Dependency Injection with Dagger 2 (Devoxx 2014)

dependency injection with
Dagger 2
Jake Wharton

View Slide

Dependency Injection
flickr.com/photos/sunsetnoir/6984108500

View Slide

• No “new”, dependencies come to you
flickr.com/photos/sunsetnoir/6984108500

View Slide

• First and foremost a pattern

View Slide

• Every single app has some form of dependency injection

View Slide

Tweeter

View Slide

Twitter API
Tweeter

View Slide

Twitter API
Tweeter HTTP Client

View Slide

public class Tweeter { 
public void tweet(String tweet) { 
TwitterApi api = new TwitterApi(); 
api.postTweet("JakeWharton", tweet); 
} 
}

View Slide

} 
}
public class TwitterApi { 
public void postTweet(String user, String tweet) { 
OkHttpClient client = new OkHttpClient(); 
Request request = // TODO build POST request... 
client.newCall(request).execute(); 
} 
}

View Slide

} 
}
} 
}
Tweeter tweeter = new Tweeter(); 
tweeter.tweet("Hello, #Devoxx 2014!");

View Slide

} 
}

View Slide

private final OkHttpClient client = new OkHttpClient(); 
 
} 
}

View Slide

private final OkHttpClient client; 
 
public TwitterApi(OkHttpClient client) { 
this.client = client; 
} 
 
} 
}

View Slide

}
}

View Slide

TwitterApi api = new TwitterApi(new OkHttpClient()); 
} 
}

View Slide

private final TwitterApi api = new TwitterApi(new OkHttpClient()); 
 
} 
}

View Slide

private final String user; 
 
public Tweeter(String user) { 
this.user = user; 
} 
 
api.postTweet(user, tweet); 
} 
}

View Slide

Tweeter tweeter = new Tweeter(); 

View Slide

Tweeter tweeter = new Tweeter("JakeWharton"); 

View Slide

!
 
tweeter.tweet("#Hungover #Dagger");
!
 
tweeter.tweet("Waffles, beer, diamonds, chocolate, and Dagger!");
!
 
!
tweeter.tweet("Java Posse ain’t got nothing on #Dagger");
!
 
!
!
tweeter.tweet("Are these the same slides from last year? #meta");
!
 
!
!
!
tweeter.tweet("I need an injection of beer, amirite? #Dagger");

View Slide

!
 
tweeter.tweet("#Hungover #Dagger");
!
 
tweeter.tweet("Waffles, beer, diamonds, chocolate, and Dagger!");
!
 
!
tweeter.tweet("Java Posse ain’t got nothing on #Dagger");
!
 
!
!
tweeter.tweet("Are these the same slides from last year? #meta");
!
 
!
!
!
tweeter.tweet("I need an injection of beer, amirite? #Dagger");
Timeline timeline = new Timeline("JakeWharton"); 
timeline.loadMore(20); 
for (Tweet tweet : timeline.get()) { 
System.out.println(tweet); 
}

View Slide

public class Timeline { 
private final List cache = new ArrayList<>(); 
 
public Timeline(String user) { 
} 
 
public List get() { /* ... */ } 
public void loadMore(int amount) { /* ... */ } 
}

View Slide

public class Timeline { 
private final List cache = new ArrayList<>(); 
private final TwitterApi api; 
 
public Timeline(TwitterApi api, String user) { 
this.api = api; 
} 
 
public List get() { /* ... */ } 
public void loadMore(int amount) { /* ... */ } 
}

View Slide

 
public Tweeter(String user) { 
} 
 
} 
}

View Slide

private final TwitterApi api; 
 
public Tweeter(TwitterApi api, String user) { 
this.api = api; 
} 
 
} 
}

View Slide

tweeter.tweet("Hello, #Devoxx 2014!"); 
 
Timeline timeline = new Timeline("JakeWharton"); 
}

View Slide

TwitterApi api = new TwitterApi(client); 
String user = "Jake Wharton"; 
 
Tweeter tweeter = new Tweeter(api, user); 
tweeter.tweet("Hello, #Devoxx 2014!"); 
 
Timeline timeline = new Timeline(api, user); 
}

View Slide

Twitter API
Tweeter HTTP Client

View Slide

Twitter API
Tweeter
HTTP Client
Tweeter

View Slide

Twitter API
Tweeter
HTTP Client
Tweeter
• How do we avoid the boilerplate that comes with the pattern?

View Slide

Library Rescue
• Spring
• Guice
• Dagger (v1)
• PicoContainer
• CDI
• Others…

View Slide

Guice Dagger
(v1)

View Slide

Guice

View Slide

Guice
• Developed at Google by Bob Lee, later Jesse Wilson, others.

View Slide

Guice
• Adopted and maintained by Java Core Libraries team.

View Slide

Guice
• Powerful, dynamic, well-tested, wide-spread, etc…

View Slide

Guice
• Conﬁguration problems occur at runtime.

View Slide

Guice
• Conﬁguration problems occur at runtime.
• Slow initialization, slow injection, memory concerns.

View Slide

Dagger (v1)

View Slide

Dagger (v1)
• Developed at Square by Jesse Wilson advised by Bob Lee.

View Slide

Dagger (v1)
• Initially targeted at highly resource constrained environments.

View Slide

Dagger (v1)
• Static analysis of all dependencies and injection points.

View Slide

Dagger (v1)
• Fail as early as possible (compile-time, not runtime)

View Slide

Dagger (v1)
• Fail as early as possible (compile-time, not runtime)
• Eliminate reflection on methods, ﬁelds, and annotations.

View Slide

Dagger (v1)

View Slide

Dagger (v1)
• Wide-spread, successful use in large Android applications.

View Slide

Dagger (v1)
• Triggers over-eager class loading on graph creation.

View Slide

Dagger (v1)
• FQCN string-based keys in map-like data structure.

View Slide

Dagger (v1)
• Lack of full static scope analysis and scope annotations.

View Slide

Dagger (v1)
• Lack of full static scope analysis and scope annotations.
• Still uses reflection to load generated classes.

View Slide

Dagger (v2)

View Slide

Dagger (v2)
• Proposed and implemented by Java Core Libraries team.

View Slide

Dagger (v2)
• Eliminate runtime library and generated code overhead.

View Slide

Dagger (v2)
• Shift remaining runtime analysis to compile time.

View Slide

Dagger (v2)
• Shift remaining runtime analysis to compile time.
• Scoping with annotations and associated static analysis.

View Slide

Dagger API

View Slide

Dagger API
• @Module + @Provides: mechanism for providing dependencies.

View Slide

Dagger API
• @Inject: mechanism for requesting dependencies.

View Slide

Dagger API
• @Component: bridge between modules and injections

View Slide

Dagger API
• @Component: bridge between modules and injections
• Plus some other sugar, magic, and conventions.

View Slide

Providing Dependencies

View Slide

• Modules are classes whose methods provide dependencies.

View Slide

• @Module on the class.

View Slide

• @Provides (and friends) on each method.

View Slide

 
public class NetworkModule { 
 
OkHttpClient provideOkHttpClient() { 
return new OkHttpClient(); 
} 
 
 
TwitterApi provideTwitterApi(OkHttpClient client) { 
return new TwitterApi(client); 
} 
}

View Slide

 
 
} 
 
 
} 
}
@Module

View Slide

 
 
} 
 
 
} 
}
@Module
!
!
@Provides
!
!
!
!
!
!
!
@Provides

View Slide

 
 
} 
 
 
} 
}
@Module
!
!
@Provides
!
!
!
!
!
!
!
@Provides
!
!
@Singleton
!
!
!
!
!
!
!
@Singleton

View Slide


View Slide

NetworkModule#provideOkHttpClient
NetworkModule#provideTwitterApi

View Slide

OkHttpClient
TwitterApi

View Slide

OkHttpClient
TwitterApi
}

View Slide

OkHttpClient
TwitterApi

View Slide


View Slide

!
!
!
• Designed to be partitioned and composed together.

View Slide

 
public class TwitterModule { 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
}

View Slide

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
}
@Module

View Slide

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
}
 
 
 
public TwitterModule(String user) { 
}
@Module

View Slide

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
}
 
 
 
}
 
 
 
 
 
 
 
@Provides @Singleton 
Tweeter provideTweeter(TwitterApi api) { 
return new Tweeter(api, user); 
}
@Module

View Slide

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
}
 
 
 
}
 
 
 
 
 
 
 
}
 
 
 
 
 
 
 
 
 
 
 
 
 
Timeline provideTimeline(TwitterApi api) { 
return new Timeline(api, user); 
}
@Module

View Slide

OkHttpClient
TwitterApi

View Slide

OkHttpClient
TwitterApi
TwitterModule#provideTweeter
TwitterModule#provideTimeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Tweeter

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Tweeter TwitterModule#provideTweeter

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
TwitterApi

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
TwitterApi NetworkModule#provideTwitterApi

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
OkHttpClient

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
OkHttpClient NetworkModule#provideOkHttpClient

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
OkHttpClient

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
OkHttpClient
OkHttpClient

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
OkHttpClient
OkHttpClient
TwitterApi

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
TwitterApi
OkHttpClient
OkHttpClient
TwitterApi

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Tweeter
TwitterApi
OkHttpClient
OkHttpClient
TwitterApi
Tweeter

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Timeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Timeline TwitterModule#provideTimeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Timeline

View Slide

OkHttpClient
TwitterApi
Tweeter
Timeline
Timeline
Timeline

View Slide

Requesting Dependencies

View Slide

• @Inject annotation required.

View Slide

• @Inject annotation required.
• Constructor, ﬁeld, and method injection.

View Slide

Constructor Injection

View Slide

• @Inject on a single constructor.

View Slide

• Constructor parameters are dependencies.

View Slide

• Dependencies can be stored in private and ﬁnal ﬁelds.

View Slide

public class TwitterApplication { 
private final Tweeter tweeter; 
private final Timeline timeline; 
 
@Inject 
public TwitterApplication(Tweeter tweeter, Timeline timeline) { 
this.tweeter = tweeter; 
this.timeline = timeline; 
} 
 
// ... 
}

View Slide


View Slide

• Implicitly made available for downstream injection.

View Slide

@Module 
} 
 
} 
}

View Slide

@Module 
} 
 
} 
}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
} 
}

View Slide

 
 
 
} 
 
Request request = // TODO build POST request ... 
} 
}

View Slide

 
 
 
} 
 
} 
}
 
 
 
@Inject

View Slide

 
 
 
} 
 
} 
}
 
 
 
@Inject
@Singleton

View Slide

Method Injection

View Slide

Method Injection
• @Inject on methods.

View Slide

Method Injection
• Method parameters are dependencies.

View Slide

Method Injection
• Injection happens after object is fully instantiated.

View Slide

Method Injection
• Injection happens after object is fully instantiated.
• Only one valid use case: passing ‘this’ to a dependency.

View Slide

 
@Inject 
} 
 
 
 
 
}

View Slide

 
@Inject 
} 
 
 
 
 
}
 
@Inject 
} 
 
 
 
 
}
!
!
!
!
!
!
!
!
!
!
@Inject 
public void enableStreaming(Streaming streaming) { 
streaming.register(this); 
}

View Slide

 
@Inject 
} 
 
 
 
 
}
!
!
!
!
!
!
!
!
!
!
@Inject 
public void enableStreaming(Streaming streaming) { 
streaming.register(this); 
}

View Slide

Field Injection

View Slide

Field Injection
• @Inject on ﬁelds for dependencies.

View Slide

Field Injection
• Field may not be private or ﬁnal.

View Slide

@Inject Tweeter tweeter; 
@Inject Timeline timeline; 
 
// ... 
}

View Slide

public class TwitterActivity extends Activity { 
 
// ... 
}

View Slide

public class TwitterProcessor extends AbstractProcessor { 
 
// ... 
}

View Slide

Field Injection

View Slide

Field Injection
• Injection happens after the object is fully instantiated.

View Slide

Field Injection
• Injection happens after the object is fully instantiated.
• Object is usually responsible for or aware of injection.

View Slide

Components

View Slide

Components
• Bridge between modules and injection.

View Slide

Components
• The injector.

View Slide

@Component
!
public interface TwitterComponent {
 
 
}

View Slide

@Component
!
 
 
}
(modules = {
NetworkModule.class, 
TwitterModule.class, 
})

View Slide

@Component
!
 
 
}
(modules = {
})
@Singleton

View Slide

@Component
 
 
 
 
 
Tweeter tweeter(); 
Timeline timeline();
!
 
 
}
(modules = {
})
@Singleton

View Slide

TwitterComponent component = Dagger_TwitterComponent.builder() 
.networkModule(new NetworkModule()) 
.twitterModule(new TwitterModule("JakeWharton")) 
.build();

View Slide

.networkModule(new NetworkModule()) 
.build();
!
!
!
!
!
!
Timeline timeline = component.timeline();
!
!
!
!
 
Tweeter tweeter = component.tweeter();

View Slide

TwitterComponent component = Dagger_TwitterComponent.builder()
 
 
.build();
!
 
.networkModule(new NetworkModule())
 
.networkModule(new NetworkModule())
 
 
 
!
!

View Slide

 
 
.build();
!
 
 
 
!
!

View Slide

 
 
.build();
!
}
 
 
 
!
!

View Slide

public class TwitterApplication implements Runnable { 
 
@Inject 
} 
 
@Override public void run() { 
tweeter.tweet("Hello #Devoxx 2014!"); 
 
} 
} 
}

View Slide

@Singleton
@Component(modules = { 
}) 
interface TwitterComponent { 
TwitterApplication app(); 
}

View Slide

@Singleton
}) 
}
.build(); 
component.app().run();

View Slide

public class TwitterApplication implements Runnable { 
 
@Override public void run() { 
tweeter.tweet("Hello #Devoxx 2014!"); 
 
} 
}
}

View Slide

@Singleton
}) 
void injectApp(TwitterApplication app);
}

View Slide

@Singleton
}) 
}
.build();

View Slide

@Singleton
}) 
}
.build();
TwitterApplication app = new TwitterApplication(); 
component.injectApp(app); 
app.run();

View Slide

@Singleton
}) 
void injectActivity(TwitterActivity activity);
}
.build();
TwitterActivity activity = // Android creates instance... 
component.injectActivity(activity);
@Singleton
}) 
}
.build();

View Slide

@Singleton
}) 
}
.build();
TwitterActivity activity = // Android creates instance... 
component.injectActivity(activity);

View Slide

@Singleton
}) 
void injectProcessor(TwitterProcessor processor);
}
.build();
TwitterProcessor processor = // ServiceLoader creates instance... 
component.injectProcessor(processor);
@Singleton
}) 
}
.build();

View Slide

@Singleton
}) 
}
.build();
TwitterProcessor processor = // ServiceLoader creates instance... 
component.injectProcessor(processor);

View Slide

@Singleton
}) 
TwitterApplication injectApp(TwitterApplication app);
}
.build();
component.injectApp(app).run();
@Singleton
}) 
}
.build();

View Slide

@Singleton
}) 
}
.build();
component.injectApp(app).run();

View Slide

Components
• The injector.

View Slide

Components
• The injector.
• Implementation of scopes.

View Slide

@Singleton 
@Component(modules = NetworkModule.class) 
public interface ApiComponent {
 
 
 
}

View Slide

@Singleton 
 
 
 
}
@Component(
 
modules = TwitterModule.class 
) 
public interface TwitterComponent { 
}

View Slide

@Singleton 
 
 
 
}
@Component(
 
dependencies = ApiComponent.class,
 
) 
}

View Slide

@Singleton 
 
 
 
}
 
 
 
TwitterApi api(); 
@Component(
 
 
) 
}

View Slide

@Singleton 
TwitterApi api();
}
@Component( 
) 
}
@Singleton

View Slide

@Singleton 
TwitterApi api();
}
@Component( 
) 
}

View Slide

@Module 
 
} 
 
} 
 
} 
}

View Slide

@Module 
 
} 
 
@Provides 
} 
 
@Provides 
} 
}

View Slide

ApiComponent apiComponent = Dagger_ApiComponent. builder().build();

View Slide

ApiComponent apiComponent = Dagger_ApiComponent. create();
ApiComponent apiComponent = Dagger_ApiComponent.

View Slide


View Slide

TwitterComponent twitterComponent = Dagger_TwitterComponent.builder() 
.apiComponent(apiComponent) 
.twitterModule(new TwitterModule("Jake Wharton")) 
.build();

View Slide

TwitterComponent twitterComponent = Dagger_TwitterComponent.builder() 
.apiComponent(apiComponent) 
.twitterModule(new TwitterModule("Jake Wharton")) 
.build();
component.app().run();

View Slide

Scope Annotations

View Slide

Scope Annotations
• Only create a single instance.

View Slide

Scope Annotations
• @Singleton is the “largest” scope.

View Slide

Scope Annotations
• Custom annotations for semantic clarity, shorter lifetime.

View Slide

public @interface User { 
}
Scope Annotations

View Slide

public @interface User { 
}
@Scope
Scope Annotations

View Slide

@Module 
 
} 
 
@Provides 
} 
 
@Provides 
} 
}

View Slide

@Module 
 
} 
 
@Provides 
} 
 
@Provides 
} 
}
@Module 
 
} 
 
@Provides @User 
} 
 
@Provides @User 
} 
}

View Slide

@Component( 
) 
}

View Slide

@Component( 
) 
}
@User

View Slide

OkHttpClient
TwitterApi
NetworkModule

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent
TwitterApi

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent
TwitterApi Tweeter
Timeline
TwitterModule

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent
TwitterApi Tweeter
Timeline
TwitterModule
TwitterComponent

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent
TwitterApi Tweeter
Timeline
TwitterModule
TwitterComponent
TwitterApp

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent
TwitterApi

View Slide

OkHttpClient
TwitterApi
NetworkModule
ApiComponent
TwitterApi Tweeter
Timeline
TwitterModule
TwitterComponent
TwitterApp

View Slide

Under The Hood

View Slide

Under The Hood
OkHttpClient
TwitterApi
Tweeter
Timeline

View Slide

@Module 
} 
 
} 
}

View Slide

OkHttpClient provideOkHttpClient() {}
TwitterApi provideTwitterApi(OkHttpClient) {} 
}
public final class NetworkModule_ProvideOkHttpClientFactory
implements Factory {
 
private final NetworkModule module; 
 
public NetworkModule_ProvideOkHttpClientFactory(NetworkModule module) {  
this.module = module; 
} 
 
@Override 
public OkHttpClient get() {  
return module.provideOkHttpClient(); 
} 
}

View Slide

}
public final class NetworkModule_ProvideOkHttpClientFactory
 
 
public NetworkModule_ProvideOkHttpClientFactory(NetworkModule module) { 
} 
 
@Override 
} 
}

View Slide

}
public final class NetworkModule_ProvideOkHttpClientFactory { 
} 
}
public final class NetworkModule_ProvideTwitterApiFactory
 
private final Provider clientProvider; 
 
public NetworkModule_ProvideTwitterApiFactory(
NetworkModule module, Provider clientProvider) { 
this.clientProvider = clientProvider; 
} 
 
@Override 
public TwitterApi get() { 
return module.provideTwitterApi(clientProvider.get()); 
} 
}

View Slide

@Singleton 
interface ApiComponent { 
}

View Slide

}
public final class Dagger_ApiComponent implements ApiComponent { 
// ...
 
public static final class Builder { 
private NetworkModule networkModule; 
 
public ApiComponent build() { 
if (networkModule == null) networkModule = new NetworkModule(); 
return new Dagger_ApiComponent(this); 
} 
 
public Builder networkModule(NetworkModule networkModule) { 
if (networkModule == null) throw new NullPointerException(); 
this.networkModule = networkModule; 
return this; 
} 
} 
}

View Slide

}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
}

View Slide

}
private Provider provideOkHttpClientProvider; 
private Provider provideTwitterApiProvider; 
 
private Dagger_ApiComponent(Builder builder) { 
NetworkModule networkModule = builder.networkModule; 
provideOkHttpClientProvider = ScopedProvider.create(
new NetworkModule_ProvideOkHttpClientFactory(networkModule)); 
provideTwitterApiProvider = ScopedProvider.create(
new NetworkModule_ProvideTwitterApiFactory(networkModule,
provideOkHttpClientProvider)); 
} 
 
@Override 
public TwitterApi api() { 
return provideTwitterApiProvider.get(); 
}

View Slide

@Module 
 
} 
 
@Provides 
} 
 
@Provides 
} 
}
@Component( 
dependencies = ApiComponent.class, 
) 
}

View Slide

public final class TwitterModule_ProvideTweeterFactory
 
private final TwitterModule module; 
private final Provider apiProvider; 
 
public TwitterModule_ProvideTweeterFactory(
TwitterModule module, Provider apiProvider) { 
this.apiProvider = apiProvider; 
} 
 
@Override 
public Tweeter get() { 
return module.provideTweeter(apiProvider.get()); 
} 
}

View Slide

public final class TwitterModule_ProvideTimelineFactory
 
private final TwitterModule module; 
private final Provider apiProvider; 
 
public TwitterModule_ProvideTimelineFactory(
TwitterModule module, Provider apiProvider) { 
this.apiProvider = apiProvider; 
} 
 
@Override 
public Timeline get() { 
return module.provideTimeline(apiProvider.get()); 
} 
}

View Slide

public final class TwitterApplication_Factory
 
private final Provider tweeterProvider; 
private final Provider timelineProvider; 
 
public TwitterApplication_Factory(
Provider tweeterProvider,
Provider timelineProvider) { 
this.tweeterProvider = tweeterProvider; 
this.timelineProvider = timelineProvider; 
} 
 
@Override 
public TwitterApplication get() { 
return new TwitterApplication(tweeterProvider.get(),
timelineProvider.get()); 
} 
}

View Slide

public static final class Builder { 
private TwitterModule twitterModule; 
private ApiComponent apiComponent; 
 
public TwitterComponent build() { 
if (twitterModule == null) throw new IllegalStateException("..."); 
if (apiComponent == null) throw new IllegalStateException("..."); 
return new Dagger_TwitterComponent(this); 
} 
 
public Builder twitterModule(TwitterModule twitterModule) { 
if (twitterModule == null) throw new NullPointerException("twitterModule"); 
this.twitterModule = twitterModule; 
return this; 
} 
 
public Builder apiComponent(ApiComponent apiComponent) { 
if (apiComponent == null) throw new NullPointerException("apiComponent"); 
this.apiComponent = apiComponent; 
return this; 
} 
}

View Slide

public final class Dagger_TwitterComponent implements TwitterComponent { 
// ... 
 
private Dagger_TwitterComponent(Builder builder) { 
twitterModule = builder.twitterModule; 
apiComponent = builder.apiComponent; 
 
apiProvider = new Factory() { 
@Override public TwitterApi get() { 
return apiComponent.api(); 
} 
}; 
 
provideTweeterProvider =
new TwitterModule_ProvideTweeterFactory(twitterModule, apiProvider); 
provideTimelineProvider =
new TwitterModule_ProvideTimelineFactory(twitterModule, apiProvider); 
twitterApplicationProvider = new TwitterApplication_Factory(
provideTweeterProvider, provideTimelineProvider); 
}

View Slide

Dagger_ApiComponent.create()

View Slide

new NetworkModule

View Slide

new NetworkModule
new NetworkModule_ProvideOkHttpClientFactory
new NetworkModule_ProvideTwitterApiFactory

View Slide

new NetworkModule
new TwitterModule("Jake Wharton")

View Slide

new NetworkModule
Dagger_TwitterComponent.builder()...build()

View Slide

new NetworkModule
new Factory

View Slide

new NetworkModule
new TwitterModule_ProvideTweeterFactory
new TwitterModule_ProvideTimelineFactory
new TwitterApplication_Factory
new Factory

View Slide

twitterComponent.app()

View Slide

twitterApplicationProvider.get()

View Slide

tweeterProvider.get()
apiProvider.get()
apiComponent.api()

View Slide

apiProvider.get()
provideTwitterApiProvider.get()
networkModule.provideOkHttpClient()
apiComponent.api()
clientProvider.get()

View Slide

apiProvider.get()
apiComponent.api()
new OkHttpClient()

View Slide

apiProvider.get()
networkModule.provideTwitterApi(..)
apiComponent.api()
new OkHttpClient()

View Slide

apiProvider.get()
apiComponent.api()
new OkHttpClient()
new TwitterApi(..)

View Slide

apiProvider.get()
twitterModule.provideTweeter(..)
apiComponent.api()
new OkHttpClient()
new TwitterApi(..)

View Slide

apiProvider.get()
apiComponent.api()
new OkHttpClient()
new TwitterApi(..)
new Tweeter(..)

View Slide

apiProvider.get()
timelineProvider.get()
apiProvider.get()
apiComponent.api()
apiComponent.api()
new OkHttpClient()
new TwitterApi(..)
new Tweeter(..)

View Slide

apiProvider.get()
apiProvider.get()
apiComponent.api()
apiComponent.api()
new OkHttpClient()
new TwitterApi(..)
new Tweeter(..)

View Slide

apiProvider.get()
apiProvider.get()
apiComponent.api()
apiComponent.api()
twitterModule.provideTimeline(..)
new OkHttpClient()
new TwitterApi(..)
new Tweeter(..)

View Slide

apiProvider.get()
apiProvider.get()
apiComponent.api()
apiComponent.api()
new OkHttpClient()
new TwitterApi(..)
new Tweeter(..)
new Timeline(..)

View Slide

apiProvider.get()
apiProvider.get()
apiComponent.api()
apiComponent.api()
new TwitterApplication(..)
new OkHttpClient()
new TwitterApi(..)
new Tweeter(..)
new Timeline(..)

View Slide

Annotation Processing

View Slide

Annotation Processing
bit.ly/apt-bd

View Slide

JSR 330

View Slide

public @interface Inject {}
public @interface Qualifier {}
public @interface Named { 
String value(); 
}
public interface Provider { 
T get(); 
}
public @interface Scope {}
JSR 330
public @interface Singleton {}

View Slide

Dagger 1

View Slide

public abstract class ObjectGraph { 
public static ObjectGraph create(Object... modules) {} 
public abstract ObjectGraph plus(Object... modules); 
public abstract void validate(); 
public abstract void injectStatics(); 
public abstract T get(Class type); 
public abstract T inject(T instance); 
}
public interface Lazy { 
T get(); 
}
public @interface Module { 
Class>[] injects() default { }; 
Class>[] staticInjections() default { }; 
Class>[] includes() default { }; 
Class> addsTo() default Void.class; 
boolean overrides() default false; 
boolean complete() default true; 
boolean library() default true; 
}
public @interface Provides { 
enum Type { UNIQUE, SET } 
Type type() default Type.UNIQUE; 
}
public interface MembersInjector { 
void injectMembers(T instance); 
}
Dagger 1

View Slide

}
T get(); 
}
}
enum Type { UNIQUE, SET } 
Type type() default Type.UNIQUE; 
}
}
Dagger 1
T get(); 
}
}
}
}

View Slide

Dagger 2

View Slide

public @interface Component { 
Class>[] modules() default {}; 
Class>[] dependencies() default {}; 
}
T get(); 
}
}
}
public @interface MapKey { 
boolean unwrapValue(); 
}
Dagger 2

View Slide

public @interface Component { 
Class>[] modules() default {}; 
Class>[] dependencies() default {}; 
}
T get(); 
}
}
}
}
Dagger 2
T get(); 
}
}

View Slide

Dependency Injection with Dagger 2 (Devoxx 2014)

Dependency Injection with Dagger 2 (Devoxx 2014)

Jake Wharton
PRO

More Decks by Jake Wharton

Other Decks in Technology

Featured

Transcript

Dependency Injection with Dagger 2 (Devoxx 2014)

Dependency Injection with Dagger 2 (Devoxx 2014)

Jake Wharton PRO

More Decks by Jake Wharton

Other Decks in Technology

Featured

Transcript

Jake Wharton
PRO