Prior to Froyo, HttpURLConnection had some frustrating bugs. In particular, calling close() on a readable InputStream could poison the connection pool...

...the large size of this API makes it difficult for us to improve it without breaking compatibility. The Android team is not actively working on Apache HTTP Client.

From Android's HTTP Clients - Android Developers Blog

public static JSONObject requestRestResponse() {
    HttpURLConnection urlConnection = null;
    try {
        // create connection
        URL urlToRequest = new URL("http://mybackend.com/v1/req");
        urlConnection = (HttpURLConnection)
            urlToRequest.openConnection();
        urlConnection.setConnectTimeout(CONNECTION_TIMEOUT);
        urlConnection.setReadTimeout(DATARETRIEVAL_TIMEOUT);
                

        // handle issues
        int statusCode = urlConnection.getResponseCode();
        if (statusCode == HttpURLConnection.HTTP_UNAUTHORIZED) {
            // handle unauthorized (if service requires user login)
        } else if (statusCode != HttpURLConnection.HTTP_OK) {
            // handle any other errors, like 404, 500,..
        }

        // create JSON object from content
        InputStream in =
            new BufferedInputStream(urlConnection.getInputStream());
        return new JSONObject(getResponseText(in));
                

    } catch (MalformedURLException e) {
        // URL is invalid
    } catch (SocketTimeoutException e) {
        // data retrieval or connection timed out
    } catch (IOException e) {
        // could not read response body
    } catch (JSONException e) {
        // response body is no valid JSON string
    }
    return null;
}} finally {
        if (urlConnection != null) {
            // Don't forget to release resources
            urlConnection.disconnect();
        }
    }
    return null;
}

Don't forget about NetworkOnMainThreadException. The most common solution for this kind of problems are AsyncTasks!

Have you ever wrote?

@Override
protected void onPostExecute(String result) {
  if (getActivity() == null){
    return; // Here Activity is gone...
  }
  ...
}
            
            

• Request cancellation
• Parallel request
• Scheduling
• Caching
• ...and boilerplate?

If you have more than

1K lines

of code for creating and handling your HTTP requests...

Ask yourself if you're doing it right!

• Retrofit
• Volley
• OkHTTP
• Picasso
• ...and more

• From square.github.io
• Works with Java Annotations
• Support both Sync/Async execution
• Apache 2 Licensed
• Recently released (2016-03-11 v2.0.0)

compile 'com.squareup.retrofit2:retrofit:2.0.0'
                

public interface GitHubService {
  @GET("users/{user}/repos")
  Call<List<Repo>> listRepos(@Path("user") String user);
}
            

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.github.com/")
    .build();

GitHubService service = retrofit.create(GitHubService.class);
                

public interface GitHubService {
  @GET("users/{user}/repos")
  Call<List<Repo>> listRepos(
            @Path("user") String user);

  @GET("users/{user}/repos")
  Call<List<Repo>> listRepos(
            @Path("user") String user,
            @Query("type") String type);

  @GET("users/{user}/repos")
  Call<List<Repo>> listRepos(
            @Path("user") String user,
            @QueryMap Map<String, String> options);
}
                

public interface GitHubService {
    @Headers("User-Agent: my-Awesome-Retrofit-powered-app")
    @GET("users/{user}/repos")
    Call<List<Repo>> listRepos(@Path("user") String user);

    @GET("gists/public")
    Call<List<Gist>> listGists(@Header("User-Agent") String uAgent)
}
                

public interface GitHubService {
    @GET
    Call<List<User>> getCustomUsers(@Url String reqUrl);

    @POST("gists")
    Call<Gist> createGist(@Body GistRequest grequest);
}
                

• Gson com.squareup.retrofit:converter-gson
• Jackson com.squareup.retrofit:converter-jackson
• Moshi com.squareup.retrofit:converter-moshi
• Protobuf com.squareup.retrofit:converter-protobuf
• Wire com.squareup.retrofit:converter-wire
• Simple XML com.squareup.retrofit:converter-simplexml

You can also implement yours with Converter.Factory

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://api.github.com/")
        .addConverterFactory(JacksonConverterFactory.create())
        .build();

service = retrofit.create(GitHubService.class);
                

Gson gson = new GsonBuilder()
        .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
        .create();

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://api.github.com/")
        .addConverterFactory(GsonConverterFactory.create(gson))
        .build();

service = retrofit.create(GitHubService.class);
                

You can plug a Call Adapter to work with:

• Observables (RxJava)
• ListeanableFuture (Guava)
• CompletableFuture (Java8)

// Sync call

Call<Repo> call = service.loadRepo();
Response<Repo> response = call.execute();
                

// Async call

Call<Repo> call = service.loadRepo();
call.enqueue(new Callback<Repo>() {
    @Override
    public void onResponse(Response<Repo> response) {
        // Get result Repo from response.body()
    }
    
    @Override
    public void onFailure(Throwable t) {
        // Handle failure
    }
});
                

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.github.com/")
    .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
    .build();
                

public interface APIService {
    
    @GET("gists/public")
    Call<Gists> getGists();

    @GET("gists/public")
    Observable<Gists> getGistsRx();
}
                

getGistsRx().subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(gists -> {
        Toast.makeText(getApplicationContext(),
            "Fetched gists: " + gists.size(),
             Toast.LENGTH_SHORT).show();
        });
                

Interface Declaration

public interface GitHubService {
    @POST("/list")
    Repo loadRepo();

    @POST("/list")
    void loadRepo(Callback<Repo> cb);
}
            

public interface GitHubService {
    @POST("/list")
    Call<Repo> loadRepo();
}
            

OkHttp Interceptors

HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();

// Choose desired logging level
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY); // Or FULL

OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(interceptor).build();

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://api.github.com/")
        .client(client)
        .build();
            

compile 'com.squareup.okhttp3:logging-interceptor:3.2.0'

Certificate Pinning

OkHttpClient client = new OkHttpClient.Builder()
    .certificatePinner(new CertificatePinner.Builder()
    .add("example.com", "sha1/DmxUShsZuNiqPQsX2Oi9uv2sCnw=")
    .add("example.com", "sha1/SXxoaOSEzPC6BgGmxAt/EAcsajw=")
    .build())
.build();
                

Use CertificatePinner to restrict which certificates and certificate authorities are trusted.

Certificate pinning increases security, but limits your server team’s abilities to update their TLS certificates.

Do not use certificate pinning without the blessing of your server’s TLS administrator!

From OkHTTP Official Wiki

...and more!

• OkHTTP as default RAW HTTP Client
• GSON Converter not by default
• New URL resolving mechanism
• setEndpoit baseURL
• RestAdapter Retrofit
• Dynamic URLs
• Request cancellation

call.cancel();

• From Google
• Available from the AOSP repo
• Excellent for populating the UI with text and images
• Excellent for caching
• Apache 2 licensed
• Not well documented :(

compile 'com.android.volley:volley:1.0.0'
                

Thread model

RequestQueue queue =
    Volley.newRequestQueue(getApplicationContext());

StringRequest request = new StringRequest(
    Request.Method.GET,
    "https://api.github.com/gists/public",
    this::handleResponse,
    this::handleError);

request.setShouldCache(true);
request.setTag(requestTag); // A class member 'requestTag'

queue.add(request);
                

@Override
protected void onStop() {
    queue.cancelAll(requestTag);
    super.onStop();
}
                

Don't forget to do it!

ImageLoader mImageLoader;
NetworkImageView mNetworkImageView;

private static final String IMAGE_URL =
    "http://i.imgur.com/RLKixQW.png";

// Retrieve the ImageLoader (singleton/application/...)
// Retrieve the NetworkImageView (findViewById)

mNetworkImageView.setImageUrl(IMAGE_URL, mImageLoader);
                

<com.android.volley.toolbox.NetworkImageView
        android:id="@+id/networkImageView"
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_centerHorizontal="true" />
                

mImageLoader = new ImageLoader(mRequestQueue,
        new ImageLoader.ImageCache() {

    private final LruCache<String, Bitmap> cache = new LruCache<>(20);

    @Override
    public Bitmap getBitmap(String url) {
        return cache.get(url);
    }

    @Override
    public void putBitmap(String url, Bitmap bitmap) {
        cache.put(url, bitmap);
    }
});
                

~$ adb shell setprop log.tag.Volley VERBOSE
                

D/Volley (670  ms) [ ] https://api.github.com/users/cortinico
D/Volley (+0   ) [ 1] add-to-queue
D/Volley (+0   ) [238] cache-queue-take
D/Volley (+0   ) [238] cache-miss
D/Volley (+10  ) [242] network-queue-take
D/Volley (+630 ) [242] network-http-complete
D/Volley (+0   ) [242] network-parse-complete
D/Volley (+0   ) [242] network-cache-written
D/Volley (+0   ) [242] post-response
D/Volley (+30  ) [ 1] done
D/Volley (10   ms) [ ] https://api.github.com/users/cortinico
D/Volley (+0   ) [ 1] add-to-queue
D/Volley (+0   ) [238] cache-queue-take
D/Volley (+0   ) [238] cache-hit
D/Volley (+0   ) [238] cache-hit-parsed
D/Volley (+0   ) [238] post-response
D/Volley (+10  ) [ 1] done
                

• Want less and elegant code? ...Retrofit!
• Want control over scheduling/caching? ...Volley!
• Want image management? Volley! ...or Retrofit + Picasso
• Default choose? ...Retrofit!