Retrofit A type-safe HTTP client for Android and Java

Introduction

Retrofit turns your HTTP API into a Java interface.

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

The

Retrofit

class generates an implementation of the

GitHubService

interface.

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

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

Each

Call

from the created

GitHubService

can make a synchronous or asynchronous HTTP request to the remote webserver.

Call<List<Repo>> repos = service.listRepos("octocat");

Use annotations to describe the HTTP request:

URL parameter replacement and query parameter support
Object conversion to request body (e.g., JSON, protocol buffers)
Multipart request body and file upload
Note: This site is still in the process of being expanded for the new 2.0 APIs.

API Declaration

Annotations on the interface methods and its parameters indicate how a request will be handled.

Request Method

Every method must have an HTTP annotation that provides the request method and relative URL. There are five built-in annotations:

GET

,

POST

,

PUT

,

DELETE

, and

HEAD

. The relative URL of the resource is specified in the annotation.

@GET("users/list")

You can also specify query parameters in the URL.

@GET("users/list?sort=desc")

URL Manipulation

A request URL can be updated dynamically using replacement blocks and parameters on the method. A replacement block is an alphanumeric string surrounded by

{

and

}

. A corresponding parameter must be annotated with

@Path

using the same string.

@GET("group/{id}/users")
Call<List<User>> groupList(@Path("id") int groupId);

Query parameters can also be added.

@GET("group/{id}/users")
Call<List<User>> groupList(@Path("id") int groupId, @Query("sort") String sort);

For complex query parameter combinations a

Map

can be used.

@GET("group/{id}/users")
Call<List<User>> groupList(@Path("id") int groupId, @QueryMap Map<String, String> options);

Request Body

An object can be specified for use as an HTTP request body with the

@Body

annotation.

@POST("users/new")
Call<User> createUser(@Body User user);

The object will also be converted using a converter specified on the

Retrofit

instance. If no converter is added, only

RequestBody

can be used.

Form Encoded and Multipart

Methods can also be declared to send form-encoded and multipart data.

Form-encoded data is sent when

@FormUrlEncoded

is present on the method. Each key-value pair is annotated with

@Field

containing the name and the object providing the value.

@FormUrlEncoded
@POST("user/edit")
Call<User> updateUser(@Field("first_name") String first, @Field("last_name") String last);

Multipart requests are used when

@Multipart

is present on the method. Parts are declared using the

@Part

annotation.

@Multipart
@PUT("user/photo")
Call<User> updateUser(@Part("photo") RequestBody photo, @Part("description") RequestBody description);

Multipart parts use one of

Retrofit

's converters or they can implement

RequestBody

to handle their own serialization.

Header Manipulation

You can set static headers for a method using the

@Headers

annotation.

@Headers("Cache-Control: max-age=640000")
@GET("widget/list")
Call<List<Widget>> widgetList();

@Headers({
"Accept: application/vnd.github.v3.full+json",
"User-Agent: Retrofit-Sample-App"
})
@GET("users/{username}")
Call<User> getUser(@Path("username") String username);

Note that headers do not overwrite each other. All headers with the same name will be included in the request.

A request Header can be updated dynamically using the

@Header

annotation. A corresponding parameter must be provided to the

@Header

. If the value is null, the header will be omitted. Otherwise,

toString

will be called on the value, and the result used.

@GET("user")
Call<User> getUser(@Header("Authorization") String authorization)

Headers that need to be added to every request can be specified using anOkHttp interceptor.

Synchronous vs. Asynchronous

Call

instances can be executed either synchronously or asynchronously. Each instance can only be used once, but calling

clone()

will create a new instance that can be used.

On Android, callbacks will be executed on the main thread. On the JVM, callbacks will happen on the same thread that executed the HTTP request.

Retrofit Configuration

Retrofit

is the class through which your API interfaces are turned into callable objects. By default, Retrofit will give you sane defaults for your platform but it allows for customization.

Converters

By default, Retrofit can only deserialize HTTP bodies into OkHttp's

ResponseBody

type and it can only accept its

RequestBody

type for

@Body

.

Converters can be added to support other types. Six sibling modules adapt popular serialization libraries for your convenience.

Gson:

com.squareup.retrofit2:converter-gson

Jackson:

com.squareup.retrofit2:converter-jackson

Moshi:

com.squareup.retrofit2:converter-moshi

Protobuf:

com.squareup.retrofit2:converter-protobuf

Wire:

com.squareup.retrofit2:converter-wire

Simple XML:

com.squareup.retrofit2:converter-simplexml

Scalars (primitives, boxed, and String):

com.squareup.retrofit2:converter-scalars

Here's an example of using the

GsonConverterFactory

class to generate an implementation of the

GitHubService

interface which uses Gson for its deserialization.

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

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

Custom Converters

If you need to communicate with an API that uses a content-format that Retrofit does not support out of the box (e.g. YAML, txt, custom format) or you wish to use a different library to implement an existing format, you can easily
create your own converter. Create a class that extends the

Converter.Factory

class and pass in an instance when building your adapter.

Download

↓Latest JAR

The source code to the Retrofit, its samples, and this website isavailable on GitHub.

Maven

<dependency>
<groupId>com.squareup.retrofit2</groupId>
<artifactId>retrofit</artifactId>
<version>(insert latest version)</version>
</dependency>

Gradle

compile 'com.squareup.retrofit2:retrofit:(insert latest version)'

Retrofit requires at minimum Java 7 or Android 2.3.

ProGuard

If you are using Proguard in your project add the following lines to your configuration:

# Platform calls Class.forName on types which do not exist on Android to determine platform.
-dontnote retrofit2.Platform
# Platform used when running on RoboVM on iOS. Will not be used at runtime.
-dontnote retrofit2.Platform$IOS$MainThreadExecutor
# Platform used when running on Java 8 VMs. Will not be used at runtime.
-dontwarn retrofit2.Platform$Java8
# Retain generic type information for use by reflection by converters and adapters.
-keepattributes Signature
# Retain declared checked exceptions for use by a Proxy instance.
-keepattributes Exceptions

Contributing

If you would like to contribute code you can do so through GitHub by forking the repository and sending a pull request.

When submitting code, please make every effort to follow existing conventions and style in order to keep the code as readable as possible. Please also make sure your code compiles by running

mvn clean verify

.

Before your code can be accepted into the project you must also sign theIndividual Contributor License Agreement (CLA).

from:https://github.com/square/retrofit/blob/master/website/index.html