Logging with Retrofit 2

I’m trying to get the exact JSON that is being sent in the request. Here is my code:

OkHttpClient client = new OkHttpClient();
client.interceptors().add(new Interceptor(){
   @Override public com.squareup.okhttp.Response intercept(Chain chain) throws IOException {
      Request request = chain.request();
      Log.e(String.format("nrequest:n%snheaders:n%s",
                          request.body().toString(), request.headers()));
      com.squareup.okhttp.Response response = chain.proceed(request);
      return response;
   }
});
Retrofit retrofit = new Retrofit.Builder()
   .baseUrl(API_URL)
   .addConverterFactory(GsonConverterFactory.create())
   .client(client).build();

But I only see this in the logs:

request:
com.squareup.okhttp.RequestBody$1@3ff4074d
headers:
Content-Type: application/vnd.ll.event.list+json

How am I supposed to do proper logging, given the removal of setLog() and setLogLevel() which we used to use with Retrofit 1?

Answer

In Retrofit 2 you should use HttpLoggingInterceptor.

Add dependency to build.gradle. Latest version as of October 2019 is:

implementation 'com.squareup.okhttp3:logging-interceptor:4.2.1'

Create a Retrofit object like the following:

HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
OkHttpClient client = new OkHttpClient.Builder().addInterceptor(interceptor).build();

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://backend.example.com")
        .client(client)
        .addConverterFactory(GsonConverterFactory.create())
        .build();

return retrofit.create(ApiClient.class);

In case of deprecation warnings, simply change setLevel to:

interceptor.level(HttpLoggingInterceptor.Level.BODY);

The above solution gives you logcat messages very similar to the old ones set by

setLogLevel(RestAdapter.LogLevel.FULL)

In case of java.lang.ClassNotFoundException:

Older Retrofit version might require an older logging-interceptor version. Take a look at comments sections for details.