSONObject(content). :)