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Parse two different API response using Retrofit 2 in Android

I am facing a problem while parsing API response using Retrofit 2.
The API's are already in production and I cannot request a change in API.
Following are two different responses I am getting from server
Success response:
{
"status":0,
"empId":121,
"message":"Data available",
"data":{
"name":"Sam",
"designation": "Software Engineer",
"mob": "1255565456"
}
}
Failure response
{
"status":10,
"empId":121,
"message":"No data available",
"data":""
}
Parsing Classes
class Response{
public int status;
public String message;
public int empId;
public Student data;
}
class Student{
public String name;
public String designation;
public String mob;
}
I am able to parse the success response. But getting the following exception for the failure case.
java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING

try this ,
Object getrow = null;
try {
getrow = this.// your object
LinkedTreeMap<Object, Object> tree = (LinkedTreeMap) getrow;
String name = tree.get(<your body>).toString()
} catch (Exception e) {
e.printStackTrace();
}

The way that you can handle this situation is by treating 'data' as a generic object rather than as a String or 'Student'.
p̶u̶b̶l̶i̶c̶ ̶S̶t̶u̶d̶e̶n̶t̶ ̶d̶a̶t̶a̶;̶
public Object data;
While Using data add a check like this
if(data instanceof String){
String parsedData=data.toString();
}else{
Student parsedData= (Student) data;
}

Make Student as an inner class or Response class. and Retrofit will parse the response and will give you the object.
class Response
{
public int status;
public String message;
public int empId;
public Student data;
Class Data
{
public String name;
public String designation;
public String mob;
}
}

Method always return empty list

I am using mvp Design pattern in android development and i am using retrofit2 with it ... when i run the function to get me information from a the web it get the information but returns null list
the Response.Body come with response that mean that the code works
the model function
List<SearchDdb> searchResult;
private Context context;
public MainModel(Context context){this.context=context;}
public List<SearchDdb> searchUser(String name) {
final MainPresenter presenter = new MainPresenter(context);
Retrofit retrofit = new Retrofit.Builder()
.baseUrl("http://jsonplaceholder.typicode.com/")
.addConverterFactory(GsonConverterFactory.create())
.build();
Db db = retrofit.create(Db.class);
Call<List<SearchDdb>> call = db.getUsers(name);
call.enqueue(new Callback<List<SearchDdb>>() {
#Override
public void onResponse(Call<List<SearchDdb>> call, Response<List<SearchDdb>> response) {
if(!response.isSuccessful()){
presenter.showDialog();
}
searchResult = response.body();
}
#Override
public void onFailure(Call<List<SearchDdb>> call, Throwable t) {
}
});
return searchResult;
}
the SearchDdb file
private int id;
private String name;
private String grade;
private String age;
private String address;
public int getId() {
return id;
}
public String getName() {
return name;
}
public String getGrade() {
return grade;
}
public String getAge() {
return age;
}
public String getAddress() {
return address;
}
}
How i call the function
List<SearchDdb> ressult = presenter.searchUser("1");

You cant call it like List<SearchDdb> ressult = presenter.searchUser("1"); because searchUser method makes an async request via retrofit. This way searchUse returns null searchResult because response has not come yet.
Define a LiveData in your viewmodel class and observe it in your activity/fragment. When response comes from api in
onResponse in searchUser post that response to live data and use it where you observe.
If you want to see a tutorial you can look at this article.
Here is another example.

java.lang.IllegalArgumentException: Illegal URL with retrofit, hostname = null

The GET request to tenants/client/{hostname} returns a json object with the property baseApiHostname.
#GET("api/tenants/client/{hostname}")
Call<HostName> getHostname(#Path("hostname") String hostname);
baseApiHostname is successful retrieved. That hostname which is used to create the rest of tenant requests from.
Log.v("base url","testing "+preferenceManager.getTenantHostname());
retrofit = new Retrofit.Builder()
.client(okHttpClient)
.addConverterFactory(GsonConverterFactory.create(builder.create()))
.baseUrl(preferenceManager.getTenantHostname())
.build();
I received the error "java.lang.IllegalArgumentException: Illegal URL".
stacktrace message
After attaching debugger I realized that hostname = null.
debugger message
Call<HostName> call = hostNameApiService.getHostname(tenant);
call.enqueue(new Callback<HostName>() {
#Override
public void onResponse(Call<HostName> call, Response<HostName> response) {
if (response.isSuccessful()) {
String hostname = response.body().getBaseApiHostname();
preferenceManager.setTenantHostname(hostname);
retrieveCampaign();
} else {
Toast.makeText(StartSurveyActivity.this, "Error Retrieving Hostname", Toast.LENGTH_SHORT).show();
}
}
Here is the Hostname model class
#SerializedName("id")
private String id;
#SerializedName("name")
private String name;
#SerializedName("baseApiHostName")
private String baseApiHostname;
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 getBaseApiHostname() {
return baseApiHostname;
}
public void setBaseApiHostname(String baseApiHostname) {
this.baseApiHostname = baseApiHostname;
}
If there's any other detail required that will aid in helping myself and other developers who may have faced a similar problem, please don't hesistate to ask.
Thanks in advance guys.

GSON is not successfully serializing any response to the field you're retrieving, so there is some misalign in how you are setting up gson to parse your json result.
Given your object and your sample JSON, your field in JSON is "baseApiHostname" whereas in your object your GSON annotation is for serialized name "baseApiHostName".

You are setting null in your Retrofit.Builder for your base URL. What is the URL for your server? You need to set that for the first time. Then you can change it after that if need be but it can't be null the first time.

How can I unwrap a specific field in a JSON using Jackson?

I have a JSON payload that looks like this:
{
"id": 32,
"name": "[Sample] Tomorrow is today, Red printed scarf",
"primary_image": {
"id": 247,
"zoom_url": "www.site.com/in_123__14581.1393831046.1280.1280.jpg",
"thumbnail_url": "www.site.com/in_123__14581.1393831046.220.290.jpg",
"standard_url": "www.site.com/in_123__14581.1393831046.386.513.jpg",
"tiny_url": "www.site.com/in_123__14581.1393831046.44.58.jpg"
}
}
Can I unwrap a specific field and discard all the others? In other words, can I bind this directly to a POJO like this:
public class Product {
private Integer id;
private String name;
private String standardUrl;
}

There are lots of ways. Do you need to deserialize, serialize or both?
One way to deserialize would be to use a creator method that takes the image as a tree node:
public static class Product {
private Integer id;
private String name;
private String standardUrl;
public Product(#JsonProperty("id") Integer id,
#JsonProperty("name") String name,
#JsonProperty("primary_image") JsonNode primaryImage) {
this.id = id;
this.name = name;
this.standardUrl = primaryImage.path("standard_url").asText();
}
}
The creator doesn't have to be a constructor, you could have a static method that is only used for Jackson deserialization.
You'd have to define a custom serializer to reserialize this, though (e.g. a StdDelegatingSerializer and a converter to wrap the string back up as an ObjectNode)

There are different ways to skin this cat, I hope you can use Jackson 2 for this, since it offers great ways to deserialize Json data, one of my favorites deserialization features is the one I'll show you here (using Builder Pattern) because allows you to validate instances when they are being constructed (or make them immutable!). For you this would look like this:
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import java.util.Map;
#JsonDeserialize(builder = Product.Builder.class)
public class Product {
private Integer id;
private String name;
private String standardUrl;
private Product(Builder builder) {
//Here you can make validations for your new instance.
this.id = builder.id;
this.name = builder.name;
//Here you have access to the primaryImage map in case you want to add new properties later.
this.standardUrl = builder.primaryImage.get("standard_url");
}
#Override
public String toString() {
return String.format("id [%d], name [%s], standardUrl [%s].", id, name, standardUrl);
}
#JsonIgnoreProperties(ignoreUnknown = true)
public static class Builder {
private Integer id;
private String name;
private Map<String, String> primaryImage;
public Builder withId(Integer id) {
this.id = id;
return this;
}
public Builder withName(String name) {
this.name = name;
return this;
}
#JsonProperty("primary_image")
public Builder withPrimaryImage(Map<String, String> primaryImage) {
this.primaryImage = primaryImage;
return this;
}
public Product build() {
return new Product(this);
}
}
}
To test it I created this class:
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
public class Test {
public static void main(String[] args) {
String serialized = "{" +
" \"id\": 32," +
" \"name\": \"[Sample] Tomorrow is today, Red printed scarf\"," +
" \"primary_image\": {" +
" \"id\": 247," +
" \"zoom_url\": \"www.site.com/in_123__14581.1393831046.1280.1280.jpg\"," +
" \"thumbnail_url\": \"www.site.com/in_123__14581.1393831046.220.290.jpg\"," +
" \"standard_url\": \"www.site.com/in_123__14581.1393831046.386.513.jpg\"," +
" \"tiny_url\": \"www.site.com/in_123__14581.1393831046.44.58.jpg\"" +
" }" +
" }";
ObjectMapper objectMapper = new ObjectMapper();
try {
Product deserialized = objectMapper.readValue(serialized, Product.class);
System.out.print(deserialized.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
The output is (using the override toString() method in Product:
id [32], name [[Sample] Tomorrow is today, Red printed scarf], standardUrl [www.site.com/in_123__14581.1393831046.386.513.jpg].

There are two ways to get the response you required. For both methods, we are going to use JsonView.
Create two types of JsonView:
public interface JViews {
public static class Public { }
public static class Product extends Public { }
}
First method
#JsonView(JViews.Public.class)
public class Product {
private Integer id;
private String name;
#JsonIgnore
private Image primaryImage;
#JsonView(JViews.Product.class)
public String getStandardUrl{
return this.primaryImage.getStandardUrl();
}
}
Second way
Using Jackson's #JsonView and #JsonUnwrapped together.
#JsonView(JViews.Public.class)
public class Product {
private Integer id;
private String name;
#JsonUnwrapped
private Image primaryImage;
}
public class Image {
private String zoomUrl;
#JsonView(JViews.Product.class)
private String standardUrl;
}
#JsonUnwrapped annotation flattens your nested object into Product object. And JsonView is used to filter accessible fields. In this case, only standardUrl field is accessible for Product view, and the result is expected to be:
{
"id": 32,
"name": "[Sample] Tomorrow is today, Red printed scarf",
"standard_url": "url"
}
If you flatten your nested object without using Views, the result will look like:
{
"id": 32,
"name": "[Sample] Tomorrow is today, Red printed scarf",
"id":1,
"standard_url": "url",
"zoom_url":"",
...
}

Jackson provided #JsonUnwrapped annotation.
See below link:
http://jackson.codehaus.org/1.9.9/javadoc/org/codehaus/jackson/annotate/JsonUnwrapped.html

JSON parsing through GSON returns null values

I am trying to read the values of a JSON output.
This is the JSON output:
{"nameOfSummoner":{"id":56529189,"name":"test","profileIconId":550,"summonerLevel":30,"revisionDate":1422110739000}}
And with the following code I am trying to read it:
final Connector connector = new Connector();
String response = connector.connect("link"); // (Returns a String value of the JSON)
final Gson gson = new Gson();
final Summoner summoner = gson.fromJson(response, Summoner.class); //Summoner is a model class
System.out.println(summoner);
Summoner class:
public class Summoner {
private String name;
private long profileIconId;
private long summonerLevel;
private long revisionDate;
public String getName() {
return name;
}
public void setName(final String name) {
this.name = name;
}
public long getProfileIconId() {
return profileIconId;
}
public void setProfileIconId(final long profileIconId) {
this.profileIconId = profileIconId;
}
public long getSummonerLevel() {
return summonerLevel;
}
public void setSummonerLevel(final long summonerLevel) {
this.summonerLevel = summonerLevel;
}
public long getRevisionDate() {
return revisionDate;
}
public void setRevisionDate
(long revisionDate) {
this.revisionDate = revisionDate;
}
#Override
public String toString() {
return "Summoner{" +
"name='" + name + '\'' +
", profileIconId=" + profileIconId +
", summonerLevel=" + summonerLevel +
", revisionDate=" + revisionDate +
'}';
}
}
And I get the following output on the console:
Summoner{name='null', profileIconId=0, summonerLevel=0, revisionDate=0}
I have sadly no idea why this happens. Any help I get is appreciated. I am fairly sure it has to do with the JSON output that "nameOfSummoner" is on top and maybe that's why it does not read what is below.

As mentioned by #PeterMmm , your input is a map with 1 key-value pair.
You need to Create another POJO with Summoner object as attribute:
public class Sample {
private Summoner nameOfSummoner;
//getters and setters
}
and then try parsing. Or, you could create a Map and parse.
Map<String, Summoner> responseObj = new HashMap<String, Summoner>();
responseObj= gson.fromJson(response, responseObj.class);
Summoner obj = responseObj.get("nameOfSummoner");
You will also need to have "id" attribute in Summoner class I believe, else gson will throw an exception.