Retrofit2 java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $

Question

I've to create/register new User using retrofit2 my server side is

<?php

    $name= $_POST['name'];
    $email = $_POST['email'];
    $password= $_POST['password'];
    $gender= $_POST['gender'];

    $con = mysqli_connect("localhost", "root", "qwerty", "db");
    $query= mysqli_query($con, "INSERT INTO users(name,email, password, gender) VALUES('$name','$email', '$password', '$gender')");

    if($query){
        echo "You are sucessfully Registered";
    }

    else{
        echo "your details could not be registered";
    }

    mysqli_close($con);

?>

my model class is

public class User {

    @SerializedName("name")
    @Expose
    public String name;
    @SerializedName("email")
    @Expose
    public String email;
    @SerializedName("password")
    @Expose
    public String password;
    @SerializedName("gender")
    @Expose
    public String gender;

    public User(String name, String email, String password, String gender) {
        this.name = name;
        this.email = email;
        this.password = password;
        this.gender = gender;
    }

POST in service is

@POST("register.php")
Call<User> createUser(@Body User user);

posting data as

mRegisterButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (validateForm()){
                    mUserCall = mRestManager.getJobService()
                            .createUser(new User(mNameEditText.getText().toString(),
                                                mEmailEditText.getText().toString(),
                                                mPasswordEditText.getText().toString(),
                                                mGenders[position]));
                    mUserCall.enqueue(new Callback<User>() {
                        @Override
                        public void onResponse(Call<User> call, Response<User> response) {
                            User user1 = response.body();
                            Toast.makeText(getApplicationContext(), user1.name , Toast.LENGTH_SHORT).show();
                        }

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

                            Log.e("REGISTER_ERROR", "Message is " + t.getMessage() );
                        }
                    });
                }
            }
        });

I'm getting error

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

I've found some solutions and made change accordingly as

@FormUrlEncoded
    @POST("register.php")
    Call<User> createUser(@Field("name") String name,
                          @Field("email") String email,
                          @Field("password") String password,
                          @Field("gender") String gender);

but it also does not work, same error message, how to solve this error.

Answer 1

Check your response, it is different than you are expecting.

Json must have start from "{" also response is different than your Pojo User so make new Pojo from new response.

Answer 2

I was also getting Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $ error even though I knew server was returning valid json.

After some hours debugging this I discovered it was due to me setting Accept-Encoding: gzip header to the request. This actually tells okhttp not to unzip the response and that the caller will do it himself. Due to this gson was trying to deserialize unzipped response and it's no wonder this was failing.