Presentation from the Charlotte Android developers meetup on 3/10/2015 at Skookum Digital Works. One of the most common things done when writing mobile applications is accessing RESTful web-services. This normally requires a lot of boilerplate code, but it doesn’t have to. Retrofit from Square is an Android networking library that takes a lot of pain out of networking code. During the talk we’ll examine Retrofit in-depth and discuss its benefits. We’ll also discuss areas it could improve

1. Android + Retrofit +
REST + JSON = Easy
presented by Chris Ollenburg

2. Basic REST API
• Create - http://www.fakeservice.com/user
• Read - http://www.fakeservice.com/user/{id}
• Update - http://www.fakeservice.com/user/{id}?
name={new name}
• Delete - http://www.fakeservice.com/user/{id}

3. public interface UserService {
@POST("/user") // CREATE
void createUser(@Body User user);
@GET("/user/{userId}") // READ
User getUser(@Path("userId") String userId);
@PUT("/user/{userId}") // UPDATE
void updateUserName(@Path("userId") String userId,
@Body User user);
@DELETE(“/user/{userId}“) // DELETE
void deleteUser(@Path("userId") String userId);
}
public class User {
String name;
Date birthDate;
Integer age;
}

4. Synchronous
public interface MyService {
@GET(“/test")
Message getMessage();
}

5. Asynchronous
public interface MyService {
@GET(“/test")
void getMessage(Callback<Message> msg);
}

6. Observable / Rx
public interface MyService {
@GET(“/test")
Observable<Message> getMessage();
}

7. Path Variables
@GET("/user/{userId}") // READ
User getUser(@Path("userId") String userId);

8. Query Parameters
@GET("/user") // READ
User getUser(@Query("userId") String userId);

9. Http Headers
@Headers({"Accept: application/json”})
@GET(“/user/self“)
User getUser(@Header("Authorization") String auth)

10. Request Body
@PUT("/user/{userId}")
void updateUserName(@Path("userId") String userId,
@Body User user);
@Multipart
@POST(“/user")
void createUser(@Part("fName") String fName,
@Part("lName") String lName);
@FormUrlEncoded
@POST(“/user")
void createUser(@Field("fName") String fName,
@Field("lName") String lName);

11. Sync Call
public void sendSync() {
RestAdapter restAdapter = new RestAdapter.Builder()
.setEndpoint(“http://www.myservice.com")
.build();
DemoService service = restAdapter.create(DemoService.class);
DemoModel rep = service.getMessage(apiId);
// Do something w/ object
}

12. Async Call
public void sendAsyncButton() {
service.getMessage(apiId, new Callback<DemoModel>() {
@Override
public void success(DemoModel demoModel, retrofit.client.Response response) {
MainActivity.this.contentView.setText(demoModel.message);
}
@Override
public void failure(RetrofitError error) {
Log.e(TAG, error.getMessage());
MainActivity.this.contentView.setText(error.getMessage());
}
});
}

13. Call w/ RxJava
public void sendRx() {
Observable<DemoModel> observable = service.getMessageRx(apiId);
observable.subscribe(new Action1<DemoModel>() {
@Override
public void call(DemoModel demoModel) {
MainActivity.this.contentView.setText(demoModel.message);
}
});
}

14. Extras
• Adjustable logging level
• Custom GSON deserializers
• Custom deserializer
• Custom Http Client Implementations

15. Gotcha
Not Cancelable

16. Demo

17. Chris Ollenburg
• Principal Consultant at Cardinal Solutions
collenburg@cardinalsolutions.com
@cardinalNow
www.cardinalsolutions.com
• CTO of Taggd’ LLC
chris@taggdstreetart.com
www.taggdstreetart.com
Links
http://square.github.io/retrofit/
https://github.com/OllenDev/RetrofitDemo