Retrofit is a library that transforms HTTP APIs into Java interfaces. It simplifies HTTP calls by allowing developers to define API endpoints as method calls and handles serialization of responses to POJOs. Retrofit abstracts away the complexities of making HTTP requests and responses, making network calls simpler and easier to manage. It supports synchronous and asynchronous calls, handles errors gracefully, and allows pluggable HTTP clients and converters. Overall, Retrofit cleans up network code and makes communicating with APIs more straightforward.

1. Simplificando chamadas
HTTP com o Retrofit
Felipe Pedroso
felipepedroso
felipeapedroso

2. Cenário – Rest APIs
API

3. HTTP Request
• Código extenso
• Tratamento de erros?
• Aonde estão os filmes?
(domínio do problema)
• JSON de Resposta em
um String (falta o parse)
HttpURLConnection urlConnection = null;
URL url = null;
try {
url = new
URL("http://api.themoviedb.org/3/movie/upcoming?api_key=<KEY>");
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
BufferedReader reader = new BufferedReader(new
InputStreamReader(inputStream));
StringBuffer buffer = new StringBuffer();
String line;
while ((line = reader.readLine()) != null) {
buffer.append(line + "n");
}
String jsonAnswer = buffer.toString();
} catch (IOException e) {
e.printStackTrace();
} finally {
urlConnection.disconnect();
}

4. Resposta

5. Resposta (+ bonita)

7. Retrofit
• Biblioteca que transforma a
API HTTP em uma interface
Java
• Criada pela Square Inc.
• Disponível no Github
• Funciona no Android e Java
SE (Gradle, Maven e JAR)

8. Mas o que ele oferece?

9. Interface Service
• Suporta @GET, @POST e @PUT
• Vários tipos de parâmetros: @Query, @Path, @Header, etc
public interface MoviesService {
@GET("movie/upcoming")
Call<MovieResults> listUpcomingMovies();
@GET("movie/{movieId}/similar")
Call<MovieResults> listSimilarMovies(@Path("movieId") Integer movieId);
}

10. Objeto ‘Service’
Retrofit retrofit = new Retrofit.Builder()
.baseUrl("http://api.themoviedb.org/3/")
.addConverterFactory(GsonConverterFactory.create())
.build();
MoviesService moviesService =
retrofit.create(MoviesService.class);

11. {
"poster_path":"/lFSSLTlFozwpaGlO31OoUeirBgQ.jpg",
"adult":false,
"overview":"Jason Bourne, now remembering who he tru
ly is, tries to uncover hidden truths about his past.",
"release_date":"2016-07-28",
"genre_ids":[
28
],
"id":324668,
"original_title":"Jason Bourne",
"original_language":"en",
"title":"Jason Bourne",
"backdrop_path":"/AoT2YrJUJlg5vKE3iMOLvHlTd3m.jp
g",
"popularity":6.463538,
"vote_count":52,
"video":false,
"vote_average":3.97
}
Resposta  POJO*
public class MovieInfo {
private Integer id;
private String poster_path;
private String title;
public Double vote_average;
public String release_date;
public String overview;
....
}
* POJO: “Plain Old Java Object”

12. Chamada Síncrona
Response<MovieResults> response = null;
try {
response = moviesService.listUpcomingMovies().execute();
MovieResults movieResults = response.body();
} catch (IOException e) {
e.printStackTrace();
}

13. Chamada Assíncrona
moviesService.listUpcomingMovies().enqueue(new Callback<MovieResults>() {
@Override
public void onResponse(Call<MovieResults> call, Response<MovieResults> response) {
MovieResults movieResults = response.body();
}
@Override
public void onFailure(Call<MovieResults> call, Throwable t) {
// Handle failure
}
});

14. Outras características
• Código mais simples
• Tratamento de erros mais fácil
• Cliente HTTP plugável (Ex.: OkHttp, ApacheHttp, etc)
• Converters (Serialização) plugáveis (Ex.: Gson, XML, etc)
• Compatível com RxJava (programação reativa)

15. Exemplo
• JavaFX
github.com/felipepedroso/Upco
mingMoviesFX
• Console
github.com/felipepedroso/Upco
mingMoviesConsole
• Disponível em:
github.com/felipepedroso/Retro
fitMoviesExample

16. Referências
• Retrofit – Site Oficial
• Retrofit – Github
• Realm 2 – Jake Wharton
• Android Libs – Retrofit – Daniel Gimenes
• Ícones: https://www.iconfinder.com/AlfredoCreates

17. Dúvidas?

18. Obrigado!
felipepedroso
felipeapedroso