Android Academy Advanced 2

1. Artyom Okun
31/7/18
Advanced sessions
Networking
2

2. Networking is Huge Topic
Let’s Talk Dugri

3. Networking is Huge Topic
Retrofit
RESTHTTP
Web ServicesOkHttp

4. Nice to Meet You
● Name - Artyom
● Age - 32
● At Android Academy for 4 years
● 2 of them as Mentor
● Work @Colu as Mobile Developer(yes iOS too)

5. Meet Colu App

6. Retrofit

7. What is Retrofit?
•Retrofit is a type-safe HTTP client for Android
•Uses an abstraction, by defining interfaces representing APIs
•Can be ”upgraded” with different type adapter, JSON parsers, interceptors, call
adapters
•Uses by default OkHttp as HTTP engine

8. Retrofit Refresher - Steps to Initialisation
1. Add Retrofit dependency in build.gradle
2. Add permission in AndroidManifest.xml
3. Create an Interface abstraction representing server APIs
4. Create ServiceProvider.java
1. Declare BaseURL for all requests
2. Create and configure OkHttp client
3. Create Retrofit Instance and add OkHttp and BaseUrl to it
4. Expose retrofit.create() method

9. Retrofit Refresher
dependencies {
compile ‘com.squareup.retrofit2:retrofit:2.4.0’
}
build.gradle
AndroidManifest.xml
<uses-permission android:name="android.permission.INTERNET" />

10. Retrofit Refresher
public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}

11. Retrofit Refresher
public class ServiceProvider {
//...
}

12. Retrofit Refresher
// Base URL for all requests
private static final String BASE_URL = “https://coluserver.com/“;
ServiceProvider.java

13. Retrofit Refresher
ServiceProvider.java
private static OkHttpClient httpClient = new OkHttpClient.Builder()
...
.build();

14. Retrofit Refresher
ServiceProvider.java
private static OkHttpClient httpClient = new OkHttpClient.Builder()
...
.build();

15. Retrofit Refresher
ServiceProvider.java
private static Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(httpClient)
...
.build();

16. Retrofit Refresher
ServiceProvider.java
private static Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(httpClient)
...
.build();

17. Retrofit Refresher
ServiceProvider.java
private static Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(httpClient)
...
.build();

18. Retrofit Refresher
ServiceProvider.java
public static <S> S createService(Class<S> serviceClass) {
return retrofit.create(serviceClass);
}

19. Why is everything static in ServiceProvider.java?
•We want same configurations on each Service
•Alternatives:
A. Use Dependency Injection
B. Use Singleton

20. Make a Network Call
public class MainActivity extends AppCompatActivity {
private ColuService mColuService;
@Override
protected void onCreate(Bundle savedInstanceState) {
...
mColuService = ServiceProvider.createService(ColuService.class);
getBusinesses();
}

21. Make a Network Call
public class MainActivity extends AppCompatActivity {
private ColuService mColuService;
@Override
protected void onCreate(Bundle savedInstanceState) {
...
mColuService = ServiceProvider.createService(ColuService.class);
getBusinesses();
}

22. Make a Network Call
public class MainActivity extends AppCompatActivity {
private ColuService mColuService;
@Override
protected void onCreate(Bundle savedInstanceState) {
...
mColuService = ServiceProvider.createService(ColuService.class);
getBusinesses();
}

23. Make a Network Call
public class MainActivity extends AppCompatActivity {
private ColuService mColuService;
@Override
protected void onCreate(Bundle savedInstanceState) {
...
mColuService = ServiceProvider.createService(ColuService.class);
getBusinesses();
}

24. Make a Network Call
public class MainActivity extends AppCompatActivity {
private void getBusinesses() {
mColuService
.getBusinessesAroundMe(“AZ”, 20)
.enqueue(new Callback<List<Business>>() {
// ...
});

25. Make a Network Call
public class MainActivity extends AppCompatActivity {
.enqueue(new Callback<List<Business>>() {
@Override
public void onResponse(@NonNull Call<List<Business>> call,
@NonNull Response<List<Business>> response) {
// Check response
}
@Override
public void onFailure(@NonNull Call<List<Business>> call,
@NonNull Throwable t) {
}

26. Make a Network Call
public class MainActivity extends AppCompatActivity {
.enqueue(new Callback<List<Business>>() {
@Override
public void onResponse(@NonNull Call<List<Business>> call,
@NonNull Response<List<Business>> response) {
// Check response
}
@Override
public void onFailure(@NonNull Call<List<Business>> call,
@NonNull Throwable t) {
}

27. Make a Network Call
@Override
public void onResponse(@NonNull Call<List<Business>> call,
@NonNull Response<List<Business>> response) {
// Check response
if (response.code() == 200) {
// Do awesome stuff
} else {
// Handle other response codes
}
}

28. Status Codes
• 1xx - Informational Messages (Less useful)
• 2xx - Successful
• 3xx - Another action (i.e. Not Modified)
• 4xx - Client error (i.e. bad request)
• 5xx - Server error (i.e. requested resource was not found)

29. Questions?

31. ● It is style of software architecture
● Stands for REpresentational State Transfer
● Uses HTTP Protocol
● Can transfer any data
● Data often being transferred as JSON
REST

32. Endpoints Interface Abstraction
public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}

33. Colu Server
Businesses Table
business_id
[ {
"name": “….”
“location": “…”
…
Host (BASE_URL)
https://coluserver.com/

34. public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}
Logical Path to Data on Server

35. Colu Server
Businesses Table
business_id
[ {
"name": “….”
“location": “…”
…
Path
https://coluserver.com/businesses
Host (BASE_URL)

36. public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}
What to Do With Data

37. Colu Server
Businesses Table
business_id
[ {
"name": “….”
“location": “…”
…
Path
https://coluserver.com/businesses
Host (BASE_URL)Action Verb
GET

38. HTTP Action Verbs
HTTP ACTION VERB OPERATION MEANING
POST Create new resource in database
GET Retrieve data from database
PUT Update data in database
PATCH Partially update data in database
DELETE Delete data from database

39. public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}
What to Do With Data

40. Colu Server
Businesses Table
business_id
[ {
"name": “….”
“location": “…”
…
Path
https://coluserver.com/businesses?orderedBy=AZ&radius=20
Host (BASE_URL) Query ParamsAction Verb
GET

41. public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}
What to Do With Data

42. JSON to Java
public class Business {
private String id;
private String accountId;
private String name;
private String normalizedName;
...
{
"data": [
{
"id": "34o23i4jn23423",
"accountId": "eirjweorknwe93n54354",
"name": "blessed falafel",
"...": "..."
},
{
"...": "..."
}
],
"total": 5000,
"limit": 100,
"offset": 200,

43. Pro Tip - Use POJO Generator Plugins
i.e. RoboPOJOGenerator
https://github.com/robohorse/RoboPOJOGenerato
r

44. Create JSON Converter Factory
build.gradle
dependencies {
// Add Gson Converter
compile ‘com.squareup.retrofit2:converter-gson:2.8.5’
}

45. Add JSON Converter Factory
ServiceProvider.java
private static Retrofit.Builder builder =
new Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create());

46. public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}
What to Do With Data

47. Call object
• Call<List<Business>> - Retrofit will take the response body and try to
convert it to Java objects.
• Call<ResponseBody> - This makes the raw response payload available, but
skips the mapping to Java objects
• Call<Void> - Skips response

48. Download Large Files
Use @Streaming - It will tell Retrofit that instead of moving the entire file into memory, it'll pass
along the bytes right
@Streaming
@GET("/businesses")
Call<ResponseBody> getAllBusinessesInCountry(@Query("countryCode") String
countryCode);

49. Manipulate Call objects
public class MainActivity extends AppCompatActivity {
private Call<List<Business>> mGetBusinessesCall;
private void getBusinessesAroundMe() {
mGetBusinessesCall = mColuService.getBusinessesAroundMe(“AZ”, 20);
mGetBusinessesCall.enqueue(
new Callback<List<Business>>() {
…
}

50. Manipulate Call objects
public class MainActivity extends AppCompatActivity {
@Override
protected void onDestroy() {
super.onDestroy();
mGetBusinessesCall.cancel();
}

51. public interface ColuService {
@GET(“/businesses”)
@Headers("Content-Type: application/json")
Call<List<Business>> getBusinessesAroundMe(@Query("orderedBy") String orderedBy,
@Query("radius") int inRadius);
...
}
What to Do With Data

52. Headers == Request/Response MetaData
• Content-Type: application/json
• Authorization: <Your Token>
• Etag
• If-Modified-Since
• X-Api-Version
• X-WhatEverYouWant
• …

53. Print Request/Response

54. HttpLogging Interceptor
dependencies {
implementation "com.squareup.okhttp3:logging-interceptor:3.10.0"
}
build.gradle

55. Enable Http Logging
ServiceProvider.java
private static OkHttpClient.Builder httpClient =
new OkHttpClient.Builder()
...
.addInterceptor(new HttpLoggingInterceptor()
.setLevel(HttpLoggingInterceptor.Level.BODY));

56. Log Request in Logcat
**************************** REQUEST *******************************
Url: https://coluserver.com/businesses?orderedBy=AZ&radius=20
Method: GET
Headers:
content-type: application/json;
X-Colu-ApiVersion: 5
X-Colu-Device-Identifier: fc531e38666948e043c6ab...
Authorization: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9....
*************************** REQUEST END *******************

57. Response Log
***************************** RESPONSE *****************************
Code: 200
Headers:
date: Fri, 27 Jul 2018 07:24:44 GMT
content-type: application/json; charset=utf-8
...
etag: W/"b-EFAlOux7Kcr/ZEgGkn2r+oFAbu4"
Body:
{"businesses":[
{
"id":"aj28j..."
}
]}
***************************** RESPONSE END *****************************

58. Response Log
***************************** RESPONSE ******************
Code: 200
Headers:
date: Fri, 27 Jul 2018 07:24:44 GMT
content-type: application/json; charset=utf-8
...
etag: W/“b-EFAlOux7Kcr/ZEgGkn2r+oFAbu4"
Body:
{"businesses":[
{
"id":"aj28j..."
}
]}
***************************** RESPONSE END *************
Headers

59. Response Log
***************************** RESPONSE ******************
Code: 200
Headers:
date: Fri, 27 Jul 2018 07:24:44 GMT
content-type: application/json; charset=utf-8
...
etag: W/“b-EFAlOux7Kcr/ZEgGkn2r+oFAbu4"
Body:
{"businesses":[
{
"id":"aj28j..."
}
]}
***************************** RESPONSE END *************
Optional Body

60. private static HttpLoggingInterceptor loggingInterceptor =
new HttpLoggingInterceptor()
.setLevel(HttpLoggingInterceptor.Level.BODY);
private static OkHttpClient.Builder httpClient =
new OkHttpClient.Builder()
...
.addInterceptor(loggingInterceptor);
Enable Http Logging
ServiceProvider.java
?

61. Interceptors

62. Called Once
Application Interceptors

63. Multiple Calls
Network Interceptors

64. public class MyInterceptor implements Interceptor {
@Override
public Response intercept(@NonNull Chain chain) throws IOException {
}
}
Custom Interceptors Implementation

65. public class MyInterceptor implements Interceptor {
@Override
public Response intercept(@NonNull Chain chain) throws IOException {
}
}
Custom Interceptors Implementation

66. Custom Interceptor Use Case

67. Authentication Flow

68. Request Without Authorization
GET https://coluserver.com/businesses
401 Unauthorized

69. Get Authentication Token
{
"username": "artyom",
"password": "123456"
}
200 OK
{
"token": “437fh97b..”,
}
Save Token in
Storage
POST https://coluserver.com/login

70. Add Token To Each Request
200 OK + Response Body
Header Authorization: 437fh97b..
GET https://coluserver.com/businesses

71. @Override
public Response intercept(@NonNull Chain chain) throws IOException {
// Original Request
Request original = chain.request();
// Get previously saved Authentication token
String token = Storage.getInstance().getToken();
Add Token To Each Request - Right Way

72. @Override
public Response intercept(@NonNull Chain chain) throws IOException {
// Original Request
Request original = chain.request();
// Get previously saved Authentication token
String token = Storage.getInstance().getToken();
Add Token To Each Request - Right Way

73. @Override
public Response intercept(@NonNull Chain chain) throws IOException {
// Original Request
Request original = chain.request();
// Get previously saved Authentication token
String token = Storage.getInstance().getToken();
Add Token To Each Request - Right Way

74. @Override
public Response intercept(@NonNull Chain chain) throws IOException {
// Request customization: add request headers
Request.Builder requestBuilder = original.newBuilder()
.header("Authorization", token);
// Modified request
Request request = requestBuilder.build();
// Continue with request
return chain.proceed(request);
Add Token To Each Request - Right Way

75. @Override
public Response intercept(@NonNull Chain chain) throws IOException {
// Request customization: add request headers
Request.Builder requestBuilder = original.newBuilder()
.header("Authorization", token);
// Modified request
Request request = requestBuilder.build();
// Continue with request
return chain.proceed(request);
Add Token To Each Request - Right Way

76. @Override
public Response intercept(@NonNull Chain chain) throws IOException {
// Request customization: add request headers
Request.Builder requestBuilder = original.newBuilder()
.header("Authorization", token);
// Modified request
Request request = requestBuilder.build();
// Continue with request
return chain.proceed(request);
Add Token To Each Request - Right Way

77. ServiceProvider.java
private static OkHttpClient.Builder httpClient =
new OkHttpClient.Builder()
.connectTimeout(30, TimeUnit.SECONDS)
.readTimeout(30, TimeUnit.SECONDS)
.writeTimeout(30, TimeUnit.SECONDS)
// ...
// ...
.addInterceptor(new AuthenticationInterceptor()));
Add Token To Each Request - Right Way

78. Control Interceptors Functionality

79. Control Interceptors Functionality
public interface ColuService {
//. . .
@POST("/users/login")
@Headers("AppInternal-NoAuth:true")
Call<LoginResponse> login(@Body LoginRequest credentials);
}
The trick: Create fake headers to signal the Interceptors what to do

80. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Original Request
Request request = chain.request();
// if NoAuth-flag header is presenting, no authentication will be added
if (request.header("AppInternal-NoAuth") != null) {
// Remove internal header from request
request = request.newBuilder()
.removeHeader("AppInternal-NoAuth")
.build();
} else {

81. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Original Request
Request request = chain.request();
// if NoAuth-flag header is presenting, no authentication will be added
if (request.header("AppInternal-NoAuth") != null) {
// Remove internal header from request
request = request.newBuilder()
.removeHeader("AppInternal-NoAuth")
.build();
} else {

82. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Original Request
Request request = chain.request();
// if NoAuth-flag header is presenting, no authentication will be added
if (request.header("AppInternal-NoAuth") != null) {
// Remove internal header from request
request = request.newBuilder()
.removeHeader("AppInternal-NoAuth")
.build();
} else {

83. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Original Request
Request request = chain.request();
// if NoAuth-flag header is presenting, no authentication will be added
if (request.header("AppInternal-NoAuth") != null) {
// Remove internal header from request
request = request.newBuilder()
.removeHeader("AppInternal-NoAuth")
.build();
} else {

84. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Get previously saved Authentication token
String token = Storage.getInstance().getToken();
// Request customization: add request headers
request = request.newBuilder()
.header("Authorization", token)
.build();
}
// Continue with request
return chain.proceed(request);

85. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Get previously saved Authentication token
String token = Storage.getInstance().getToken();
// Request customization: add request headers
request = request.newBuilder()
.header("Authorization", token)
.build();
}
// Continue with request
return chain.proceed(request);

86. Check Internal Headers Within Interceptors
AuthenticationInterceptor.java
// Get previously saved Authentication token
String token = Storage.getInstance().getToken();
// Request customization: add request headers
request = request.newBuilder()
.header("Authorization", token)
.build();
}
// Continue with request
return chain.proceed(request);

87. Optimization

88. Use Cache

89. 200 OK
GET https://coluserver.com/businesses
{"businesses":[
{
"id":"aj28j..."
}…
]}
Use Cache

90. HTTP Cache Strategies
1. Etag/If-None-Match (HashCode based)
2. If-Modified-Since/Last-Modified (Timestamp basef)

91. Etag/If-None-Match
200 OK + Response Body
Header ETag: X
304 Not Modified (No body included)
Header If-None-Match: X
Cached response
Will be used
GET https://coluserver.com/businesses
GET https://coluserver.com/businesses

92. If-Modified-Since/Last-Modified
200 OK + Response Body
Header Last-Modified: X
304 Not Modified (No body included)
Header If-Modified-Since: X
Cached response
Will be used
GET https://coluserver.com/businesses
GET https://coluserver.com/businesses

93. Server Caching Configuration
• “Cache Control : no-store”
Disabled
Enabled, requires verification
Enabled, no need to verify during max-age
• “Cache Control : must-revalidate, max-age=120”
• “Cache Control : no-cache”

94. Enable Caching in Application
ServiceProvider.java
private static int cacheSize = 10 * 1024 * 1024; // 10 MB
private static Cache cache = new Cache(StorageUtils.
getCacheFolder(MyApplication.getAppContext()),
cacheSize);
private static OkHttpClient.Builder httpClient =
new OkHttpClient.Builder()
.cache(cache)
...

95. ServiceProvider.java
private static int cacheSize = 10 * 1024 * 1024; // 10 MB
private static Cache cache = new Cache(StorageUtils.
getCacheFolder(MyApplication.getAppContext()),
cacheSize);
private static OkHttpClient.Builder httpClient =
new OkHttpClient.Builder()
.cache(cache)
...
Enable Caching in Application

96. ServiceProvider.java
private static int cacheSize = 10 * 1024 * 1024; // 10 MB
private static Cache cache = new Cache(StorageUtils.
getCacheFolder(MyApplication.getAppContext()),
cacheSize);
private static OkHttpClient.Builder httpClient =
new OkHttpClient.Builder()
.cache(cache)
...
Enable Caching in Application

97. What Was Improved
1. Internet traffic saved
2. Faster response
3. Better experience + Cost savings

98. Explore More
• Future Studio Retrofit Tutorials -
https://futurestud.io/tutorials/retrofit-getting-started-and-android-client
• HTTP Caching by Ilya Grigorik -
https://developers.google.com/web/fundamentals/performance/optimizing-content-efficienc
y/http-caching

99. Questions?

100. Colu is Hiring! CV to artyom@colu.com
Daniel
Roi
Yehuda
Hi

101. Thank You!