"Expected BEGIN_OBJECT but was STRING at line 1 column 1"

I have this method:

public static Object parseStringToObject(String json) {
    String Object = json;
    Gson gson = new Gson();
    Object objects = gson.fromJson(object, Object.class);
    parseConfigFromObjectToString(object);
    return objects;
}

And I want to parse a JSON with:

public static void addObject(String IP, Object addObject) {
    try {
        String json = sendPostRequest("http://" + IP + ":3000/config/add_Object", ConfigJSONParser.parseConfigFromObjectToString(addObject));
        addObject = ConfigJSONParser.parseStringToObject(json);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

But I get an error message:

> com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: > Expected BEGIN_OBJECT but was STRING at line 1 column 1

Even without seeing your JSON string you can tell from the error message that it is not the correct structure to be parsed into an instance of your class.

Gson is expecting your JSON string to begin with an object opening brace. e.g.

{

But the string you have passed to it starts with an open quotes

"

Invalid JSON from the server should always be an expected use case. A million things can go wrong during transmission. Gson is a bit tricky, because its error output will give you one problem, and the actual exception you catch will be of a different type.

With all that in mind, the proper fix on the client side is

try
{
  gson.fromJSON(ad, Ad.class);
  //...
}
catch (IllegalStateException | JsonSyntaxException exception)
{
  //...

If you want to know why the JSON you received from the server is wrong, you can look inside your catch block at the exception. But even if it is your problem, it's not the client's responsibility to fix JSON it is receiving from the internet.

Either way, it is the client's responsibility to decide what to do when it gets bad JSON. Two possibilities are rejecting the JSON and doing nothing, and trying again.

If you are going to try again, I highly recommend setting a flag inside the try / catch block and then responding to that flag outside the try / catch block. Nested try / catch is likely how Gson got us into this mess with our stack trace and exceptions not matching up.

In other words, even though I'll admit it doesn't look very elegant, I would recommend

boolean failed = false;

try
{
  gson.fromJSON(ad, Ad.class);
  //...
}
catch (IllegalStateException | JsonSyntaxException exception)
{
  failed = true;
  //...
}

if (failed)
{
  //...

In Retrofit2, When you want to send your parameters in raw you must use Scalars.

first add this in your gradle:

    compile 'com.squareup.retrofit2:retrofit:2.3.0'
    compile 'com.squareup.retrofit2:converter-gson:2.3.0'
    compile 'com.squareup.retrofit2:converter-scalars:2.3.0'

    public interface ApiInterface {

    String URL_BASE = "http://10.157.102.22/rest/";

    @Headers("Content-Type: application/json")
    @POST("login")
    Call<User> getUser(@Body String body);

}

my SampleActivity :

   public class SampleActivity extends AppCompatActivity implements Callback<User> {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sample);

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(ApiInterface.URL_BASE)
                .addConverterFactory(ScalarsConverterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        ApiInterface apiInterface = retrofit.create(ApiInterface.class);


        // prepare call in Retrofit 2.0
        try {
            JSONObject paramObject = new JSONObject();
            paramObject.put("email", "[email protected]");
            paramObject.put("pass", "4384984938943");

            Call<User> userCall = apiInterface.getUser(paramObject.toString());
            userCall.enqueue(this);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }


    @Override
    public void onResponse(Call<User> call, Response<User> response) {
    }

    @Override
    public void onFailure(Call<User> call, Throwable t) {
    }
}

Reference: [https://stackoverflow.com/questions/21398598/how-to-post-raw-whole-json-in-the-body-of-a-retrofit-request][1]

I had a similar problem recently and found an interesting solution. Basically I needed to deserialize following nested JSON String into my POJO:

"{\"restaurant\":{\"id\":\"abc-012\",\"name\":\"good restaurant\",\"foodType\":\"American\",\"phoneNumber\":\"123-456-7890\",\"currency\":\"USD\",\"website\":\"website.com\",\"location\":{\"address\":{\"street\":\" Good Street\",\"city\":\"Good City\",\"state\":\"CA\",\"country\":\"USA\",\"postalCode\":\"12345\"},\"coordinates\":{\"latitude\":\"00.7904692\",\"longitude\":\"-000.4047208\"}},\"restaurantUser\":{\"firstName\":\"test\",\"lastName\":\"test\",\"email\":\"[email protected]\",\"title\":\"server\",\"phone\":\"0000000000\"}}}"

I ended up using regex to remove the open quotes from beginning and the end of JSON and then used apache.commons unescapeJava() method to unescape it. Basically passed the unclean JSON into following method to get back a cleansed one:

private String removeQuotesAndUnescape(String uncleanJson) {
    String noQuotes = uncleanJson.replaceAll("^\"|\"$", "");

    return StringEscapeUtils.unescapeJava(noQuotes);
}

then used Google GSON to parse it into my own Object:

MyObject myObject = new.Gson().fromJson(this.removeQuotesAndUnescape(uncleanJson));

I have come to share an solution. The error happened to me after forcing the notbook to hang up. possible solution clean preject.

Maybe your JSON Object is right,but the response that you received is not your valid data.Just like when you connect the invalid WiFi,you may received a strange response < html>.....< /html> that GSON can not parse.

you may need to do some try..catch.. for this strange response to avoid crash.

Make sure you have DESERIALIZED objects like DATE/DATETIME etc. If you are directly sending JSON without deserializing it then it can cause this problem.

In my situation, I have a "model", consist of several String parameters, with the exception of one: it is byte array byte[]. Some code snippet:

String response = args[0].toString();
Gson gson = new Gson();
BaseModel responseModel = gson.fromJson(response, BaseModel.class);

The last line above is when the

java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column

is triggered. Searching through the SO, I realised I need to have some form of Adapter to convert my BaseModel to and fro a JsonObject. Having mixed of String and byte[] in a model does complicate thing. Apparently, Gson don't really like the situation.

I end up making an Adapter to ensure byte[] is converted to Base64 format. Here is my Adapter class:

public class ByteArrayToBase64Adapter implements JsonSerializer<byte[]>, JsonDeserializer<byte[]> {

    @Override
    public byte[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        return Base64.decode(json.getAsString(), Base64.NO_WRAP);
    }

    @Override
    public JsonElement serialize(byte[] src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(Base64.encodeToString(src, Base64.NO_WRAP));
    }
}

To convert JSONObject to model, I used the following:

Gson customGson = new GsonBuilder().registerTypeHierarchyAdapter(byte[].class, new ByteArrayToBase64Adapter()).create();
BaseModel responseModel = customGson.fromJson(response, BaseModel.class);

Similarly, to convert the model to JSONObject, I used the following:

Gson customGson = new GsonBuilder().registerTypeHierarchyAdapter(byte[].class, new ByteArrayToBase64Adapter()).create();
String responseJSon = customGson.toJson(response);

What the code is doing is basically to push the intended class/object (in this case, byte[] class) through the Adapter whenever it is encountered during the convertion to/fro JSONObject.

Don't use jsonObject.toString on a JSON object.

In my case, I am Returning JSON Object as

> {"data":"","message":"Attendance Saved > Successfully..!!!","status":"success"}

Resolved by changing it as

> {"data":{},"message":"Attendance Saved > Successfully..!!!","status":"success"}

Here data is a sub JsonObject and it should starts from { not ""

if your json format and variables are okay then check your database queries...even if data is saved in db correctly the actual problem might be in there...recheck your queries and try again.. Hope it helps

Don't forget to convert your object into Json first using Gson()

  val fromUserJson = Gson().toJson(notificationRequest.fromUser)

Then you can easily convert it back into an object using this awesome library

      val fromUser = Gson().fromJson(fromUserJson, User::class.java)

I had a case where I read from a handwritten json file. The json is perfect. However, this error occurred. So I write from a java object to json file, then read from that json file. things are fine. I could not see any difference between the handwritten json and the one from java object. Tried beyondCompare it sees no difference. I finally noticed the two file sizes are slightly different, and I used winHex tool and detected extra stuff. So the solution for my situation is, make copy of the good json file, paste content into it and use.

In my case, my custom http-client didn't support the gzip encoding. I was sending the "Accept-Encoding: gzip" header, and so the response was sent back as a gzip string and couldn't be decoded.

The solution was to not send that header.

I was making a POST request with some parameters using Retrofit in Android

WHAT I FACED:

The error I was getting in Android Studio logcat:

> java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING > at line 2 column 1 path $

[but it was working fine with VOLLY library]

when I googled it... you know[ Obviously json is expecting a OBJECT but...]

BUT when I changed my service to return a simple string [ like print_r("don't lose hope") ] or Noting at all

It was getting printed fine in Postman but in Android studio logcat, it was still SAME ERROR [

> java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING > at line 2 column 1 path $

]

Hold up now, I am sending a simple message or not sending anything in response and still studio is telling me "...Expected BEGIN_OBJECT but was STRING..." SOMETHING IS WRONG

On 4th day: I finally stopped for looking "QUICK SOLUTIONS" and REALLY READ some stack overflow questions and articles carefully.

WHAT I GOT:

Logging interceptor

It will show you whatever data comes from your server[even eco messages] which are not shown in Andorid studios logcat, that way you can FIND THE PROBLEM.

What I found is I was sending data with @Body like-

@Headers("Content-Type: application/json")
@POST("CreateNewPost")
Call<Resp> createNewPost(@Body ParaModel paraModel);

but no parameter was reaching to server, everything was null [I found using Logging interceptor]

then I simply searched an article "how to make POST request using Retrofit" here's one

SOLUTION:

from here I changed my method to:

@POST("CreateNewPost")
@FormUrlEncoded
Call<Resp> createNewPost(
    @Field("user_id") Integer user_id,
    @Field("user_name") String user_name, 
    @Field("description") String description,
    @Field("tags") String tags);

and everything was fine.

CONCLUSION:

I don't understand why Retrofit gave this error

> java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING > at line 2 column 1 path $

it doesn't make any sense at all.

So ALWAYS DEBUG in detail then find WHERE THINGS ARE LEAKING and then FIX.

This error solved for by replacing .toString method to .string on the response

toString => string (add in try{...code..}catche(IOException e))

below code is working for me 

try {
     MainModelResponse model;
     Gson gson = new GsonBuilder().create();
     if (response.code() == ConstantValues.SUCCESS_OK) {
         model = gson.fromJson(response.body().string(), MainModelResponse.class);
     } else {
       model = gson.fromJson(response.errorBody().string(), MainModelResponse.class);
                    }
                    moduleData.postValue(model);
                }catch (IllegalStateException | JsonSyntaxException | IOException exception){
                    exception.printStackTrace();
                }

}

use a string begin & end with {}.

such as

final String jsStr = "{\"metric\":\"opentsdb_metric\",\"tags\":{\"testtag\":\"sunbotest\"},\"aggregateTags\":[],\"dps\":{\"1483399261\":18}}";

DataPoint dataPoint = new Gson().fromJson(jsStr, DataPoint.class);

this works for me.

In my case the object was all fine even the Json Validator was giving it a valid resposne but I was using Interface like this

@POST(NetworkConstants.REGISTER_USER)
Call<UserResponse> registerUser(
        @Query("name") String name,
        @Query("email") String email,
        @Query("password") String password,
        @Query("created_date") Long creationDate
);

Then I changed the code to

@FormUrlEncoded
@POST(NetworkConstants.REGISTER_USER)
Call<UserResponse> registerUser(
        @Field("name") String name,
        @Field("email") String email,
        @Field("password") String password,
        @Field("created_date") Long creationDate
);

And everything was resolved.

my problem not related to my codes

after copy some files from an other project got this issue

in the stack pointed to Gson library

in android studio 4.2.1 this problem not solved when I try file-> invalidate and restart

and

after restart in first time build got same error but in second build this problem solved

I don't understand why this happened

I was using an old version of retrofit library. So what I had to do was to change my code from this after upgrading it to com.squareup.retrofit2:retrofit:2.9.0:

@POST(AppConstants.UPLOAD_TRANSACTION_DETAIL)
fun postPremiumAppTransactionDetail(
   @Query("name") planName:String,
   @Query("amount") amount:String,
   @Query("user_id") userId: String,
   @Query("sub_id") planId: String,
   @Query("folder") description:String,
   @Query("payment_type") paymentType:String):
Call<TransactionResponseModel>

To this:

@FormUrlEncoded
@POST(AppConstants.UPLOAD_TRANSACTION_DETAIL)
fun postPremiumAppTransactionDetail(
   @Field("name") planName:String,
   @Field("amount") amount:String,
   @Field("user_id") userId: String,
   @Field("sub_id") planId: String,
   @Field("folder") description:String,
   @Field("payment_type") paymentType:String):
Call<TransactionResponseModel>