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Gson Parse Json with List<String>

I have a class with some fields:
public class GsonRepro {
class A {
private List<String> field1 = new ArrayList<>();
private String name;
private Integer status;
public A(){
}
public List<String> getfield1() { return field1; }
public void setField1(List<String> field1) { this.field1 = field1; }
public String getName() { return name; }
public void setName() { this.name = name; }
public Integer getStatus() { return status; }
public void setStatus(int status) { this.status = status; }
}
public static void main(String[] args) {
String str = "{\"name\":\"my-name-1\",\"status\":0,\"field1\":[\"0eac6b1d3d494c2d8568cd82d9d13d5f\"]}";
A a = new Gson().fromJson(str, A.class);
}
}
All fields are parsed but the List<String> field1, how can I get this to work?
Solution:
The code above works just fine. Initially, I just had a typo in the List field.

I tried with the code as above that you shared and is working fine without any issues. Please check following code and verify,
public static void main(String[] args) {
String str = "{\"name\":\"my-name-1\",\"status\":0,\"field1\":[\"0eac6b1d3d494c2d8568cd82d9d13d5f\"]}";
A a = new Gson().fromJson(str, A.class);
System.out.println(a.getName());
System.out.println(a.getStatus());
System.out.println(a.getfield1());
}
Following is the output which is being printed on console as,
my-name-1
0
[0eac6b1d3d494c2d8568cd82d9d13d5f]

you can try to use TypeToken like in this answer to another question.
For you it would look like this:
import java.lang.reflect.Type;
import com.google.gson.reflect.TypeToken;
...
Type type = new TypeToken<A>(){}.getType();
A a = new Gson().fromJson(str, type);
Greetings

import java.util.ArrayList;
import java.util.List;
import com.google.gson.Gson;
class A {
private List<String> field1 = new ArrayList<>();
private String name;
private Integer status;
public A() {
}
public List<String> getfield1() {
return field1;
}
public void setField1(List<String> field1) {
this.field1 = field1;
}
public String getName() {
return name;
}
public void setName() {
this.name = name;
}
public Integer getStatus() {
return status;
}
public void setStatus(int status) {
this.status = status;
}
}
public class GsonParseList {
public static void main(String[] args) {
String str = "{'name':'my-name-1','status':0,'field1':['0eac6b1d3d494c2','d8568cd82d9d13d5f']}";
A a = new Gson().fromJson(str, A.class);
System.out.println(a.getfield1());
}
}

Distinct the data model from ArraList to post the data to sever in android

My ArrayList is like the attached image.
So, I want to distinct the list and need to post the data to server.
So I have created the Serialized model class like
#SerializedName("VehicleList")
public List<VehicleList> vehicleList = new ArrayList<>();
public static class VehicleList {
#SerializedName("VehicleNumber")
public String vehicleNumber;
#SerializedName("Mileage")
public String mileage;
#SerializedName("Coupons")
public List<Coupons> coupons = new ArrayList<>();
}
public static class Coupons {
#SerializedName("Code")
public String code;
}
My ArrayList like this
List<CodeItem> mList = new ArrayList<CodeItem>();
code item look like this
public class CodeItem {
private String code;
private String status;
private String vehicleID;
private String mileage;
private String date;
public boolean selected;
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public String getVehicleID() {
return vehicleID;
}
public void setVehicleID(String vehicleID) {
this.vehicleID = vehicleID;
}
public String getMileage() {
return mileage;
}
public void setMileage(String mileage) {
this.mileage = mileage;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
}
Now I want to distinct the data for vehicle id and post it to sever. So how do I distinct the data by VehicleID from this mList?
Thanks in advance

Mapping JSON to Java Object return null value

I want to parsing json object like this:
{
"Count" : 1,
"Data" : [
{
"ContactID" : 1567993182,
"Email" : "enamdimensi#localhost.com",
"Action" : "unsub",
"Name" : "",
"Properties" : {}
}
],
"Total" : 1
}
to this java object.
public class Response {
#JsonProperty("Status")
private String status;
#JsonProperty("Data")
private List<DataResponse> data;
#JsonProperty("Total")
private Integer total;
#JsonProperty("Count")
private Integer count;
public MailjetResponse() {
super();
}
........ setter and getter .......
}
class DataResponse {
#JsonProperty("ContactID")
private String contactId;
#JsonProperty("Name")
private String name;
#JsonProperty("Email")
private String email;
#JsonProperty("Action")
private String action;
#JsonProperty("Properties")
private Map<String, Object> properties;
public DataResponse() {
super();
}
....... setter and getter .....
}
I used Jackson to do that, and this is my code:
final ObjectMapper mapper = new ObjectMapper();
MailjetResponse response = mapper.readValue(content, Response.class);
But, if I debug the response, all of the fields Response is null.
response [Status=null, Data=null, Total=null, Count=null]
is there something wrong with my code ?
UPDATED CODE:
Response class
public class Response {
#JsonProperty("Status")
private String status;
#JsonProperty("Data")
private List<DataResponse> data;
#JsonProperty("Total")
private Integer total;
#JsonProperty("Count")
private Integer count;
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public Integer getTotal() {
return total;
}
public void setTotal(Integer total) {
this.total = total;
}
public Integer getCount() {
return count;
}
public void setCount(Integer count) {
this.count = count;
}
#Override
public String toString() {
return "MailjetResponse [status=" + status + ", data=" + data
+ ", total=" + total + ", count=" + count + "]";
}
}
DataResponse class
public class DataResponse {
#JsonProperty("ContactID")
private String contactId;
#JsonProperty("Name")
private String name;
#JsonProperty("Email")
private String email;
#JsonProperty("Action")
private String action;
#JsonProperty("Properties")
private Map<String, Object> properties;
public String getContactID() {
return contactId;
}
public void setContactID(String contactID) {
contactId = contactID;
}
public String getName() {
return name;
}
public void setName(String name) {
name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
email = email;
}
public String getAction() {
return action;
}
public void setAction(String action) {
action = action;
}
#Override
public String toString() {
return "DataResponse [contactId=" + contactId + ", name=" + name
+ ", email=" + email + ", action=" + action + ", properties="
+ properties + "]";
}
}
There result bocome like this:
response MailjetResponse [status=null, data=[DataResponse [contactId=1567993182, name=null, email=null, action=null, properties={}]], total=1, count=1]

I have tried your example and used setter only and got email field populated after deserialisation of json.I could not see any other issue.
Below is the code I have tried :
public class Response {
#JsonProperty("Status")
private String status;
#JsonProperty("Data")
private List<DataResponse> data;
#JsonProperty("Total")
private Integer total;
#JsonProperty("Count")
private Integer count;
public void setStatus(String status) {
this.status = status;
}
public void setData(List<DataResponse> data) {
this.data = data;
}
public void setTotal(Integer total) {
this.total = total;
}
public void setCount(Integer count) {
this.count = count;
}
}
public class DataResponse {
#JsonProperty("ContactID")
private String contactId;
#JsonProperty("Name")
private String name;
#JsonProperty("Email")
private String email;
#JsonProperty("Action")
private String action;
#JsonProperty("Properties")
private Map<String, Object> properties;
public void setContactId(String contactId) {
this.contactId = contactId;
}
public void setName(String name) {
this.name = name;
}
public void setEmail(String email) {
this.email = email;
}
public void setAction(String action) {
this.action = action;
}
public void setProperties(Map<String, Object> properties) {
this.properties = properties;
}
}
final ObjectMapper mapper = new ObjectMapper();
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
final Response response = mapper.readValue(message(), Response.class);
I will prefer to Jsoncreator annotated on constructor.

Problem
The problem is in your setters.
public void setEmail(String email) {
email = email;
}
This makes an unqualified assignment fron input arg email to ... input arg email (instead of the field this.email).
It should be:
public void setEmail(String email) {
this.email = email;
}
Jackson and annotated field access
Jackson uses setters unless configured otherwise. Either correct the setters (e.g. auto-generate them with IDE) or remove them and use fields only. To do that either annotate class with
#JsonAutoDetect(fieldVisibility = Visibility.ANY, getterVisibility = Visibility.NONE, setterVisibility = Visibility.NONE)
public class DataResponse {
or change mapper settings, e.g.
ObjectMapper mapper = new ObjectMapper();
mapper.setVisibilityChecker(mapper.getSerializationConfig().getDefaultVisibilityChecker()
.withFieldVisibility(JsonAutoDetect.Visibility.ANY)
.withGetterVisibility(JsonAutoDetect.Visibility.NONE)
.withSetterVisibility(JsonAutoDetect.Visibility.NONE)
.withCreatorVisibility(JsonAutoDetect.Visibility.NONE));
Also: if you correct setters you may drop field annotations... Pick whatever is best for your use case. I prefer my jackson serialization to be done with just fields, always annotated - or with mixins.

How to extract array of json inside an attribute of type List from an object

I am using Flickr API to get the information of images and returns the following JSON:
{"photos":{"page":1,"pages":60,"perpage":100,"total":"5964","photo":[{"id":"21577339501","owner":"85277110#N02","secret":"31e850dfeb","server":"5785","farm":6,"title":"P1390956","ispublic":1,"isfriend":0,"isfamily":0}, {"id":"21577287101","owner":"85277110#N02","secret":"412990658f","server":"611","farm":1,"title":"P1400012","ispublic":1,"isfriend":0,"isfamily":0}]
I use this code in the Spring controller to deserialize the JSON:
Collection<Photos> readValues = objectMapper.readValue(new URL(url), new TypeReference<Collection<Photos>>() { });
And returns the following error:
com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
How can I solve this problem? I didn't found solutions.
Photos.class:
public class Photos {
#JsonProperty("page")
private Integer page;
#JsonProperty("pages")
private Integer pages;
#JsonProperty("perpage")
private Integer perpage;
#JsonProperty("total")
private Integer total;
#JsonProperty("photo")
#JsonDeserialize(contentAs = Photo.class, as = ArrayList.class)
private List<Photo> photo;
public Photos() {}
public Photos(Integer page, Integer pages, Integer perpage, Integer total,
List<Photo> photo) {
super();
this.page = page;
this.pages = pages;
this.perpage = perpage;
this.total = total;
this.photo = photo;
}
public Photos(List<Photo> photo) {
super();
this.photo = photo;
}
public Integer getPage() {
return page;
}
public void setPage(Integer page) {
this.page = page;
}
public Integer getPages() {
return pages;
}
public void setPages(Integer pages) {
this.pages = pages;
}
public Integer getPerpage() {
return perpage;
}
public void setPerpage(Integer perpage) {
this.perpage = perpage;
}
public Integer getTotal() {
return total;
}
public void setTotal(Integer total) {
this.total = total;
}
public List<Photo> getPhoto() {
return photo;
}
public void setPhoto(List<Photo> photo) {
this.photo = photo;
}
}
Photo.class:
public class Photo {
#JsonProperty("id")
private Integer id;
#JsonProperty("owner")
private String owner;
#JsonProperty("secret")
private String secret;
#JsonProperty("server")
private Integer server;
#JsonProperty("farm")
private Integer farm;
#JsonProperty("title")
private String title;
#JsonProperty("ispublic")
private Boolean isPublic;
#JsonProperty("isfriend")
private Boolean isFriend;
#JsonProperty("isfamily")
private Boolean isFamily;
public Photo() { }
public Photo(Integer id, String owner, String secret, Integer server,
Integer farm, String title, Boolean isPublic, Boolean isFriend,
Boolean isFamily) {
super();
this.id = id;
this.owner = owner;
this.secret = secret;
this.server = server;
this.farm = farm;
this.title = title;
this.isPublic = isPublic;
this.isFriend = isFriend;
this.isFamily = isFamily;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getOwner() {
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
public String getSecret() {
return secret;
}
public void setSecret(String secret) {
this.secret = secret;
}
public Integer getServer() {
return server;
}
public void setServer(Integer server) {
this.server = server;
}
public Integer getFarm() {
return farm;
}
public void setFarm(Integer farm) {
this.farm = farm;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public Boolean getIsPublic() {
return isPublic;
}
public void setIsPublic(Boolean isPublic) {
this.isPublic = isPublic;
}
public Boolean getIsFriend() {
return isFriend;
}
public void setIsFriend(Boolean isFriend) {
this.isFriend = isFriend;
}
public Boolean getIsFamily() {
return isFamily;
}
public void setIsFamily(Boolean isFamily) {
this.isFamily = isFamily;
}
}

The basic problem is that your json is not a Collection<Photos>, but a Map<String, Photos>, which has a single entry "photos" -> Photos instance.
I got your json to successfully deserialize by making the following changes...
A) Change the type being read:
Map<String, Photos> readValues = objectMapper.readValue(json, new TypeReference<Map<String, Photos>>() { });
Note that I read straight from a String (not a URL).
B) Change the type of Photo.id from Integer to Long, because your json has id values well exceeding max int size.
C) I added the missing two closing braces from your sample json to make it valid.
FYI, deserialization works with or without the #JsonDeserialize annotation on the List<Photo> photo field of Photos.
Here's some runnable code that works:
String json = "{\"photos\":{\"page\":1,\"pages\":60,\"perpage\":100,\"total\":\"5964\",\"photo\":[{\"id\":\"21577339501\",\"owner\":\"85277110#N02\",\"secret\":\"31e850dfeb\",\"server\":\"5785\",\"farm\":6,\"title\":\"P1390956\",\"ispublic\":1,\"isfriend\":0,\"isfamily\":0}, {\"id\":\"21577287101\",\"owner\":\"85277110#N02\",\"secret\":\"412990658f\",\"server\":\"611\",\"farm\":1,\"title\":\"P1400012\",\"ispublic\":1,\"isfriend\":0,\"isfamily\":0}]}}";
Map<String, Photos> readValues = new ObjectMapper().readValue(json, new TypeReference<Map<String, Photos>>() { });

Converting json format using java bean

I have a json string something similar
{"results":
[{"_type":"Position","_id":377078,"name":"Potsdam, Germany","type":"location","geo_position":{"latitude":52.39886,"longitude":13.06566}},
{"_type":"Position","_id":410978,"name":"Potsdam, USA","type":"location","geo_position":{"latitude":44.66978,"longitude":-74.98131}}]}
I am trying to convert to
{"results":
[{"_type":"Position","_id":377078,"name":"Potsdam, Germany","type":"location","latitude":52.39886,"longitude":13.06566},
{"_type":"Position","_id":410978,"name":"Potsdam, USA","type":"location","latitude":44.66978,"longitude":-74.98131}]}
I am converting to java and again converting back using But I am gettin null in data
SourceJSON data=new Gson().fromJson(jsonArray, SourceJSON.class);
DestinationJSON destdata = new DestinationJSON();
destdata.setLatitide(data.getGeoLocation().getLatitide());
destdata.setLongitude(data.getGeoLocation().getLongitude());
destdata.setId(data.getId());
destdata.setType(data.getType());
destdata.setName(data.getName());
destdata.set_type(data.get_type());
Gson gson = new Gson();
String json = gson.toJson(destdata);
below are my beans
public class SourceJSON implements Serializable {
private List<GEOLocation> geoLocations;
private String _type;
private String id;
private String name;
private String type;
public String get_type() {
return _type;
}
public List<GEOLocation> getGeoLocations() {
return geoLocations;
}
public void setGeoLocations(List<GEOLocation> geoLocations) {
this.geoLocations = geoLocations;
}
public void set_type(String _type) {
this._type = _type;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
}
and
public class GEOLocation implements Serializable{
private String latitide;
private String longitude;
public String getLatitide() {
return latitide;
}
public void setLatitide(String latitide) {
this.latitide = latitide;
}
public String getLongitude() {
return longitude;
}
public void setLongitude(String longitude) {
this.longitude = longitude;
}
}
and destination java
public class DestinationJSON implements Serializable {
private String _type;
private String id;
private String name;
private String type;
private String latitide;
private String longitude;
public String get_type() {
return _type;
}
public void set_type(String _type) {
this._type = _type;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getLatitide() {
return latitide;
}
public void setLatitide(String latitide) {
this.latitide = latitide;
}
public String getLongitude() {
return longitude;
}
public void setLongitude(String longitude) {
this.longitude = longitude;
}
}

All you need is this. You can try this class in your IDE with a simple copy&paste.
package stackoverflow.questions;
import java.util.*;
import com.google.gson.Gson;
public class Q20433539{
public static void main(String[] args){
String json = "{\"results\":"+
"[{\"_type\":\"Position\",\"_id\":377078,\"name\":\"Potsdam, Germany\",\"type\":\"location\",\"geo_position\":{\"latitude\":52.39886,\"longitude\":13.06566}},"+
"{\"_type\":\"Position\",\"_id\":410978,\"name\":\"Potsdam, USA\",\"type\":\"location\",\"geo_position\":{\"latitude\":44.66978,\"longitude\":-74.98131}}]}";
Gson gson = new Gson();
Map m = gson.fromJson(json, Map.class);
List<Map> innerList = (List<Map>) m.get("results");
for(Map result: innerList){
Map<String, Double> geo_position = (Map<String, Double>) result.get("geo_position");
result.put("latitude", geo_position.get("latitude"));
result.put("longitude", geo_position.get("longitude"));
result.remove("geo_position");
}
System.out.println(gson.toJson(m));
}
}
Of course, it works under the assumption that you always want to flat geo information.
Explanation: It's convenient to use POJO when working with Gson, but it's not the only way. Gson can also deseralize to Arrays/Maps if you do not specify the expected result. So I did, and then I manipulated the structure to unfold your data. After that, Gson can serialize Arrays/Maps structure again to your desidered JSON.