Simple HTTP with Retrofit 2 (Droidcon NYC 2015)

Retrofit has been simplifying HTTP calls for years and this new version is no different. In addition to fixing some long-standing annoyances, there are a handful of new features which make it more powerful than ever.

This talk will focus on how the new APIs in Retrofit aid in making HTTP calls as simple as possible for your app. The integration with OkHttp and Okio APIs will be covered to ensure a full understanding of the HTTP stack. Common use-cases and design patterns through more advanced functionality will end the talk.

No prior Retrofit, OkHttp, or Okio exposure needed. The content may quickly cover or skip some introductory aspects in order to allow focus on more actionable and useful content.

Video: https://youtu.be/KIAoQbAu3eA

Transcript

1. Retrofit Two
   Jake Wharton
   

   View Slide

2. Retrofit 2 will be out
   by the end of this year
   " "
   — Naïve Man
   

   View Slide

3. Retrofit 2 will be out
   by the end of this year
   " "
   — Jake Wharton
   

   View Slide

4. Retrofit 2 will be out
   by the end of this year
   " "
   Droidcon NYC 2014
   — Jake Wharton
   

   View Slide

5. Retrofit 2 will be out
   by the end of this year
   " "
   Droidcon NYC 2015
   — Jake Wharton
   

   View Slide

6. Retrofit 1
   

   View Slide

7. Retrofit 1
   • Made open source on October 13th, 2010
   

   View Slide

8. Retrofit 1
   • Made open source on October 13th, 2010
   • Originally a Bob Lee joint
   

   View Slide

9. Retrofit 1
   • Made open source on October 13th, 2010
   • Originally a Bob Lee joint
   • Took over / stole stewardship mid-2012
   

   View Slide

10. Retrofit 1
    • Made open source on October 13th, 2010
    • Originally a Bob Lee joint
    • Took over / stole stewardship mid-2012
    • Released 1.0 on May 13th, 2013
    

    View Slide

11. Retrofit 1
    • Made open source on October 13th, 2010
    • Originally a Bob Lee joint
    • Took over / stole stewardship mid-2012
    • Released 1.0 on May 13th, 2013
    • 18 releases post-1.0 with tons of features / fixes
    

    View Slide

12. The Good
    

    View Slide

13. The Good
    • Interface service declarations
    • Method and parameter annotations customize request
    

    View Slide

14. Interface and annotations
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

15. The Good
    • Interface service declarations
    • Method and parameter annotations customize request
    • Pluggable HTTP client and serialization
    

    View Slide

16. Pluggable client and serialization
    builder.setClient(new UrlConnectionClient());
    builder.setClient(new ApacheClient());
    builder.setClient(new OkClient());
    

    View Slide

17. Pluggable client and serialization
    builder.setClient(new UrlConnectionClient());
    builder.setClient(new ApacheClient());
    builder.setClient(new OkClient());
    builder.setClient(new CustomClient());
    

    View Slide

18. Pluggable client and serialization
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

19. Pluggable client and serialization
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    builder.setConverter(new GsonConverter());
    builder.setConverter(new JacksonConverter());
    

    View Slide

20. Pluggable client and serialization
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    ContributorResponse repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

21. Pluggable client and serialization
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    ContributorResponse repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    builder.setConverter(new ProtoConverter());
    builder.setConverter(new WireConverter());
    

    View Slide

22. Pluggable client and serialization
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    ContributorResponse repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    builder.setConverter(new ProtoConverter());
    builder.setConverter(new WireConverter());
    builder.setConverter(new SimpleXMLConverter());
    

    View Slide

23. Pluggable client and serialization
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    ContributorResponse repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    builder.setConverter(new ProtoConverter());
    builder.setConverter(new WireConverter());
    builder.setConverter(new SimpleXMLConverter());
    builder.setConverter(new CustomConverter());
    

    View Slide

24. The Good
    • Interface service declarations
    • Method and parameter annotations customize request
    • Pluggable HTTP client and serialization
    • Synchronous, asynchronous, and RxJava execution
    

    View Slide

25. Sync, async, and RxJava
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    List contributors =
    gitHubService.repoContributors("square", "retrofit");
    

    View Slide

26. Sync, async, and RxJava
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    void repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo,

    Callback> cb);

    }
    service.repoContributors("square", "retrofit", new Callback>() {

    @Override void success(List contributors, Response response) {

    // ...

    }

    

    @Override void failure(RetrofitError error) {

    // ...

    }

    });
    

    View Slide

27. Sync, async, and RxJava
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    Observable> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    gitHubService.repoContributors("square", "retrofit")

    .subscribe(new Action1>() {

    @Override public void call(List contributors) {

    // ...

    }

    });
    

    View Slide

28. The Good
    • Interface service declarations
    • Method and parameter annotations customize request
    • Pluggable HTTP client and serialization
    • Synchronous, asynchronous, and RxJava execution
    

    View Slide

29. The Not-So-Good
    

    View Slide

30. The Not-So-Good
    • Request/Response (and friends) model classes
    

    View Slide

31. Request/Response model classes
    

    View Slide

32. The Not-So-Good
    • Request/Response (and friends) model classes
    • No access to serialized body and response data
    

    View Slide

33. No access to body and response
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }X
    

    View Slide

34. No access to body and response
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    @GET("/repos/{owner}/{repo}/contributors")

    Response repoContributors2(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }X
    

    View Slide

35. The Not-So-Good
    • Request/Response (and friends) model classes
    • No access to serialized body and response data
    • Rigid execution mechanisms
    

    View Slide

36. Rigid execution mechanisms
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);
    @GET("/repos/{owner}/{repo}/contributors")

    void repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo,

    Callback> cb);

    }
    

    View Slide

37. Rigid execution mechanisms
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    Observable> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

38. Rigid execution mechanisms
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    ListenableFuture> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

39. Rigid execution mechanisms
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    CompletableFuture> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

40. The Not-So-Good
    • Request/Response (and friends) model classes
    • No access to serialized body and response data
    • Rigid execution mechanisms
    • Inefficient converter usage
    

    View Slide

41. Inefficient converter usage
    interface Converter {

    Object fromBody(TypedInput body, Type type);

    TypedOutput toBody(Object object);

    }
    

    View Slide

42. Inefficient converter usage
    interface Converter {

    Object fromBody(TypedInput body, Type type);

    TypedOutput toBody(Object object);

    }
    Type
    TypeAdapter
    TypedInput/Output
    JsonAdapter
    ObjectReader/Writer
    Parser
    ProtoAdapter
    

    View Slide

43. Inefficient converter usage
    interface Converter {

    Object fromBody(TypedInput body, Type type);

    TypedOutput toBody(Object object);

    }
    Type
    TypeAdapter
    TypedInput/Output
    JsonAdapter
    ObjectReader/Writer
    Parser
    ProtoAdapter
    

    View Slide

44. The Not-So-Good
    • Request/Response (and friends) model classes
    • No access to serialized body and response data
    • Rigid execution mechanisms
    • Inefficient converter usage
    • Simple custom parameter types support
    

    View Slide

45. Simple custom parameter types
    interface GitHubService {

    @GET("/search/repositories")

    RepositoriesResponse searchRepos(

    @Query("q") String query,

    @Query("since") Date since);

    }X
    

    View Slide

46. Simple custom parameter types
    interface GitHubService {

    @GET("/search/repositories")

    RepositoriesResponse searchRepos(

    @Query("q") String query,

    @Query("since") Date since);

    }X
    /search/repositories?q=retrofit&since=2015-08-27
    

    View Slide

47. Simple custom parameter types
    interface GitHubService {

    @GET("/search/repositories")

    RepositoriesResponse searchRepos(

    @Query("q") String query,

    @Query("since") Date since);

    }X
    /search/repositories?q=retrofit&since=2015-08-27
    /search/repositories?q=retrofit&since=20150827
    

    View Slide

48. The Not-So-Good
    • Request/Response (and friends) model classes
    • No access to serialized body and response data
    • Rigid execution mechanisms
    • Inefficient converter usage
    • Simple custom parameter types support
    

    View Slide

49. Retrofit 2
    

    View Slide

50. Retrofit 2
    • Call encapsulates single request/response interaction
    

    View Slide

51. Call
    • Models a single request/response pair
    

    View Slide

52. Call
    • Models a single request/response pair
    • Separates request creation from response handling
    

    View Slide

53. Call
    • Models a single request/response pair
    • Separates request creation from response handling
    • Each instance can only be used once...
    

    View Slide

54. Call
    • Models a single request/response pair
    • Separates request creation from response handling
    • Each instance can only be used once...
    • ...instances can be cloned
    

    View Slide

55. Call
    • Models a single request/response pair
    • Separates request creation from response handling
    • Each instance can only be used once...
    • ...instances can be cloned
    • Supports both synchronous and asynchronous execution.
    

    View Slide

56. Call
    • Models a single request/response pair
    • Separates request creation from response handling
    • Each instance can only be used once...
    • ...instances can be cloned
    • Supports both synchronous and asynchronous execution.
    • Can be (actually) canceled
    

    View Slide

57. Call
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    List repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);
    }X
    

    View Slide

58. Call
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    Call> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }X
    

    View Slide

59. Call
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    Call> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    

    View Slide

60. Call
    interface GitHubService {

    @GET("/repos/{owner}/{repo}/contributors")

    Call> repoContributors(

    @Path("owner") String owner,

    @Path("repo") String repo);

    }
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    View Slide

61. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    View Slide

62. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    response = call.execute();
    

    View Slide

63. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    response = call.execute();
    // This will throw IllegalStateException:

    response = call.execute();
    

    View Slide

64. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    response = call.execute();
    // This will throw IllegalStateException:

    response = call.execute();
    Call> call2 = call.clone();

    // This will not throw:

    response = call2.execute();
    

    View Slide

65. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    View Slide

66. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    

    call.enqueue(new Callback>() {

    @Override void onResponse(/* ... */) {

    // ...

    }

    

    @Override void onFailure(Throwable t) {

    // ...

    }

    });
    

    View Slide

67. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    call.enqueue( );
    // or...
    call.execute();
    

    View Slide

68. Call
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    call.enqueue( );
    // or...
    call.execute();
    // later...
    call.cancel();
    

    View Slide

69. Retrofit 2
    • Call encapsulates single request/response interaction
    • Parameterized Response object
    

    View Slide

70. Response
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    response = call.execute();
    

    View Slide

71. Response
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    Response> response = call.execute();
    

    View Slide

72. Response
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    Response> response = call.execute();
    

    View Slide

73. Response
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    call.enqueue(new Callback>() {

    @Override void onResponse(/* ... */) {

    // ...

    }X

    

    @Override void failure(Throwable t) {

    // ...

    }X

    });
    

    View Slide

74. Response
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    call.enqueue(new Callback>() {

    @Override void onResponse(Response> response) {

    // ...

    }X

    

    @Override void failure(Throwable t) {

    // ...

    }X

    });
    

    View Slide

75. Response
    Call> call =
    gitHubService.repoContributors("square", "retrofit");
    call.enqueue(new Callback>() {

    @Override void onResponse(Response> response) {

    // ...

    }

    

    @Override void failure(Throwable t) {

    // ...

    }

    });
    

    View Slide

76. Response
    class Response {

    }X
    

    View Slide

77. Response
    class Response {

    int code();

    String message();
    Headers headers();

    }X
    

    View Slide

78. Response
    class Response {

    int code();

    String message();
    Headers headers();

    

    boolean isSuccess();

    }X
    

    View Slide

79. Response
    class Response {

    int code();

    String message();
    Headers headers();

    

    boolean isSuccess();
    T body();

    ResponseBody errorBody();

    }X
    

    View Slide

80. Response
    class Response {

    int code();

    String message();
    Headers headers();

    

    boolean isSuccess();
    T body();

    ResponseBody errorBody();
    com.squareup.okhttp.Response raw();

    }X
    

    View Slide

81. Retrofit 2
    • Call encapsulates single request/response interaction
    • Parameterized Response object
    

    View Slide

82. If it isn't broken...
    

    View Slide

83. Fixed Query Param
    interface SomeService {

    @GET("/some/endpoint?fixed=query")

    Call someEndpoint();

    }
    someService.someEndpoint();
    // GET /some/endpoint?fixed=query HTTP/1.1
    

    View Slide

84. Dynamic Query Param
    interface SomeService {

    @GET("/some/endpoint")

    Call someEndpoint(

    @Query("dynamic") String dynamic);

    }
    someService.someEndpoint("query");
    // GET /some/endpoint?dynamic=query HTTP/1.1
    

    View Slide

85. Dynamic Query Param Map
    interface SomeService {

    @GET("/some/endpoint")

    Call someEndpoint(

    @QueryMap Map dynamic);

    }
    someService.someEndpoint(
    Collections.singletonMap("dynamic", "query"));
    // GET /some/endpoint?dynamic=query HTTP/1.1
    

    View Slide

86. Omit Dynamic Query Param
    interface SomeService {

    @GET("/some/endpoint")

    Call someEndpoint(

    @Query("dynamic") String dynamic);

    }
    someService.someEndpoint(null);
    // GET /some/endpoint HTTP/1.1
    

    View Slide

87. Fixed+Dynamic Query Params
    interface SomeService {

    @GET("/some/endpoint?fixed=query")

    Call someEndpoint(

    @Query("dynamic") String dynamic);

    }
    someService.someEndpoint("query");
    // GET /some/endpoint?fixed=query&dynamic=query HTTP/1.1
    

    View Slide

88. Path Replacement
    interface SomeService {

    @GET("/some/endpoint/{foo}")

    Call someEndpoint(

    @Path("thing") String thing);

    }
    someService.someEndpoint("bar");
    // GET /some/endpoint/bar HTTP/1.1
    

    View Slide

89. Fixed Header
    interface SomeService {

    @GET("/some/endpoint")
    @Headers("Accept-Encoding: application/json")

    Call someEndpoint();

    }
    someService.someEndpoint();
    // GET /some/endpoint HTTP/1.1
    // Accept-Encoding: application/json
    

    View Slide

90. Dynamic Header
    interface SomeService {

    @GET("/some/endpoint")

    Call someEndpoint(
    @Header("Location") String location);

    }
    someService.someEndpoint("Droidcon NYC 2015");
    // GET /some/endpoint HTTP/1.1
    // Location: Droidcon NYC 2015
    

    View Slide

91. Omit Dynamic Header
    interface SomeService {

    @GET("/some/endpoint")

    Call someEndpoint(
    @Header("Location") String location);

    }
    someService.someEndpoint(null);
    // GET /some/endpoint HTTP/1.1
    

    View Slide

92. Fixed+Dynamic Header
    interface SomeService {

    @GET("/some/endpoint")
    @Headers("Accept-Encoding: application/json")

    Call someEndpoint(
    @Header("Location") String location);

    }
    someService.someEndpoint("Droidcon NYC 2015");
    // GET /some/endpoint HTTP/1.1
    // Accept-Encoding: application/json
    // Location: Droidcon NYC 2015
    

    View Slide

93. Post Without Body
    interface SomeService {

    @POST("/some/endpoint")

    Call someEndpoint();

    }
    someService.someEndpoint();
    // POST /some/endpoint?fixed=query HTTP/1.1
    // Content-Length: 0
    

    View Slide

94. Post With Body
    interface SomeService {

    @POST("/some/endpoint")

    Call someEndpoint(
    @Body SomeRequest body);

    }
    someService.someEndpoint();
    // POST /some/endpoint HTTP/1.1
    // Content-Length: 3
    // Content-Type: greeting
    //
    // Hi!
    

    View Slide

95. Form Encoded Fields
    interface SomeService {

    @FormUrlEncoded
    @POST("/some/endpoint")

    Call someEndpoint(
    @Field("name1") String name1,
    @Field("name2") String name2);

    }
    someService.someEndpoint("value1", "value2");
    // POST /some/endpoint HTTP/1.1
    // Content-Length: 25
    // Content-Type: application/x-www-form-urlencoded
    //
    // name1=value1&name2=value2
    

    View Slide

96. Omit Form Encoded Field
    interface SomeService {

    @FormUrlEncoded
    @POST("/some/endpoint")

    Call someEndpoint(
    @Field("name1") String name1,
    @Field("name2") String name2);

    }
    someService.someEndpoint("value1", null);
    // POST /some/endpoint HTTP/1.1
    // Content-Length: 12
    // Content-Type: application/x-www-form-urlencoded
    //
    // name1=value1
    

    View Slide

97. Form Encoded Field Map
    interface SomeService {

    @FormUrlEncoded
    @POST("/some/endpoint")

    Call someEndpoint(
    @FieldMap Map names);

    }
    someService.someEndpoint(
    ImmutableMap.of("name1", "value1", "name2", "value2"));
    // POST /some/endpoint HTTP/1.1
    // Content-Length: 25
    // Content-Type: application/x-www-form-urlencoded
    //
    // name1=value1&name2=value2
    

    View Slide

98. Multipart Parts
    interface SomeService {

    @Multipart
    @POST("/some/endpoint")

    Call someEndpoint(
    @Part("name1") String name1,
    @Part("name2") String name2);

    }
    someService.someEndpoint("value1", "value2");
    // POST /some/endpoint HTTP/1.1
    // Content-Length: 102
    // Content-Type: application/form-data
    //
    // ...
    

    View Slide

99. Omit Multipart Part
    interface SomeService {

    @Multipart
    @POST("/some/endpoint")

    Call someEndpoint(
    @Part("name1") String name1,
    @Part("name2") String name2);

    }
    someService.someEndpoint("value1", null);
    // POST /some/endpoint HTTP/1.1
    // Content-Length: 56
    // Content-Type: application/form-data
    //
    // ...
    

    View Slide

100. Multipart Part Map
     interface SomeService {

     @Multipart
     @POST("/some/endpoint")

     Call someEndpoint(
     @PartMap Map names);

     }
     someService.someEndpoint(
     ImmutableMap.of("name1", "value1", "name2", "value2"));
     // POST /some/endpoint HTTP/1.1
     // Content-Length: 102
     // Content-Type: application/form-data
     //
     // ...
     

     View Slide

101. If it isn't broken...
     

     View Slide

102. Retrofit 2
     • Call encapsulates single request/response interaction
     • Parameterized Response object
     • Dynamic URL parameter
     

     View Slide

103. Dynamic URL
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     

     View Slide

104. Dynamic URL
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     Call> call =
     gitHubService.repoContributors("square", "retrofit");
     Response> response = call.execute();
     

     View Slide

105. Dynamic URL
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     Call> call =
     gitHubService.repoContributors("square", "retrofit");
     Response> response = call.execute();
     // HTTP/1.1 200 OK
     // Link: page=2>; rel="next", contributors?page=3>; rel="last"
     // ...
     

     View Slide

106. Dynamic URL
     Response> response = call.execute();
     // HTTP/1.1 200 OK
     // Link: page=2>; rel="next", contributors?page=3>; rel="last"
     // ...
     

     View Slide

107. Dynamic URL
     Response> response = call.execute();
     // HTTP/1.1 200 OK
     // Link: page=2>; rel="next", contributors?page=3>; rel="last"
     // ...
     String links = response.headers().get("Link");
     

     View Slide

108. Dynamic URL
     Response> response = call.execute();
     // HTTP/1.1 200 OK
     // Link: page=2>; rel="next", contributors?page=3>; rel="last"
     // ...
     String links = response.headers().get("Link");
     String nextLink = nextFromGitHubLinks(links);
     

     View Slide

109. Dynamic URL
     Response> response = call.execute();
     // HTTP/1.1 200 OK
     // Link: page=2>; rel="next", contributors?page=3>; rel="last"
     // ...
     String links = response.headers().get("Link");
     String nextLink = nextFromGitHubLinks(links);
     // https://api.github.com/repositories/892275/contributors?page=2
     

     View Slide

110. Dynamic URL
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }X
     

     View Slide

111. Dynamic URL
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);
     

     @GET

     Call> repoContributorsPaginate(

     @Url String url);

     }X
     

     View Slide

112. Dynamic URL
     String nextLink = nextFromGitHubLinks(links);
     // https://api.github.com/repositories/892275/contributors?page=2
     

     View Slide

113. Dynamic URL
     String nextLink = nextFromGitHubLinks(links);
     // https://api.github.com/repositories/892275/contributors?page=2
     Call> nextCall =
     gitHubService.repoContributorsPaginate(nextLink);
     

     View Slide

114. Retrofit 2
     • Call encapsulates single request/response interaction
     • Parameterized Response object
     • Dynamic URL parameter
     • Multiple, efficient converters
     

     View Slide

115. Converters
     interface SomeProtoService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     }X
     interface SomeJsonService {

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     

     View Slide

116. Converters
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     

     

     SomeProtoResponse
     

     View Slide

117. Converters
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     SomeProtoResponse
     

     View Slide

118. Converters
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     SomeProtoResponse Proto? Yes!
     

     View Slide

119. Converters
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     SomeJsonResponse
     

     View Slide

120. Converters
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     SomeJsonResponse Proto? No!
     

     View Slide

121. Converters
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     SomeJsonResponse Proto? No! JSON? Yes!
     

     View Slide

122. Retrofit 2
     • Call encapsulates single request/response interaction
     • Parameterized Response object
     • Dynamic URL parameter
     • Multiple, efficient converters
     • Multiple, pluggable execution mechanisms
     

     View Slide

123. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }X
     

     View Slide

124. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(

     @Path("owner") String owner,

     @Path("repo") String repo);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }X
     

     View Slide

125. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Call
     

     View Slide

126. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Call
     

     View Slide

127. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Call RxJava? No!
     

     View Slide

128. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Call RxJava? No! Call? Yes!
     

     View Slide

129. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Observable
     

     View Slide

130. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Observable RxJava? Yes!
     

     View Slide

131. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Future
     

     View Slide

132. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Future RxJava? No!
     

     View Slide

133. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Future RxJava? No! Call? No!
     

     View Slide

134. Execution Mechanisms
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Future> repoContributors3(..);

     }X
     Future RxJava? No! Call? No! Throw!
     

     View Slide

135. Retrofit 2
     • Call encapsulates single request/response interaction
     • Parameterized Response object
     • Dynamic URL parameter
     • Multiple, efficient converters
     • Multiple, pluggable execution mechanisms
     

     View Slide

136. Powered by OkHttp
     

     View Slide

137. Powered by OkHttp
     • In 2012 we needed client abstractions.
     

     View Slide

138. Powered by OkHttp
     • In 2012 we needed client abstractions.
     • In 2012 we needed request/response abstractions.
     

     View Slide

139. Powered by OkHttp
     • In 2012 we needed client abstractions.
     • In 2012 we needed request/response abstractions.
     • In 2012 we needed header abstractions.
     

     View Slide

140. Powered by OkHttp
     • In 2012 we needed client abstractions.
     • In 2012 we needed request/response abstractions.
     • In 2012 we needed header abstractions.
     • It's 2015. OkHttp is small, lean, focused, and full-featured.
     

     View Slide

141. Powered by OkHttp
     

     View Slide

142. Powered by OkHttp & Okio
     bit.ly/ok-libs
     

     View Slide

143. Retrofit
     

     View Slide

144. Retrofit OkHttp
     

     View Slide

145. Retrofit OkHttp
     Socket
     

     View Slide

146. Retrofit OkHttp
     BufferedSource
     BufferedSink
     Socket
     

     View Slide

147. Retrofit OkHttp
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     Socket
     

     View Slide

148. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     Socket
     

     View Slide

149. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     Socket
     Moshi
     

     View Slide

150. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     Socket
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

151. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     RequestBody
     ResponseBody
     Socket
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

152. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

153. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

154. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

155. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

156. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

157. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

158. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

159. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

160. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

161. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

162. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

163. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

164. Retrofit OkHttp
     MoshiConverter
     BufferedSource
     BufferedSink
     RequestBody
     ResponseBody
     
     MyService
     RequestBody
     ResponseBody
     Socket
     execute()
     myEndpoint()
     Moshi
     BufferedSink
     BufferedSource
     
     

     View Slide

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

     View Slide

166. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     

     View Slide

167. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     GitHubService gitHubService = retrofit.create(GitHubService.class);
     

     View Slide

168. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     // https://api.github.com/repos/square/retrofit/contributors
     

     View Slide

169. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     // https://api.github.com/repos/square/retrofit/contributors
     HttpUrl
     

     View Slide

170. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     // https://api.github.com/repos/square/retrofit/contributors
     HttpUrl
     .resolve()
     

     View Slide

171. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     

     View Slide

172. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     

     View Slide

173. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     

     View Slide

174. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     // https://api.github.com/repos/square/retrofit/contributors
     

     View Slide

175. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     // https://api.github.com/repos/square/retrofit/contributors
     HttpUrl
     .resolve()
     

     View Slide

176. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }X
     

     View Slide

177. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }X
     

     View Slide

178. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     

     View Slide

179. Setup
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com/v3/")
     .build();
     interface GitHubService {

     @GET("repos/{owner}/{repo}/contributors")

     Call> repoContributors(

     @Path("owner") String owner,

     @Path("repo") String repo);

     }
     // https://api.github.com/v3/repos/square/retrofit/contributors
     

     View Slide

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

     View Slide

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

     View Slide

182. Setup
     OkHttpClient client = new OkHttpClient();
     client.interceptors().add(..);
     Retrofit retrofit = new Retrofit.Builder()
     .baseUrl("https://api.github.com")
     .client(client)
     .build();
     

     View Slide

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

     View Slide

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

     View Slide

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

     View Slide

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

     View Slide

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

     View Slide

188. Extensibility
     • Converter.Factory
     • CallAdapter.Factory
     

     View Slide

189. Converter.Factory
     interface SomeService {

     @GET("/some/proto/endpoint")

     Call someProtoEndpoint();
     

     @GET("/some/json/endpoint")

     Call someJsonEndpoint();

     }X
     SomeJsonResponse Proto? No! JSON? Yes!
     

     View Slide

190. Converter.Factory
     interface Converter {
     interface Factory {
     Converter> create(Type type);
     }
     }X
     SomeJsonResponse Proto? No! JSON? Yes!
     

     View Slide

191. Converter.Factory
     SomeJsonResponse Proto? No! JSON? Yes!
     

     View Slide

192. Converter.Factory
     class ProtoConverterFactory {
     Converter> create(Type type);
     }X
     SomeJsonResponse
     null No!
     JSON? Yes!
     

     View Slide

193. JSON
     Converter.Factory
     class ProtoConverterFactory {
     Converter> create(Type type);
     }X
     SomeJsonResponse
     null No!
     Converter> Yes!
     class GsonConverterFactory {
     Converter> create(Type type);
     }X
     

     View Slide

194. Converter.Factory
     interface Converter {
     interface Factory {
     Converter> create(Type type);
     }X
     }X
     

     View Slide

195. Converter.Factory
     interface Converter {
     interface Factory {
     Converter> create(Type type);
     }X
     T fromBody(ResponseBody body);
     RequestBody toBody(T value);
     }X
     

     View Slide

196. Extensibility
     • Converter.Factory
     • CallAdapter.Factory
     

     View Slide

197. CallAdapter.Factory
     interface GitHubService {

     @GET("/repos/{owner}/{repo}/contributors")

     Call> repoContributors(..);
     

     @GET("/repos/{owner}/{repo}/contributors")

     Observable> repoContributors2(..);

     }X
     Call RxJava? No! Call? Yes!
     

     View Slide

198. CallAdapter.Factory
     interface CallAdapter {
     interface Factory {
     CallAdapter> create(Type type);
     }

     }X
     Call RxJava? No! Call? Yes!
     

     View Slide

199. CallAdapter.Factory
     Call RxJava? No! Call? Yes!
     

     View Slide

200. CallAdapter.Factory
     Call Call? Yes!
     class RxJavaCallAdapterFactory {
     CallAdapter> create(Type type);
     }X
     null No!
     

     View Slide

201. CallAdapter.Factory
     Call
     class RxJavaCallAdapterFactory {
     CallAdapter> create(Type type);
     }X
     null No!
     JSON
     CallAdapter> Yes!
     class CallAdapterFactory {
     CallAdapter> create(Type type);
     }X
     

     View Slide

202. CallAdapter.Factory
     interface CallAdapter {
     interface Factory {
     CallAdapter> create(Type type);
     }X
     }X
     

     View Slide

203. CallAdapter.Factory
     interface CallAdapter {
     interface Factory {
     CallAdapter> create(Type type);
     }X
     Type responseType();
     Object adapt(Call value);
     }X
     

     View Slide

204. Extensibility
     • Converter.Factory
     • CallAdapter.Factory
     

     View Slide

205. Under Construction
     

     View Slide

206. Under Construction
     • Parameter handlers
     

     View Slide

207. Under Construction
     • Parameter handlers
     • Logging?
     

     View Slide

208. Under Construction
     • Parameter handlers
     • Logging?
     • Finalizing mock module
     

     View Slide

209. Under Construction
     • Parameter handlers
     • Logging?
     • Finalizing mock module
     • Documentation
     

     View Slide

210. Under Construction
     • Parameter handlers
     • Logging?
     • Finalizing mock module
     • Documentation
     • WebSockets! (in v2.1)
     

     View Slide

211. Release?
     

     View Slide

212. Release?
     dependencies {

     compile 'com.squareup.retrofit:retrofit:2.0.0-beta1'
     compile 'com.squareup.retrofit:converter-gson:2.0.0-beta1'
     compile 'com.squareup.retrofit:adapter-rxjava:2.0.0-beta1'
     }
     

     View Slide

213. jakewharton
     jakewharton
     twitter.com/
     google.com/+
     .com
     Retrofit Two
     jakewharton
     

     View Slide