Retrofit is a type-safe REST client library for Android and Java that allows defining REST APIs as Java interfaces. It simplifies HTTP communication by converting remote APIs into declarative interfaces. It supports synchronous, asynchronous, and observable API consumption. The Retrofit library was created by Square.

1. Retrofit Showcase
A type-safe REST client for Android and Java
THJUG #1 2015
Amin Cheloh

2. Retrofit
● Retrofit turns your REST API into a Java
interface.
● Simplifies HTTP communication by turning
remote APIs into declarative, type-safe
interfaces
● By Square (Jake Wharton)

3. Declaring API
Synchronous
public interface GitHubService {
@GET("/repos/{owner}/{repo}
/contributors")
List<Contributor> contributors(
@Path("owner") String owner,
@Path("repo") String repo
);
}

4. Declaring API (con.)
Asynchronous
@GET("/repos/{owner}/{repo}/contributors")
void contributors(
@Path("owner") String owner,
@Path("repo") String repo,
Callback<List<Contributor>> callback
);

5. Declaring API (con.)
Observable
@GET("/repos/{owner}/{repo}/contributors")
Observable<List<Contributor>> contributors(
@Path("owner") String owner,
@Path("repo") String repo
);

6. Declaring API (con.)
public class Contributor {
public String login; // GitHub username.
public int contributions; // Commit count.
}

7. Declaring API (con.)
some annotations
● @DELETE
● @POST
● @PUT
● @Query
● @Header
● @FormUrlEncoded
● @Multipart
● @Part

8. Using RestAdapter
RestAdapter is the class which transforms an
API interface into an object which actually
makes network requests.

9. Using RestAdapter (con.)
RestAdapter restAdapter = new RestAdapter.Builder()
.setRequestInterceptor(new RequestInterceptor() {
@Override
public void intercept(RequestFacade request) {
request.addQueryParam("version", "2");
}
})
.setConverter(new GsonConverter(gson))
.setEndpoint(ServerApi.getApiServerUri())
.setLogLevel(RestAdapter.LogLevel.BASIC)
.build();

10. Consume API
Synchronous
List<Contributor> contributors = restAdapter.contributors
("square", "okhttp");

11. Consume API (con.)
Asynchronous
Callback<List<Contributor>> callback = new
Callback<List<Contributor>> {
@Override
public void success(List<Contributor> contributors,
Response response) {
// TODO consume data
}
@Override
public void failure(RetrofitError error) {
// TODO handle error
}
}

12. Consume API (con.)
Asynchronous
restAdapter.contributors("square", "okhttp", callback);

13. Consume API (con.)
Observable
Observable<List<Contributor>> ob = restAdapter.
contributors("square", "okhttp");
Subscribtion s = AppObservable.bindActivity(this, ob,
new Action1<List<Contributor>>() {
@Override
public void call(List<Contributor> contributors) {
// TODO
}
);
s.unsubscribe();