Retrofit 2.0 Cant convert Request Body to JSON - post

Question

I hope someone can help me.
I try to send a POST Request with a JSON Body using Retrofit 2.0.
Interface:
public interface Interface {
#POST(/*path*/)
Call<MyResponseObject> sendInt(#Body MyInteger myInt);
}
MyInteger class:
public class MyInteger {
int id;
public MyInteger(int id) {
this.id = id;
}
}
Part of MainActivity:
private Retrofit mRetrofit = null;
private final Interface mService;
...
...
mRetrofit = new Retrofit.Builder()
.baseUrl(/*URL*/)
.addConverterFactory(GsonConverterFactory.create())
.build();
mService = mRetrofit.create(Interface.class);
The call:
MyInteger id = new MyInteger(0);
mService.sendInt(id).enqueue(new Callback<MyResponseObject>() {
#Override
public void onResponse(Call<MyResponseObject> call, Response<MyResponseObject> response) {/*Log something*/}
#Override
public void onFailure(Call<MyResponseObject> call, Throwable t) {}
});
In my Opinion it's like this example:
https://futurestud.io/blog/retrofit-send-objects-in-request-body
But the GsonConverter cant convert MyInteger to JSON..
Here is the Log:
java.lang.IllegalArgumentException: Unable to create #Body converter for class com.??.MyInteger (parameter #1)
for method Interface.sendInt
...
...
Caused by: java.lang.IllegalArgumentException: Could not locate RequestBody converter for class com.??.MyInteger.
Tried:
* retrofit2.BuiltInConverters
* retrofit2.GsonConverterFactory
at retrofit2.Retrofit.nextRequestBodyConverter(Retrofit.java:288)
at retrofit2.Retrofit.requestBodyConverter(Retrofit.java:248)
at retrofit2.RequestFactoryParser.parseParameters(RequestFactoryParser.java:491)

Answer 1

I had the same problem. The root cause was that I was using incompatible libraries.
This combination works for me:
<dependency>
<groupId>com.squareup.retrofit2</groupId>
<artifactId>retrofit</artifactId>
<version>2.0.0-beta4</version>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.6.2</version>
</dependency>
<dependency>
<groupId>com.squareup.retrofit2</groupId>
<artifactId>converter-gson</artifactId>
<version>2.0.0-beta4</version>
</dependency>