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Create org.json.JSONObject from a class object by using Gson

I have the following Java class
public static class LogItem {
public Long timestamp;
public Integer level;
public String topic;
public String type;
public String message;
}
and I want to convert an ArrayList<LogItem> into the following JSON string:
{"logitems":[
{"timestamp":1560924642000, "level":20, "topic":"websocket", "type":"status", "message":"connected (mobile)"},
...
]}`
I would like to do the following:
JSONArray logitems = new JSONArray();
for (DB_LogUtils.LogItem item : items) {
logitems.put(DB_LogUtils.asJSONObject(item)); // <----
}
JSONObject data = new JSONObject();
data.put("logitems", logitems);
webViewFragment.onInjectMessage(data.toString(), null);
where DB_LogUtils.asJSONObject is the following method
public static JSONObject asJSONObject(LogItem item) throws JSONException
{
JSONObject logitem = new JSONObject();
logitem.put("timestamp", item.timestamp);
logitem.put("level", item.level);
logitem.put("topic", item.topic);
logitem.put("type", item.type);
logitem.put("message", item.message);
return logitem;
}
but instead of doing this manually (like logitem.put("timestamp", item.timestamp);) I want to do this with Gson, so that I would end up with something like this
JSONArray logitems = new JSONArray();
for (DB_LogUtils.LogItem item : items) {
logitems.put(new Gson().toJSONObject(item)); // <----
}
JSONObject data = new JSONObject();
data.put("logitems", logitems);
webViewFragment.onInjectMessage(data.toString(), null);
in order to not have to edit the code at multiple points when the LogItem class changes.
But Gson().toJSONObject(...) does not exist, only Gson().toJson(...), which returns a String. I don't want to transition into a String only to then parse it with org.json.JSONObject.
I ended up using a second class
public static class LogItems {
public List<LogItem> logitems = new ArrayList<>();
}
which then let me change the whole code to
webViewFragment.onInjectMessage(new Gson().toJson(items), null);
where items would be of type LogItems.
In this case, creating the extra wrapper class was an overall benefit, but I'd still want to know how I can create such a JSONObject from a class by using Gson.

As far as i know it could be not possible without using for loop to iterate json string into array and store into map with same key.
But you can achieve your solution instead of passing dto pass the list of items into gson object as follow.
List<Object> list = new ArrayList<Object>();
list.add("1560924642000");
list.add(20);
list.add("websocket");
list.add("status");
list.add("connected (mobile)");
Gson gson = new Gson();
Map mp = new HashMap();
mp.put("ietams", list);
String json = gson.toJson(mp);
System.out.println(json);
output will be
{"logitems":["1560924642000",20,"websocket","status","connected (mobile)"]}
Hope this will help !

How to pull values from a json object that looks like "key":[10,12,56] with Java

In wordpress an Api I use returns the tags' ids in an odd way, it returns in this ways:
"tags":[50,51,54]
I have never seen any Json that doesn't look like "key":"value", and I got no clue how to parse it...
I hope you can help, Thank you!
Update:
My bad, the example I posted was not a full json, it looks like that:
{"categories":[2,8],"tags":[50,51,54]}

The [] indicate that the tags are stored as an array. You can use JSONObject.getJSONArray() to access the array as a JSONArray object, then use .getInt() to retrieve the values. For example:
String jsonString = "{\"categories\":[2,8],\"tags\":[50,51,54]}";
JSONObject jsonObject = new JSONObject(jsonString);
JSONArray tagsArray = jsonObject.getJSONArray("tags");
// Transfer JSONArray to an int[] array.
int tags[] = new int[tagsArray.length()];
for (int i=0; i<tagsArray.length(); i++) {
tags[i] = tagsArray.getInt(i);
}

You can create a class for this json string and parse the json with just one line of code as shown in main method.
public class Example {
private List<Integer> categories = null;
private List<Integer> tags = null;
public List<Integer> getCategories() {
return categories;
}
public void setCategories(List<Integer> categories) {
this.categories = categories;
}
public List<Integer> getTags() {
return tags;
}
public void setTags(List<Integer> tags) {
this.tags = tags;
}
public static void main(String[] args) {
String str = "{\"categories\":[2,8],\"tags\":[50,51,54]}";
Example example = new Gson().fromJson(str, Example.class);
System.out.println(example.getCategories());
System.out.println(example.getTags());
}
}
You need to have gson library for this and have this import,
import com.google.gson.Gson;
Hope this works for you.

De/Serialize Gson an array of arrays [duplicate]

I'm trying to parse some JSON data using gson in Java that has the following structure but by looking at examples online, I cannot find anything that does the job.
Would anyone be able to assist?
{
"data":{
"id":[
{
"stuff":{
},
"values":[
[
123,
456
],
[
123,
456
],
[
123,
456
],
],
"otherStuff":"blah"
}
]
}
}

You just need to create a Java class structure that represents the data in your JSON. In order to do that, I suggest you to copy your JSON into this online JSON Viewer and you'll see the structure of your JSON much clearer...
Basically you need these classes (pseudo-code):
class Response
Data data
class Data
List<ID> id
class ID
Stuff stuff
List<List<Integer>> values
String otherStuff
Note that attribute names in your classes must match the names of your JSON fields! You may add more attributes and classes according to your actual JSON structure... Also note that you need getters and setters for all your attributes!
Finally, you just need to parse the JSON into your Java class structure with:
Gson gson = new Gson();
Response response = gson.fromJson(yourJsonString, Response.class);
And that's it! Now you can access all your data within the response object using the getters and setters...
For example, in order to access the first value 456, you'll need to do:
int value = response.getData().getId().get(0).getValues().get(0).get(1);

Depending on what you are trying to do. You could just setup a POJO heirarchy that matches your json as seen here (Preferred method). Or, you could provide a custom deserializer. I only dealt with the id data as I assumed it was the tricky implementation in question. Just step through the json using the gson types, and build up the data you are trying to represent. The Data and Id classes are just pojos composed of and reflecting the properties in the original json string.
public class MyDeserializer implements JsonDeserializer<Data>
{
#Override
public Data deserialize(JsonElement je, Type type, JsonDeserializationContext jdc) throws JsonParseException
{
final Gson gson = new Gson();
final JsonObject obj = je.getAsJsonObject(); //our original full json string
final JsonElement dataElement = obj.get("data");
final JsonElement idElement = dataElement.getAsJsonObject().get("id");
final JsonArray idArray = idElement.getAsJsonArray();
final List<Id> parsedData = new ArrayList<>();
for (Object object : idArray)
{
final JsonObject jsonObject = (JsonObject) object;
//can pass this into constructor of Id or through a setter
final JsonObject stuff = jsonObject.get("stuff").getAsJsonObject();
final JsonArray valuesArray = jsonObject.getAsJsonArray("values");
final Id id = new Id();
for (Object value : valuesArray)
{
final JsonArray nestedArray = (JsonArray)value;
final Integer[] nest = gson.fromJson(nestedArray, Integer[].class);
id.addNestedValues(nest);
}
parsedData.add(id);
}
return new Data(parsedData);
}
}
Test:
#Test
public void testMethod1()
{
final String values = "[[123, 456], [987, 654]]";
final String id = "[ {stuff: { }, values: " + values + ", otherstuff: 'stuff2' }]";
final String jsonString = "{data: {id:" + id + "}}";
System.out.println(jsonString);
final Gson gson = new GsonBuilder().registerTypeAdapter(Data.class, new MyDeserializer()).create();
System.out.println(gson.fromJson(jsonString, Data.class));
}
Result:
Data{ids=[Id {nestedList=[[123, 456], [987, 654]]}]}
POJO:
public class Data
{
private List<Id> ids;
public Data(List<Id> ids)
{
this.ids = ids;
}
#Override
public String toString()
{
return "Data{" + "ids=" + ids + '}';
}
}
public class Id
{
private List<Integer[]> nestedList;
public Id()
{
nestedList = new ArrayList<>();
}
public void addNestedValues(final Integer[] values)
{
nestedList.add(values);
}
#Override
public String toString()
{
final List<String> formattedOutput = new ArrayList();
for (Integer[] integers : nestedList)
{
formattedOutput.add(Arrays.asList(integers).toString());
}
return "Id {" + "nestedList=" + formattedOutput + '}';
}
}

Parsing JSON Object with no identifier with Jackson

I am getting JSON from a web service, the JSON response I'm getting is:
{
"response":"itemList",
"items":[
"0300300000",
"0522400317",
"1224200035",
"1224200037",
"1547409999"
]
}
I am looking to get each id within the items array. The problem is I'm unsure how to parse this with Jackson when there are no identifiers for the id in the items array. My understanding is I could have an item class with a variable id and #JsonProperty ("id"), but I don't know how to proceed. I need to display these ids in a list (which I can do no problem once I have the data.
Could someone please point me in the right direction.
Thank you.

You could deserialize into something like
public class MyData {
public String response;
public List<String> items;
}
(this will also work if you have private fields with public set methods). Or if you don't mind having jackson-specific annotations in your data classes, you can leave them as non-public and annotate them:
public class MyData {
#JsonProperty
String response;
#JsonProperty
List<String> items;
}
either way, use this to parse:
import com.fasterxml.jackson.databind.ObjectMapper;
//...
MyData data=new ObjectMapper().readValue(jsonStringFromWebService, MyData.class);

You can Convert the JSON String to JSON object, and identify the array and get the IDs..
String josn = "{\"response\":\"itemList\", \"items\":[\"0300300000\",\"0522400317\",\"1224200035\",\"1224200037\",\"1547409999\"]}";
JSONObject jsonObject = new org.json.JSONObject(josn);
JSONArray itemsArray = jsonObject.getJSONArray("items");
System.out.println("Item - 1 =" + itemsArray.getString(0));

class Something {
public String response;
#JsonCreator
public Something(#JsonProperty("response") String response) {
this.response=response;
}
public List<String> items= new ArrayList<String>();
public List<String> addItem(String item) {
items.add(item);
return items;
}
}
and then:
public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {
String json = "{\"response\":\"itemList\",\"items\":[\"0300300000\",\"0522400317\"]}";
ObjectMapper mapper = new ObjectMapper();
mapper.readValue(json, Something.class);
}

I think so, you want this :
ArrayList<String> notifArray=new ArrayList<String>();
JSONObject jsonObj= new JSONObject (resultLine);
JSONArray jArray = jsonObj.getJSONArray("items");
for (int i = 0; i < jArray.length(); i++) {
String str = jArray.getString(i);
notifArray.add(str);
}

How to parse json data using in java

I am getting this data from server how to parse this data in java .
LabelField jsonResult = new LabelField(connectJson.response);
"[{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"}]"
I am getting response in jsonResult variable

You can use libraries like Jackson to do the same. There is also Google's GSON which will help you do the same. See this example

Take a look at the JSONParser Object in this Tutorial

If you are using Eclipse plugin than may JSON library included in you SDK.
Use below code to parse your JSON string got from the server.
String test = "[{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"},{\"screen_refresh_interval\":4,\"station_list_last_update\":\"update4\"}]";
JSONArray array = new JSONArray(test);
JSONObject obj = (JSONObject) array.get(0);
Your String look like you got JSON Array from the server.
First convert your Json string to JSON Array by
JSONArray array = new JSONArray(Your JSON String);
Each element in array represent JSON Object.You can read JSON Object by
JSONObject obj = (JSONObject) array.get(Index);
You can read parameter from Object to any String variable by :
String valueStr = obj.getString("screen_refresh_interval");
May this help you.

Design a class (viz CustomClass) first with screen_refresh_interval and station_list_last_update as properties. And Make a collection class for CustomClass
I'm using Gson as deserializer. Other libraries are also available.
public class Container {
private CustomClass[] classes;
public CustomClass[] getClasses() {
return classes;
}
public void setClasses(CustomClass[] classes) {
this.classes = classes;
}
}
public class CustomClass {
private String screen_refresh_interval;
private String station_list_last_update;
public String getScreen_refresh_interval() {
return screen_refresh_interval;
}
public void setScreen_refresh_interval(String screen_refresh_interval) {
this.screen_refresh_interval = screen_refresh_interval;
}
public String getStation_list_last_update() {
return station_list_last_update;
}
public void setStation_list_last_update(String station_list_last_update) {
this.station_list_last_update = station_list_last_update;
}
}
Gson gson = new Gson();
Container customClassCollection = gson.fromJson(jsonResult, Container.class);