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Unable to deserialize HATEOS JSON using RestTemplate

I am trying to call a Spring Cloud Data Flow REST Endpoint which is supposed to return a list of all the executions of a task whose name is passed in the input.
For starters, I ran the following URL in the browser :
http://dataflow-server.myhost.net/tasks/executions?task1225
The following JSON is shown on the browser :
{
"_embedded": {
"taskExecutionResourceList": [
{
"executionId": 2908,
"exitCode": 0,
"taskName": "task1225",
"startTime": "2021-06-25T18:40:24.823+0000",
"endTime": "2021-06-25T18:40:27.585+0000",
"exitMessage": null,
"arguments": [
"--spring.datasource.username=******",
"--spring.cloud.task.name=task1225",
"--spring.datasource.url=******",
"--spring.datasource.driverClassName=org.h2.Driver",
"key=******",
"batchId=20210625_025755702",
"--spring.cloud.data.flow.platformname=default",
"--spring.cloud.task.executionid=2908"
],
"jobExecutionIds": [],
"errorMessage": null,
"externalExecutionId": "task1225-kp7mvwkmll",
"parentExecutionId": null,
"resourceUrl": "Docker Resource [docker:internal.artifactrepository.myhost.net/myProject/myimage:0.1]",
"appProperties": {
"spring.datasource.username": "******",
"spring.cloud.task.name": "task1225",
"spring.datasource.url": "******",
"spring.datasource.driverClassName": "org.h2.Driver"
},
"deploymentProperties": {
"spring.cloud.deployer.kubernetes.requests.memory": "512Mi",
"spring.cloud.deployer.kubernetes.limits.cpu": "1000m",
"spring.cloud.deployer.kubernetes.limits.memory": "8192Mi",
"spring.cloud.deployer.kubernetes.requests.cpu": "100m"
},
"taskExecutionStatus": "COMPLETE",
"_links": {
"self": {
"href": "http://dataflow-server.myhost.net/tasks/executions/2908"
}
}
}
]
},
"_links": {
"first": {
"href": "http://dataflow-server.myhost.net/tasks/executions?page=0&size=20"
},
"self": {
"href": "http://dataflow-server.myhost.net/tasks/executions?page=0&size=20"
},
"next": {
"href": "http://dataflow-server.myhost.net/tasks/executions?page=1&size=20"
},
"last": {
"href": "http://dataflow-server.myhost.net/tasks/executions?page=145&size=20"
}
},
"page": {
"size": 20,
"totalElements": 2908,
"totalPages": 146,
"number": 0
}
}
Next, I tried to call the same REST endpoint through Java; however, no matter what I try, the response object seems to be empty with none of the attributes populated :
Approach 1 : Custom domain classes created to deserialize the response. (Did not work. Empty content recieved in response)
ParameterizedTypeReference<Resources<TaskExecutions>> ptr = new ParameterizedTypeReference<Resources<TaskExecutions>>() {
};
ResponseEntity<Resources<TaskExecutions>> entity = restTemplate.exchange(
"http://dataflow-server.myhost.net/tasks/executions?task1225",
HttpMethod.GET, null, ptr);
System.out.println(entity.getBody().getContent()); **//empty content**
Where, TaskExecutions domain is as follows :
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({ "taskExecutionResourceList" })
#JsonIgnoreProperties(ignoreUnknown = true)
public class TaskExecutions {
public TaskExecutions() {
}
#JsonProperty("taskExecutionResourceList")
List<TaskExecutionResource> taskExecutionResourceList = new ArrayList<>();
#JsonProperty("taskExecutionResourceList")
public List<TaskExecutionResource> getTaskExecutionResourceList() {
return taskExecutionResourceList;
}
#JsonProperty("taskExecutionResourceList")
public void setTaskExecutionResourceList(List<TaskExecutionResource> taskExecutionResourceList) {
this.taskExecutionResourceList = taskExecutionResourceList;
}
}
And TaskExecutionResource is as follows :
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({
"executionId",
"exitCode",
"taskName",
"startTime",
"endTime",
"exitMessage",
"arguments",
"jobExecutionIds",
"errorMessage",
"externalExecutionId",
"parentExecutionId",
"resourceUrl",
"appProperties",
"deploymentProperties",
"taskExecutionStatus",
"_links" })
#JsonIgnoreProperties(ignoreUnknown = true)
public class TaskExecutionResource {
#JsonProperty("executionId")
private Integer executionId;
#JsonProperty("exitCode")
private Integer exitCode;
#JsonProperty("taskName")
private String taskName;
#JsonProperty("startTime")
private String startTime;
#JsonProperty("endTime")
private String endTime;
#JsonProperty("exitMessage")
private Object exitMessage;
#JsonProperty("arguments")
private List<String> arguments = new ArrayList<String>();
#JsonProperty("jobExecutionIds")
private List<Object> jobExecutionIds = new ArrayList<Object>();
#JsonProperty("errorMessage")
private Object errorMessage;
#JsonProperty("externalExecutionId")
private String externalExecutionId;
#JsonProperty("parentExecutionId")
private Object parentExecutionId;
#JsonProperty("resourceUrl")
private String resourceUrl;
#JsonProperty("appProperties")
private AppProperties appProperties;
#JsonProperty("deploymentProperties")
private DeploymentProperties deploymentProperties;
#JsonProperty("taskExecutionStatus")
private String taskExecutionStatus;
#JsonProperty("_links")
private Links links;
#JsonProperty("executionId")
public Integer getExecutionId() {
return executionId;
}
#JsonProperty("executionId")
public void setExecutionId(Integer executionId) {
this.executionId = executionId;
}
#JsonProperty("exitCode")
public Integer getExitCode() {
return exitCode;
}
#JsonProperty("exitCode")
public void setExitCode(Integer exitCode) {
this.exitCode = exitCode;
}
#JsonProperty("taskName")
public String getTaskName() {
return taskName;
}
#JsonProperty("taskName")
public void setTaskName(String taskName) {
this.taskName = taskName;
}
#JsonProperty("startTime")
public String getStartTime() {
return startTime;
}
#JsonProperty("startTime")
public void setStartTime(String startTime) {
this.startTime = startTime;
}
#JsonProperty("endTime")
public String getEndTime() {
return endTime;
}
#JsonProperty("endTime")
public void setEndTime(String endTime) {
this.endTime = endTime;
}
#JsonProperty("exitMessage")
public Object getExitMessage() {
return exitMessage;
}
#JsonProperty("exitMessage")
public void setExitMessage(Object exitMessage) {
this.exitMessage = exitMessage;
}
#JsonProperty("arguments")
public List<String> getArguments() {
return arguments;
}
#JsonProperty("arguments")
public void setArguments(List<String> arguments) {
this.arguments = arguments;
}
#JsonProperty("jobExecutionIds")
public List<Object> getJobExecutionIds() {
return jobExecutionIds;
}
#JsonProperty("jobExecutionIds")
public void setJobExecutionIds(List<Object> jobExecutionIds) {
this.jobExecutionIds = jobExecutionIds;
}
#JsonProperty("errorMessage")
public Object getErrorMessage() {
return errorMessage;
}
#JsonProperty("errorMessage")
public void setErrorMessage(Object errorMessage) {
this.errorMessage = errorMessage;
}
#JsonProperty("externalExecutionId")
public String getExternalExecutionId() {
return externalExecutionId;
}
#JsonProperty("externalExecutionId")
public void setExternalExecutionId(String externalExecutionId) {
this.externalExecutionId = externalExecutionId;
}
#JsonProperty("parentExecutionId")
public Object getParentExecutionId() {
return parentExecutionId;
}
#JsonProperty("parentExecutionId")
public void setParentExecutionId(Object parentExecutionId) {
this.parentExecutionId = parentExecutionId;
}
#JsonProperty("resourceUrl")
public String getResourceUrl() {
return resourceUrl;
}
#JsonProperty("resourceUrl")
public void setResourceUrl(String resourceUrl) {
this.resourceUrl = resourceUrl;
}
#JsonProperty("appProperties")
public AppProperties getAppProperties() {
return appProperties;
}
#JsonProperty("appProperties")
public void setAppProperties(AppProperties appProperties) {
this.appProperties = appProperties;
}
#JsonProperty("deploymentProperties")
public DeploymentProperties getDeploymentProperties() {
return deploymentProperties;
}
#JsonProperty("deploymentProperties")
public void setDeploymentProperties(DeploymentProperties deploymentProperties) {
this.deploymentProperties = deploymentProperties;
}
#JsonProperty("taskExecutionStatus")
public String getTaskExecutionStatus() {
return taskExecutionStatus;
}
#JsonProperty("taskExecutionStatus")
public void setTaskExecutionStatus(String taskExecutionStatus) {
this.taskExecutionStatus = taskExecutionStatus;
}
#JsonProperty("_links")
public Links getLinks() {
return links;
}
#JsonProperty("_links")
public void setLinks(Links links) {
this.links = links;
}
}
Approach 2 : Add spring-cloud-data-flow-rest as a maven dependency in my project and use the TaskExectuionResource entity defined in this project. :
TaskExecutionResource.Page = restTemplate.getForObject("http://dataflow-server.myhost.net/tasks/executions?task1225",
TaskExecutionResource.Page.class);//**Empty content**
Question : How can I deserialize the response of the JSON returned by a rest enndpoint that is using HATEOAS? It seems like a very daunting task to get this to work.

Not sure how you constructed RestTemplate but it doesn't work as is with hateoas and there's some additional steps you need to do.
To get idea what we've done see ObjectMapper config. There's hal module and additional mixin's what mapper needs to be aware of for these things to work.

Storing JSON array in different lists or arrays

{
"status": true,
"message": [
{
"ID": 1,
"TFrom": "b",
"TTo": "c"
},
{
"ID": 2,
"TFrom": "b",
"TTo": "c"
},
{
"ID": 3,
"TFrom": "b",
"TTo": "c"
}
]
}
This is my JSON result, I'm using Android/Java and what I want is to get each object in the "message" array separated in an array, because each one of them should be in a list item.
Which means my ListView is going to view the "message" content in lists.
It's more like this:
list1= [{"ID": 1, "TFrom": "b", "TTo": "c"}]
list2= [{"ID": 2, "TFrom": "b", "TTo": "c"}]

Message Object Class:
public class MessagesObject {
boolean status;
List<AMessage> message;
public List<AMessage> getMessage() {
return message;
}
public void setMessage(List<AMessage> message) {
this.message = message;
}
public boolean isStatus() {
return status;
}
public void setStatus(boolean status) {
this.status = status;
}
}
AMessage Class:
public class AMessage {
int ID;
String TFrom;
String TTo;
public int getID() {
return ID;
}
public void setID(int ID) {
this.ID = ID;
}
public String getTFrom() {
return TFrom;
}
public void setTFrom(String TFrom) {
this.TFrom = TFrom;
}
public String getTTo() {
return TTo;
}
public void setTTo(String TTo) {
this.TTo = TTo;
}
}
Usage :
String json="you json string";
MessagesObject messagesObject = new Gson().fromJson(jsonToParse, MessagesObject.class);
Ref Gson :
implementation 'com.google.code.gson:gson:2.8.2'
Output:

I'm not sure what you really want, but if you really would like to convert an array into list of arrays, ie.
[1, 2, 3] => [[1], [2], [3]]
You can use this code as a starting point.
List<List<T>> YOUR_LIST_OF_LISTS = message.stream().map((e) -> {
ArrayList<T> temp = new ArrayList<>();
temp.add(e);
return temp;
}).collect(Collectors.toList());
Replace T with some datatype you want, in your case probably JSONObject.
Not android specific, just java codes. I'm not sure why you would want to do something like this tho. Comment below if this is not what you intended.

JSONObject heroObject = data.getJSONObject("favorite");
JSONArray jarray=heroObject.getJSONArray("message");
ArrayList<HashMap<String,String>> array=new ArrayList<>();
//now looping through all the elements of the json array
for (int i = 0; i < jarray.length(); i++) {
//getting the json object of the particular index inside the array
JSONObject heroObject = jarray.getJSONObject(i);
HashMap<String,String> inner=new HashMap<String, String>();
inner.put("id", heroObject.getString("ID"));
inner.put("from", heroObject.getString("TFrom"));
inner.put("to", heroObject.getString("TTo"));
array.add(inner);
}

Use gson library. check below how to implement in project.
build.gradle
implementation 'com.google.code.gson:gson:2.7'
Then create MessageModel.java and MessageBaseModel.java.
MessageModel.java
public class MessageModel {
#SerializedName("ID")
int id;
#SerializedName("TFrom")
String tFrom;
#SerializedName("TTo")
String tTo;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String gettFrom() {
return tFrom;
}
public void settFrom(String tFrom) {
this.tFrom = tFrom;
}
public String gettTo() {
return tTo;
}
public void settTo(String tTo) {
this.tTo = tTo;
}
}
MessageBaseModel.java
public class MessageBaseModel {
#SerializedName("status")
boolean status;
#SerializedName("message")
ArrayList<MessageModel> messageModels = new ArrayList<>();
public boolean isStatus() {
return status;
}
public void setStatus(boolean status) {
this.status = status;
}
public ArrayList<MessageModel> getMessageModels() {
return messageModels;
}
public void setMessageModels(ArrayList<MessageModel> messageModels) {
this.messageModels = messageModels;
}
}
Use below code in your main activity:(note: result is your JSON result)
MessageBaseModel messageBaseModel=new Gson().fromJson(result.toString() , MessageBaseModel.class);
ArrayList<MessageModel> messageModels = MessageBaseModel.getMessageModels();
Check below example to get the output:
messageModels.get(0) is your first message object
messageModels.get(0).getId()=1
messageModels.get(0).gettFrom()=b
messageModels.get(1).getId()=2
messageModels.get(2).getId()=3
Sorry for my english.

Try this
List<Map<String,String>> list = new ArrayList<>();
try
{
JSONArray messageArray = response.getJSONArray("message");
for (int i = 0;i<messageArray.length(); i++)
{
Map<String,String> map = new HashMap<>();
JSONObject jsonObject = messageArray.getJSONObject(i);
Iterator<String> keys = jsonObject.keys();
while (keys.hasNext())
{
String key = keys.next();
String value = jsonObject.getString(key);
map.put(key,value);
}
list.add(map);
}
}
catch (JSONException e)
{
e.printStackTrace();
}

Reading a JSON file with multiple attributes

I'm trying to read a JSON file that contains an array of different bikes. When trying to print out the bikes to the java console, i keep getting a null point exception. I'm going to make it so that all the bikes are made into object, but for now just looking on how to print them out.
public static void main(String[] args) {
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(new FileReader("src/bikes.json"));
JSONObject jsonObject = (JSONObject) obj;
//System.out.println(jsonObject);
JSONArray bikeList = (JSONArray) jsonObject.get("BikeList");
Iterator<String> iterator = bikeList.iterator();
while(iterator.hasNext()) {
System.out.println(iterator.next());
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
JSON File:
{
"Search": {
"BikeList": [
{
"weight": "14.8",
"colour": "Blue",
"price": 149.99,
"name": "Hybrid Pro"
},
{
"weight": "15.8",
"colour": "Red",
"price": 249.99,
"name": "Slant comp"
},
{
"weight": "17.9",
"colour": "Pink",
"price": 500.00,
"name": "Charm"
}
]
}
}

First you have to get the "Search" object. And also you can't just print the object. You need to fetch all the attributes:
public static void main(String[] args) {
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(new FileReader("src/bikes.json"));
JSONObject jsonObject = (JSONObject) obj;
// System.out.println(jsonObject);
JSONObject search = (JSONObject) jsonObject.get("Search");
JSONArray bikeList = (JSONArray) search.get("BikeList");
for (int i = 0; i < bikeList.size(); i++) {
JSONObject bike = (JSONObject) bikeList.get(i);
System.out.println("********************");
System.out.println("Weight: " + bike.get("weight"));
System.out.println("Colour: " + bike.get("colour"));
System.out.println("Price: " + bike.get("price"));
System.out.println("Name: " + bike.get("name"));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
}

Why Don't you try this.
public static void main(String[] args) {
JSONParser parser = new JSONParser();
try {
Object obj = parser.parse(new FileReader("src/bikes.json"));
JSONObject jsonObject = (JSONObject) obj;
//System.out.println(jsonObject);
*JSONArray Search= (JSONArray) jsonObject.get("Search");
JSONArray bikeList = (JSONArray) Search.get("BikeList");*
Iterator<String> iterator = bikeList.iterator();
while(iterator.hasNext()) {
System.out.println(iterator.next());
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}

instead of
JSONArray bikeList = (JSONArray) jsonObject.get("BikeList");
you have to use the arrayBuilder like this
JsonArray array = Json.createArrayBuilder().build();
in an example:
[
{ "type": "home", "number": "212 555-1234" },
{ "type": "fax", "number": "646 555-4567" }
]
JsonArray value = Json.createArrayBuilder()
.add(Json.createObjectBuilder()
.add("type", "home")
.add("number", "212 555-1234"))
.add(Json.createObjectBuilder()
.add("type", "fax")
.add("number", "646 555-4567"))
.build();
quick info here
JsonArray
or here
How to create correct JsonArray in Java using JSONObject

Your object is null because, it does not exist. For that you need to have a schema for JSON document like this,
{
"BikeList": [
The above code contains, a first-level BikeList. Which you would then capture from the code. This is the mistake in your code. I believe, you need to read the Search node first, and then move down to the next one to capture the list,
{
"Search": { // This one first.
"BikeList": [
That way, you would first require to get the Search object, then get the BikeList, otherwise it will always be null.
// Search is an object, not an array.
JSONObject search = (JSONObject) jsonObject.get("Search");
// Find the list in the search object.
Rest of code is the one you already have. This would get the list for you.

Create java Pojos and annotate with Jackson 2
package com.example;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({ "Search" })
public class Bike {
#JsonProperty("Search")
private Search search;
/**
* No args constructor for use in serialization
*
*/
public Bike() {
}
/**
*
* #param search
*/
public Bike(final Search search) {
super();
this.search = search;
}
#JsonProperty("Search")
public Search getSearch() {
return search;
}
#JsonProperty("Search")
public void setSearch(final Search search) {
this.search = search;
}
#Override
public String toString() {
return "Bike [search=" + search + "]";
}
}
package com.example;
import java.util.List;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({ "BikeList" })
public class Search {
#JsonProperty("BikeList")
private List<BikeList> bikeList = null;
/**
* No args constructor for use in serialization
*
*/
public Search() {
}
/**
*
* #param bikeList
*/
public Search(final List<BikeList> bikeList) {
super();
this.bikeList = bikeList;
}
#JsonProperty("BikeList")
public List<BikeList> getBikeList() {
return bikeList;
}
#JsonProperty("BikeList")
public void setBikeList(final List<BikeList> bikeList) {
this.bikeList = bikeList;
}
#Override
public String toString() {
return "Search [bikeList=" + bikeList + "]";
}
}
package com.example;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({ "weight", "colour", "price", "name" })
public class BikeList {
#JsonProperty("weight")
private String weight;
#JsonProperty("colour")
private String colour;
#JsonProperty("price")
private Double price;
#JsonProperty("name")
private String name;
/**
* No args constructor for use in serialization
*
*/
public BikeList() {
}
/**
*
* #param colour
* #param price
* #param weight
* #param name
*/
public BikeList(final String weight, final String colour, final Double price, final String name) {
super();
this.weight = weight;
this.colour = colour;
this.price = price;
this.name = name;
}
#JsonProperty("weight")
public String getWeight() {
return weight;
}
#JsonProperty("weight")
public void setWeight(final String weight) {
this.weight = weight;
}
#JsonProperty("colour")
public String getColour() {
return colour;
}
#JsonProperty("colour")
public void setColour(final String colour) {
this.colour = colour;
}
#JsonProperty("price")
public Double getPrice() {
return price;
}
#JsonProperty("price")
public void setPrice(final Double price) {
this.price = price;
}
#JsonProperty("name")
public String getName() {
return name;
}
#JsonProperty("name")
public void setName(final String name) {
this.name = name;
}
#Override
public String toString() {
return "BikeList [weight=" + weight + ", colour=" + colour + ", price=" + price + ", name=" + name + "]";
}
}
Then employ Jackson to read input json and convert to Java Objects
package com.example;
import java.io.File;
import java.io.IOException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
public class Stackoverflow {
private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
private static final ObjectReader OBJECT_READER_BIKE = OBJECT_MAPPER.readerFor(Bike.class);
public static void main(final String[] args) throws IOException {
final Bike bike = OBJECT_READER_BIKE.readValue(new File("input/bike.json"));
System.out.println(bike);
}
}
output obtained:-
Bike [search=Search [bikeList=[BikeList [weight=14.8, colour=Blue, price=149.99, name=Hybrid Pro], BikeList [weight=15.8, colour=Red, price=249.99, name=Slant comp], BikeList [weight=17.9, colour=Pink, price=500.0, name=Charm]]]]

How to use get data using json object and display in listivew?

I have JSON like this
{
"data":
[
{
"id": 1,
"Name": "Choc Cake",
"Image": "1.jpg",
"Category": "Meal",
"Method": "",
"Ingredients":
[
{
"name": "1 Cup Ice"
},
{
"name": "1 Bag Beans"
}
]
},
{
"id": 2,
"Name": "Ice Cake",
"Image": "dfdsfdsfsdfdfdsf.jpg",
"Category": "Meal",
"Method": "",
"Ingredients":
[
{
"name": "1 Cup Ice"
}
]
}
]
}
I am using JSON Object to de-Serialize the data
this is what i am trying to
JSONObject jsonObj = new JSONObject(jsonStr);
String first = jsonObj.getJSONObject("data").getString("name");
System.out.println(first);
But a Cant seem to get the name or anything
Not sure what i am doing wrong?
and then i am trying to display it into a listview but haven't got to that part yet

data is a JSON Array, not a JSONObject
try: jsonObj.getJSONArray("data").getJSONObject(0).getString("name")
also note the difference between getString and optString, if you don't want an exception on null use the later.

First parse your Json from below method,
private ArrayList<String> getStringFromJson(String jsonStr)
{
ArrayList<String> mNames = new ArrayList<String>();
JSONArray array = new JSONArray(jsonStr);
for (int i = 0; i < array.length(); i++) {
JSONObject row = array.getJSONObject(i);
mNames= row.getString("Name");
}
return mNames;
}

try {
JSONObject jsonObj = new JSONObject(jsonStr);
jsonObj.getJSONArray("data").getJSONObject(0).getString("name")
} catch (JSONException e) {
}
Data is a json array. Use getJsonObject for json objects.
Refer to this example to create a ListView and populate it's adapter with data from a json object.

Use GSON instead JSON. Hope it helps you.
GsonBuilder gsonBuilder = new GsonBuilder();
Gson gson = gsonBuilder.create();
List<Data> datas= new ArrayList<Data>();
datas= Arrays.asList(gson.fromJson(jsonString, Data[].class));
public class Ingredients {
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
private String name;
}
public class Data {
private int id;
private String Name;
private String Image;
private String Category;
private String Method;
public List<Ingredients> getIngredients() {
return Ingredients;
}
public void setIngredients(List<Ingredients> ingredients) {
Ingredients = ingredients;
}
private List<Ingredients> Ingredients = new ArrayList<Ingredients>();
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public String getImage() {
return Image;
}
public void setImage(String image) {
Image = image;
}
public String getCategory() {
return Category;
}
public void setCategory(String category) {
Category = category;
}
public String getMethod() {
return Method;
}
public void setMethod(String method) {
Method = method;
}
}

Converting JSON to Java object using Gson

I am trying to convert JSON string to simple java object but it is returning null. Below are the class details.
JSON String:
{"menu":
{"id": "file",
"value": "File",
}
}
This is parsable class:
public static void main(String[] args) {
try {
Reader r = new
InputStreamReader(TestGson.class.getResourceAsStream("testdata.json"), "UTF-8");
String s = Helper.readAll(r);
Gson gson = new Gson();
Menu m = gson.fromJson(s, Menu.class);
System.out.println(m.getId());
System.out.println(m.getValue());
} catch (IOException e) {
e.printStackTrace();
}
}
Below are th model class:
public class Menu {
String id;
String value;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
public String toString() {
return String.format("id: %s, value: %d", id, value);
}
}
Everytime i am getting null. Can anyone please help me?

Your JSON is an object with a field menu.
If you add the same in your Java it works:
class MenuWrapper {
Menu menu;
public Menu getMenu() { return menu; }
public void setMenu(Menu m) { menu = m; }
}
And an example:
public static void main(String[] args) {
String json = "{\"menu\": {\"id\": \"file\", \"value\": \"File\"} }";
Gson gson = new Gson();
MenuWrapper m = gson.fromJson(json, MenuWrapper.class);
System.out.println(m.getMenu().getId());
System.out.println(m.getMenu().getValue());
}
It will print:
file
File
And your JSON: {"menu": {"id": "file", "value": "File", } } has an error, it has an extra comma. It should be:
{"menu": {"id": "file", "value": "File" } }

What I have found helpful with Gson is to create an an instance of the class, call toJson() on it and compare the generated string with the string I am trying to parse.