Retrofit is a library by Square that simplifies the process of converting REST APIs into Java interfaces. It supports easy serialization and deserialization of JSON through Gson, and allows both synchronous and asynchronous API calls using annotations. Additionally, Retrofit can be customized with converters and clients to handle specific data types and request headers.

1. Retrofit
* Released by Square.
* Retrofit turns your REST API into a Java interface.
* Offers very easy to use REST API Solution.

2. Retrofit Performance Analysis

3. Retrofit uses these library
lOkHttp
lGSON
lRxJava

4. GSON
lConversion of an object to json or from json to object.
lAll the fields by default are included in conversions even
private fields
lIf don’t want to include the field in conversion, use
transient modifier for that field

5. GSON Implementation
* This is a class for Person-
public class Person {
public String id;
@SerializedName(user_name)
public String name;
public Person parent;
//setter getter here
}
Obtains result like this

6. GSON Implementation

7. GSON Serialization
class PersonSerializer implements
JsonSerializer<Person> {
public JsonElement serialize(final Person person, Type
type,JsonSerializationContext context) {
JsonObject result = new JsonObject();
result.add("id", new JsonPrimitive(person.getId()));
result.add("name", new
JsonPrimitive(person.getName()));
Person parent = person.getParent();
if (parent != null) {

8. RxJava

9. Reactive Programming

10. Reactive Programming

11. Reactive Programming

12. Retrofit
1-Create Interface for API and declare methods for each
REST Call
2-Specify method type Using Annotations-
@GET,@POST,@PUT
3-For paramenters use -
@Path,@Query,@Body
4-Use RestAdapter to build the service client.

13. Retrofit Interface
public interface TestService {
@GET("/users/{user}/person")
List<Person> listPerson(@Path("user") String user);
}
RestAdapter restAdapter = new RestAdapter.Builder()
.setEndpoint("https://api.test.com")
.build();
TestService service =
restAdapter.create(TestService.class);

14. Interface's Methods
lA method with a return type will be executed
synchronously.
lAsynchronous execution requires the last parameter of the
method be a Callback.
l Using RxJava we can have return type as Observable

15. Interface's Methods
lPublic interface TestInterface{
@GET("/users/list")
Photo userList(); //Synchronous call
@POST("/users/list")
void userList(@Body User ,Callback<TResponse> cb);
//Asynchronous call
@GET("/users/list")
Observable<TResponse> userList();//Observable

16. HEADER MANIPULATION
lSet static headers for a method using
l@Headers("Cache-Control: max-age=640000")
lUse when need to send same header for all api-
lRequestInterceptor requestInterceptor = new
RequestInterceptor() {
l @Override
l public void intercept(RequestFacade request) {
l request.addHeader("User-Agent", "Retrofit-Sample-
App");

17. Retrofit Implementation
* Retrofit uses Gson by default to convert HTTP bodies to
and from JSON.
* Custom GSON Converter Example
If you want to specify behavior that is different from
Gson's defaults.
GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(MyType2.class, new
MyTypeAdapter());

18. Retrofit Implementation
* Create gson object this way-
Gson gson = new
GsonBuilder().registerTypeAdapter(Person.class, new
PersonSerializer())
.create();
* Pass this object to .setConverter
RestAdapter restAdapter = new RestAdapter.Builder()
.setEndpoint("https://api.github.com")
.setConverter(new GsonConverter(gson))

19. RestAdapter
*Using RestAdapter Object we initialize Interface
reference or service client.
* It has static class RestAdapter.Builder.
methods inside RestAdapter.Builder class-
*setEndpoint-API endpoint URL
*setClient-The HTTP client used for requests
*setRequestInterceptor-for adding Header/data to every
request.
setConverter-converter used for serialization and

20. Retrofit Implementation
* RestAdapter.Builder()
.setEndpoint(“http://www.githubservice.com”)
.setClient(new OkClient(okHttpClientWithCache()))
.setConverter(new GsonConverter(new
GsonBuilder().registerTypeAdapter(Test.class, new
TestDeserializer())
.build()
.create(TestInterface.class);

21. Retrofit Implementation
* Use http://www.jsonschema2pojo.org/ to create POJO
classes. Lets take this example-
{
"weather":[
{
"id":711,
"main":"Smoke",
"description":"smoke",
"icon":"50n"

22. Retrofit Implementation

23. Implementaion
* It Shows how to use SimpleXMLConverter to
communicate with an API that uses XML
RestAdapter restAdapter = new RestAdapter.Builder()
.setEndpoint("https://api.soundcloud.com")
.setConverter(new SimpleXMLConverter())
.build();
TestInterrface service =
restAdapter.create(TestInterface.class);

24. THANK YOU
l

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