@SerializedName bug in Java when it's used with Retrofit2 library

Gson version

2.9.0

Java / Android version

java 17

Used tools

-Maven wrapper 3.8.4

Description

@SerializedName is not properly serialized in object.The deserialization from URL json to object is ok but not the serialization. If i use @JsonProperty the name is correctly serialized.

Expected behavior

I expect the SerializedName should be used which is “bookNameTest” when I get the return Object but it’s not, it’s only printed out correctly in the std but if you get the object as return, the response is not correct @SerializedName(“bookNameTest”) private String bookName;

Actual behavior

{ retrofit2.Response<Book> response = bookClient.getBook(“api/v1/bookService/otherBooks”).execute(); return response.body(); }

=> Wrong behavior here, i expect “bookNameTest”: “JWT” but it’s printed “bookName”=“JWT”

{
    "bookId": 1,
    "price": 22.25,
    "bookName": "JWT"
}

Reproduction steps

1. Create class Book.java

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Book {
    private int bookId;
    private double price;

    @SerializedName("bookNameTest")
    private String bookName;
}

1. Create a GET API

@GetMapping(value = "/bookService/otherBooks", produces = MediaType.APPLICATION_JSON_VALUE)
      public Book getOtherBook(@RequestParam(required = false) String bookID) throws IOException {
      retrofit2.Response<Book> response = bookClient.getBook("api/v1/bookService/otherBooks").execute();
      Gson gson = new GsonBuilder().setPrettyPrinting().create();
      String jsonString = gson.toJson(response.body());
      System.out.println(jsonString);
      System.out.println(response.body());
      return response.body();
}

The mock Json response from URL endpoint “api/v1/bookService/otherBooks”

{
    "bookId": 1,
    "price": 22.25,
    "bookNameTest": "JWT"
}

Please note for bookClient I used Retrofit and use Gson converter. And then the deserialization is correctly done but after that the serialization to use the @SerializedName is not correct.

public bookClient bookClient(){
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
                .build();

        return new Retrofit.Builder()
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl("/") //can use localhost
                .client(okHttpClient)
                .build().create(bookClient.class);

I have checked the jsonString is printed out correctly from console using System.out.println(jsonString)

{
  "bookId": 1,
  "price": 22.25,
  "bookNameTest": "JWT"
}

but the return response.body() is not Book(bookId=1, price=22.25, bookName=JWT}

==================================================== If inside Book.java, i used @JsonProperty, the book can be deserialized and serialized correctly. With using the same code, the return object, it will use @JsonProperty name which is “bookNameTest”

import com.fasterxml.jackson.annotation.JsonProperty;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Book {
    private int bookId;
    private double price;

    @JsonProperty("bookNameTest")
    private String bookName;
    private Author author;
    private Date publishedDate;
}

Correct output

{
    "bookId": 1,
    "price": 22.25,
    "bookNameTest": "JWT"
}

Exception stack trace

[harrylhp]

Hi Marco, i have found the issue, it’s from SpringBoot configuration. I need to add a new config inside application.yml to force it to use Gson

spring
  mvc:
    converters:
      preferred-json-mapper: gson

Thank for your time. I think i’ll close the issue as it’s not a bug it’s SpringBoot configuration 😃

[harrylhp]

Hi Marco For me to force using Gson, i have defined the converter inside the Client before sending http Request and it’s using Gson. Else if i define to use .addConverterFactory(JacksonConverterFactory.create()), the Gson initialization will fail so i’m pretty sure my SpringBoot is using Gson at the time of converting.

public bookClient bookClient(){
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
                .build();

        return new Retrofit.Builder()
                .**addConverterFactory(GsonConverterFactory.create())**
                .baseUrl("/") //can use localhost
                .client(okHttpClient)
                .build().create(bookClient.class);

For Lombok, i have checked the generated classes toString for both @SerializedName and @JsonProperty i don’t see any dfiference. So it’s kind of confusing me for the Gson behavior, as you could see the Serialized String from println is correct, but if calling the response.body() to get Object, it’s not as I expected the library will behave