Tweet
Tweet

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dependency injection with Dagger 2 Jake Wharton

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Dependency Injection flickr.com/photos/sunsetnoir/6984108500

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

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Dependency Injection • First and foremost a pattern

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Dependency Injection • First and foremost a pattern • Every single app has some form of dependency injection

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Dependency Injection • First and foremost a pattern • Every single app has some form of dependency injection Tweeter

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Dependency Injection • First and foremost a pattern • Every single app has some form of dependency injection Twitter API Tweeter

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Dependency Injection • First and foremost a pattern • Every single app has some form of dependency injection Twitter API Tweeter HTTP Client

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

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

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public class Tweeter {
 public void tweet(String tweet) {
 TwitterApi api = new TwitterApi();
 api.postTweet("JakeWharton", tweet);
 }
 } public class TwitterApi {
 public void postTweet(String user, String tweet) {
 OkHttpClient client = new OkHttpClient();
 Request request = // TODO build POST request...
 client.newCall(request).execute();
 }
 } Tweeter tweeter = new Tweeter();
 tweeter.tweet("Hello, #Devoxx 2014!");

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

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

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

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

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

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

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

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

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

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

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public class Tweeter {
 private final TwitterApi api = new TwitterApi(new OkHttpClient());
 private final String user;
 
 public Tweeter(String user) {
 this.user = user;
 }
 
 public void tweet(String tweet) {
 api.postTweet(user, tweet);
 }
 }

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public class Tweeter {
 private final TwitterApi api = new TwitterApi(new OkHttpClient());
 private final String user;
 
 public Tweeter(String user) {
 this.user = user;
 }
 
 public void tweet(String tweet) {
 api.postTweet(user, tweet);
 }
 }

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

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

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

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

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

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

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

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

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public class Tweeter {
 private final TwitterApi api = new TwitterApi(new OkHttpClient());
 private final String user;
 
 public Tweeter(String user) {
 this.user = user;
 }
 
 public void tweet(String tweet) {
 api.postTweet(user, tweet);
 }
 }

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

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

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Tweeter tweeter = new Tweeter("JakeWharton");
 tweeter.tweet("Hello, #Devoxx 2014!");
 
 Timeline timeline = new Timeline("JakeWharton");
 timeline.loadMore(20);
 for (Tweet tweet : timeline.get()) {
 System.out.println(tweet);
 }

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OkHttpClient client = new OkHttpClient();
 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);
 timeline.loadMore(20);
 for (Tweet tweet : timeline.get()) {
 System.out.println(tweet);
 }

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OkHttpClient client = new OkHttpClient();
 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);
 timeline.loadMore(20);
 for (Tweet tweet : timeline.get()) {
 System.out.println(tweet);
 }

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Dependency Injection • First and foremost a pattern • Every single app has some form of dependency injection Twitter API Tweeter HTTP Client

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Dependency Injection • First and foremost a pattern • Every single app has some form of dependency injection Twitter API Tweeter HTTP Client Tweeter

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

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

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Guice Dagger (v1)

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Guice

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

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Guice • Developed at Google by Bob Lee, later Jesse Wilson, others. • Adopted and maintained by Java Core Libraries team.

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Guice • Developed at Google by Bob Lee, later Jesse Wilson, others. • Adopted and maintained by Java Core Libraries team. • Powerful, dynamic, well-tested, wide-spread, etc…

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Guice • Developed at Google by Bob Lee, later Jesse Wilson, others. • Adopted and maintained by Java Core Libraries team. • Powerful, dynamic, well-tested, wide-spread, etc… • Configuration problems occur at runtime.

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Guice • Developed at Google by Bob Lee, later Jesse Wilson, others. • Adopted and maintained by Java Core Libraries team. • Powerful, dynamic, well-tested, wide-spread, etc… • Configuration problems occur at runtime. • Slow initialization, slow injection, memory concerns.

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Dagger (v1)

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

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Dagger (v1) • Developed at Square by Jesse Wilson advised by Bob Lee. • Initially targeted at highly resource constrained environments.

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Dagger (v1) • Developed at Square by Jesse Wilson advised by Bob Lee. • Initially targeted at highly resource constrained environments. • Static analysis of all dependencies and injection points.

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Dagger (v1) • Developed at Square by Jesse Wilson advised by Bob Lee. • Initially targeted at highly resource constrained environments. • Static analysis of all dependencies and injection points. • Fail as early as possible (compile-time, not runtime)

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Dagger (v1) • Developed at Square by Jesse Wilson advised by Bob Lee. • Initially targeted at highly resource constrained environments. • Static analysis of all dependencies and injection points. • Fail as early as possible (compile-time, not runtime) • Eliminate reflection on methods, fields, and annotations.

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Dagger (v1)

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

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Dagger (v1) • Wide-spread, successful use in large Android applications. • Triggers over-eager class loading on graph creation.

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Dagger (v1) • Wide-spread, successful use in large Android applications. • Triggers over-eager class loading on graph creation. • FQCN string-based keys in map-like data structure.

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Dagger (v1) • Wide-spread, successful use in large Android applications. • Triggers over-eager class loading on graph creation. • FQCN string-based keys in map-like data structure. • Lack of full static scope analysis and scope annotations.

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Dagger (v1) • Wide-spread, successful use in large Android applications. • Triggers over-eager class loading on graph creation. • FQCN string-based keys in map-like data structure. • Lack of full static scope analysis and scope annotations. • Still uses reflection to load generated classes.

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Dagger (v2)

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

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Dagger (v2) • Proposed and implemented by Java Core Libraries team. • Eliminate runtime library and generated code overhead.

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Dagger (v2) • Proposed and implemented by Java Core Libraries team. • Eliminate runtime library and generated code overhead. • Shift remaining runtime analysis to compile time.

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Dagger (v2) • Proposed and implemented by Java Core Libraries team. • Eliminate runtime library and generated code overhead. • Shift remaining runtime analysis to compile time. • Scoping with annotations and associated static analysis.

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Dagger API

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

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

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Dagger API • @Module + @Provides: mechanism for providing dependencies. • @Inject: mechanism for requesting dependencies. • @Component: bridge between modules and injections

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Dagger API • @Module + @Provides: mechanism for providing dependencies. • @Inject: mechanism for requesting dependencies. • @Component: bridge between modules and injections • Plus some other sugar, magic, and conventions.

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Providing Dependencies

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Providing Dependencies • Modules are classes whose methods provide dependencies.

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Providing Dependencies • Modules are classes whose methods provide dependencies. • @Module on the class.

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Providing Dependencies • Modules are classes whose methods provide dependencies. • @Module on the class. • @Provides (and friends) on each method.

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

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

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 public class NetworkModule {
 
 OkHttpClient provideOkHttpClient() {
 return new OkHttpClient();
 }
 
 
 TwitterApi provideTwitterApi(OkHttpClient client) {
 return new TwitterApi(client);
 }
 } @Module ! ! @Provides ! ! ! ! ! ! ! @Provides

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 public class NetworkModule {
 
 OkHttpClient provideOkHttpClient() {
 return new OkHttpClient();
 }
 
 
 TwitterApi provideTwitterApi(OkHttpClient client) {
 return new TwitterApi(client);
 }
 } @Module ! ! @Provides ! ! ! ! ! ! ! @Provides ! ! @Singleton ! ! ! ! ! ! ! @Singleton

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Providing Dependencies

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Providing Dependencies NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterApi provideTwitterApi(OkHttpClient client) {
 return new TwitterApi(client);
 }

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies • Modules are classes whose methods provide dependencies. • @Module on the class. • @Provides (and friends) on each method.

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Providing Dependencies • Modules are classes whose methods provide dependencies. • @Module on the class. • @Provides (and friends) on each method. ! ! ! • Designed to be partitioned and composed together.

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 public class TwitterModule {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 }

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 public class TwitterModule {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 } @Module

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 public class TwitterModule {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 } 
 
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 } @Module

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 public class TwitterModule {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 } 
 
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 } 
 public class TwitterModule {
 
 
 
 
 
 
 @Provides @Singleton
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 } @Module

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 public class TwitterModule {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 } 
 
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 } 
 public class TwitterModule {
 
 
 
 
 
 
 @Provides @Singleton
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 } 
 
 
 
 
 
 
 
 
 
 
 
 
 @Provides @Singleton
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 } @Module

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient NetworkModule#provideOkHttpClient

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient NetworkModule#provideOkHttpClient NetworkModule#provideOkHttpClient

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient NetworkModule#provideOkHttpClient OkHttpClient

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient OkHttpClient

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient OkHttpClient NetworkModule#provideTwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi NetworkModule#provideTwitterApi OkHttpClient OkHttpClient NetworkModule#provideTwitterApi TwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi OkHttpClient OkHttpClient TwitterApi

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterModule#provideTweeter TwitterApi OkHttpClient OkHttpClient TwitterApi TwitterModule#provideTweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterApi OkHttpClient OkHttpClient TwitterApi TwitterModule#provideTweeter Tweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterApi OkHttpClient OkHttpClient TwitterApi Tweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterApi OkHttpClient OkHttpClient TwitterApi Tweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Tweeter TwitterApi OkHttpClient OkHttpClient TwitterApi Tweeter

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline TwitterModule#provideTimeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline TwitterModule#provideTimeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline TwitterModule#provideTimeline TwitterModule#provideTimeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline TwitterModule#provideTimeline Timeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline Timeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline Timeline

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Providing Dependencies OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline Timeline Timeline

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Requesting Dependencies

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Requesting Dependencies • @Inject annotation required.

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

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Constructor Injection

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Constructor Injection • @Inject on a single constructor.

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Constructor Injection • @Inject on a single constructor. • Constructor parameters are dependencies.

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Constructor Injection • @Inject on a single constructor. • Constructor parameters are dependencies. • Dependencies can be stored in private and final fields.

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

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Constructor Injection • @Inject on a single constructor. • Constructor parameters are dependencies. • Dependencies can be stored in private and final fields.

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Constructor Injection • @Inject on a single constructor. • Constructor parameters are dependencies. • Dependencies can be stored in private and final fields. • Implicitly made available for downstream injection.

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@Module
 public class NetworkModule {
 @Provides @Singleton
 OkHttpClient provideOkHttpClient() {
 return new OkHttpClient();
 }
 
 @Provides @Singleton
 TwitterApi provideTwitterApi(OkHttpClient client) {
 return new TwitterApi(client);
 }
 }

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@Module
 public class NetworkModule {
 @Provides @Singleton
 OkHttpClient provideOkHttpClient() {
 return new OkHttpClient();
 }
 
 @Provides @Singleton
 TwitterApi provideTwitterApi(OkHttpClient client) {
 return new TwitterApi(client);
 }
 } 
 
 
 
 
 
 
 @Provides @Singleton
 
 
 
 
 
 
 
 
 
 
 
 TwitterApi provideTwitterApi(OkHttpClient client) {
 
 
 
 
 
 
 
 
 
 
 
 return new TwitterApi(client);
 
 
 
 
 
 
 
 
 
 
 
 }
 }

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

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

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public class TwitterApi {
 private final OkHttpClient client;
 
 
 
 public TwitterApi(OkHttpClient client) {
 this.client = client;
 }
 
 public void postTweet(String user, String tweet) {
 Request request = // TODO build POST request ...
 client.newCall(request).execute();
 }
 } 
 
 
 @Inject @Singleton

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Method Injection

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Method Injection • @Inject on methods.

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Method Injection • @Inject on methods. • Method parameters are dependencies.

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Method Injection • @Inject on methods. • Method parameters are dependencies. • Injection happens after object is fully instantiated.

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Method Injection • @Inject on methods. • Method parameters are dependencies. • Injection happens after object is fully instantiated. • Only one valid use case: passing ‘this’ to a dependency.

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

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public class TwitterApplication {
 private final Tweeter tweeter;
 private final Timeline timeline;
 
 @Inject
 public TwitterApplication(Tweeter tweeter, Timeline timeline) {
 this.tweeter = tweeter;
 this.timeline = timeline;
 }
 
 
 
 
 } public class TwitterApplication {
 private final Tweeter tweeter;
 private final Timeline timeline;
 
 @Inject
 public TwitterApplication(Tweeter tweeter, Timeline timeline) {
 this.tweeter = tweeter;
 this.timeline = timeline;
 }
 
 
 
 
 } ! ! ! ! ! ! ! ! ! ! @Inject
 public void enableStreaming(Streaming streaming) {
 streaming.register(this);
 }

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public class TwitterApplication {
 private final Tweeter tweeter;
 private final Timeline timeline;
 
 @Inject
 public TwitterApplication(Tweeter tweeter, Timeline timeline) {
 this.tweeter = tweeter;
 this.timeline = timeline;
 }
 
 
 
 
 } ! ! ! ! ! ! ! ! ! ! @Inject
 public void enableStreaming(Streaming streaming) {
 streaming.register(this);
 }

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Field Injection

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Field Injection • @Inject on fields for dependencies.

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Field Injection • @Inject on fields for dependencies. • Field may not be private or final.

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public class TwitterApplication {
 @Inject Tweeter tweeter;
 @Inject Timeline timeline;
 
 // ...
 }

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public class TwitterActivity extends Activity {
 @Inject Tweeter tweeter;
 @Inject Timeline timeline;
 
 // ...
 }

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public class TwitterProcessor extends AbstractProcessor {
 @Inject Tweeter tweeter;
 @Inject Timeline timeline;
 
 // ...
 }

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Field Injection • @Inject on fields for dependencies. • Field may not be private or final.

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Field Injection • @Inject on fields for dependencies. • Field may not be private or final. • Injection happens after the object is fully instantiated.

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Field Injection • @Inject on fields for dependencies. • Field may not be private or final. • Injection happens after the object is fully instantiated. • Object is usually responsible for or aware of injection.

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Components

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Components • Bridge between modules and injection.

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Components • Bridge between modules and injection. • The injector.

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@Component ! public interface TwitterComponent { 
 
 }

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

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

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@Component 
 
 
 
 
 Tweeter tweeter();
 Timeline timeline(); ! public interface TwitterComponent { 
 
 } (modules = { NetworkModule.class,
 TwitterModule.class,
 }) @Singleton

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

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TwitterComponent component = Dagger_TwitterComponent.builder()
 .networkModule(new NetworkModule())
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); ! ! ! ! ! ! Timeline timeline = component.timeline(); ! ! ! ! 
 Tweeter tweeter = component.tweeter();

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TwitterComponent component = Dagger_TwitterComponent.builder() 
 
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); ! Tweeter tweeter = component.tweeter(); 
 .networkModule(new NetworkModule()) 
 .networkModule(new NetworkModule()) 
 
 
 ! ! Timeline timeline = component.timeline();

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TwitterComponent component = Dagger_TwitterComponent.builder() 
 
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); ! Tweeter tweeter = component.tweeter(); 
 
 
 ! ! Timeline timeline = component.timeline();

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TwitterComponent component = Dagger_TwitterComponent.builder() 
 
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); ! Tweeter tweeter = component.tweeter(); tweeter.tweet("Hello, #Devoxx 2014!"); timeline.loadMore(20);
 for (Tweet tweet : timeline.get()) {
 System.out.println(tweet);
 } 
 
 
 ! ! Timeline timeline = component.timeline();

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public class TwitterApplication implements Runnable {
 private final Tweeter tweeter;
 private final Timeline timeline;
 
 @Inject
 public TwitterApplication(Tweeter tweeter, Timeline timeline) {
 this.tweeter = tweeter;
 this.timeline = timeline;
 }
 
 @Override public void run() {
 tweeter.tweet("Hello #Devoxx 2014!");
 
 timeline.loadMore(20);
 for (Tweet tweet : timeline.get()) {
 System.out.println(tweet);
 }
 }
 }

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 TwitterApplication app();
 }

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 TwitterApplication app();
 } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build();
 component.app().run();

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public class TwitterApplication implements Runnable {
 @Inject Tweeter tweeter;
 @Inject Timeline timeline;
 
 @Override public void run() {
 tweeter.tweet("Hello #Devoxx 2014!");
 
 timeline.loadMore(20);
 for (Tweet tweet : timeline.get()) {
 System.out.println(tweet);
 }
 } }

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectApp(TwitterApplication app); }

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectApp(TwitterApplication app); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build();

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectApp(TwitterApplication app); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterApplication app = new TwitterApplication();
 component.injectApp(app);
 app.run();

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectActivity(TwitterActivity activity); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterActivity activity = // Android creates instance...
 component.injectActivity(activity); @Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectActivity(TwitterActivity activity); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build();

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectActivity(TwitterActivity activity); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterActivity activity = // Android creates instance...
 component.injectActivity(activity);

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectProcessor(TwitterProcessor processor); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterProcessor processor = // ServiceLoader creates instance...
 component.injectProcessor(processor); @Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectProcessor(TwitterProcessor processor); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build();

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 void injectProcessor(TwitterProcessor processor); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterProcessor processor = // ServiceLoader creates instance...
 component.injectProcessor(processor);

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 TwitterApplication injectApp(TwitterApplication app); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterApplication app = new TwitterApplication();
 component.injectApp(app).run(); @Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 TwitterApplication injectApp(TwitterApplication app); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build();

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@Singleton @Component(modules = {
 NetworkModule.class,
 TwitterModule.class,
 })
 interface TwitterComponent {
 TwitterApplication injectApp(TwitterApplication app); } TwitterComponent component = Dagger_TwitterComponent.builder()
 .twitterModule(new TwitterModule("JakeWharton"))
 .build(); TwitterApplication app = new TwitterApplication();
 component.injectApp(app).run();

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Components • Bridge between modules and injection. • The injector.

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Components • Bridge between modules and injection. • The injector. • Implementation of scopes.

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

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@Singleton
 @Component(modules = NetworkModule.class)
 public interface ApiComponent { 
 
 
 } @Component( 
 modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 }

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@Singleton
 @Component(modules = NetworkModule.class)
 public interface ApiComponent { 
 
 
 } @Component( 
 dependencies = ApiComponent.class, 
 modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 }

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@Singleton
 @Component(modules = NetworkModule.class)
 public interface ApiComponent { 
 
 
 } 
 
 
 TwitterApi api();
 @Component( 
 dependencies = ApiComponent.class, 
 modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 }

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@Singleton
 @Component(modules = NetworkModule.class)
 public interface ApiComponent { TwitterApi api(); } @Component(
 dependencies = ApiComponent.class, modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 } @Singleton

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@Singleton
 @Component(modules = NetworkModule.class)
 public interface ApiComponent { TwitterApi api(); } @Component(
 dependencies = ApiComponent.class, modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 } @Singleton

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@Singleton
 @Component(modules = NetworkModule.class)
 public interface ApiComponent { TwitterApi api(); } @Component(
 dependencies = ApiComponent.class, modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 }

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@Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides @Singleton
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides @Singleton
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 }

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@Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides @Singleton
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides @Singleton
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 }

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@Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 }

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

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

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ApiComponent apiComponent = Dagger_ApiComponent. create();

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

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

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Scope Annotations

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Scope Annotations • Only create a single instance.

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Scope Annotations • Only create a single instance. • @Singleton is the “largest” scope.

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Scope Annotations • Only create a single instance. • @Singleton is the “largest” scope. • Custom annotations for semantic clarity, shorter lifetime.

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public @interface User {
 } Scope Annotations • Only create a single instance. • @Singleton is the “largest” scope. • Custom annotations for semantic clarity, shorter lifetime.

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public @interface User {
 } @Scope Scope Annotations • Only create a single instance. • @Singleton is the “largest” scope. • Custom annotations for semantic clarity, shorter lifetime.

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@Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 }

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@Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 } @Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides @User
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides @User
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 }

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@Component(
 dependencies = ApiComponent.class, modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 }

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@Component(
 dependencies = ApiComponent.class, modules = TwitterModule.class
 )
 public interface TwitterComponent {
 TwitterApplication app();
 } @User

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OkHttpClient TwitterApi NetworkModule

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OkHttpClient TwitterApi NetworkModule ApiComponent

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OkHttpClient TwitterApi NetworkModule ApiComponent

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule TwitterComponent

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule TwitterComponent

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule TwitterComponent TwitterApp

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule TwitterComponent TwitterApp

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule TwitterComponent TwitterApp

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi

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OkHttpClient TwitterApi NetworkModule ApiComponent TwitterApi Tweeter Timeline TwitterModule TwitterComponent TwitterApp

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Under The Hood

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Under The Hood OkHttpClient TwitterApi NetworkModule#provideOkHttpClient NetworkModule#provideTwitterApi TwitterModule#provideTweeter TwitterModule#provideTimeline Tweeter Timeline

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@Module
 public class NetworkModule {
 @Provides @Singleton
 OkHttpClient provideOkHttpClient() {
 return new OkHttpClient();
 }
 
 @Provides @Singleton
 TwitterApi provideTwitterApi(OkHttpClient client) {
 return new TwitterApi(client);
 }
 }

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public class NetworkModule {
 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();
 }
 }

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public class NetworkModule {
 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();
 }
 }

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public class NetworkModule {
 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();
 }
 }

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public class NetworkModule {
 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();
 }
 }

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

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

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

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@Singleton
 @Component(modules = NetworkModule.class)
 interface ApiComponent {
 TwitterApi api();
 }

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interface ApiComponent {
 TwitterApi api();
 } 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;
 }
 }
 }

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interface ApiComponent {
 TwitterApi api();
 } 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;
 }
 }
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 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();
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 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();
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 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();
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 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();
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 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();
 }

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interface ApiComponent {
 TwitterApi api();
 } public final class Dagger_ApiComponent implements ApiComponent {
 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();
 }

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@Module
 public class TwitterModule {
 private final String user;
 
 public TwitterModule(String user) {
 this.user = user;
 }
 
 @Provides
 Tweeter provideTweeter(TwitterApi api) {
 return new Tweeter(api, user);
 }
 
 @Provides
 Timeline provideTimeline(TwitterApi api) {
 return new Timeline(api, user);
 }
 } @Component(
 dependencies = ApiComponent.class,
 modules = TwitterModule.class
 )
 interface TwitterComponent {
 TwitterApplication app();
 }

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

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

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public final class TwitterApplication_Factory implements 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());
 }
 }

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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;
 }
 }

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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;
 }
 }

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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;
 }
 }

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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);
 }

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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);
 }

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Dagger_ApiComponent.create()

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Dagger_ApiComponent.create() new NetworkModule

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Dagger_ApiComponent.create() new NetworkModule new NetworkModule_ProvideOkHttpClientFactory new NetworkModule_ProvideTwitterApiFactory

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Dagger_ApiComponent.create() new NetworkModule new NetworkModule_ProvideOkHttpClientFactory new NetworkModule_ProvideTwitterApiFactory new TwitterModule("Jake Wharton")

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Dagger_ApiComponent.create() new NetworkModule new NetworkModule_ProvideOkHttpClientFactory new NetworkModule_ProvideTwitterApiFactory new TwitterModule("Jake Wharton") Dagger_TwitterComponent.builder()...build()

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Dagger_ApiComponent.create() new NetworkModule new NetworkModule_ProvideOkHttpClientFactory new NetworkModule_ProvideTwitterApiFactory new TwitterModule("Jake Wharton") Dagger_TwitterComponent.builder()...build() new Factory

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Dagger_ApiComponent.create() new NetworkModule new NetworkModule_ProvideOkHttpClientFactory new NetworkModule_ProvideTwitterApiFactory new TwitterModule("Jake Wharton") Dagger_TwitterComponent.builder()...build() new TwitterModule_ProvideTweeterFactory new TwitterModule_ProvideTimelineFactory new TwitterApplication_Factory new Factory

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twitterComponent.app()

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twitterComponent.app() twitterApplicationProvider.get()

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() apiComponent.api()

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() apiComponent.api() clientProvider.get()

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() apiComponent.api() clientProvider.get() new OkHttpClient()

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() new OkHttpClient()

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() new OkHttpClient() new TwitterApi(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() new OkHttpClient() new TwitterApi(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() new OkHttpClient() new TwitterApi(..) new Tweeter(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) timelineProvider.get() apiProvider.get() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() apiComponent.api() new OkHttpClient() new TwitterApi(..) new Tweeter(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) timelineProvider.get() apiProvider.get() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() apiComponent.api() provideTwitterApiProvider.get() new OkHttpClient() new TwitterApi(..) new Tweeter(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) timelineProvider.get() apiProvider.get() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() apiComponent.api() provideTwitterApiProvider.get() twitterModule.provideTimeline(..) new OkHttpClient() new TwitterApi(..) new Tweeter(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) timelineProvider.get() apiProvider.get() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() apiComponent.api() provideTwitterApiProvider.get() twitterModule.provideTimeline(..) new OkHttpClient() new TwitterApi(..) new Tweeter(..) new Timeline(..)

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twitterComponent.app() twitterApplicationProvider.get() tweeterProvider.get() apiProvider.get() provideTwitterApiProvider.get() networkModule.provideOkHttpClient() twitterModule.provideTweeter(..) timelineProvider.get() apiProvider.get() networkModule.provideTwitterApi(..) apiComponent.api() clientProvider.get() apiComponent.api() provideTwitterApiProvider.get() twitterModule.provideTimeline(..) new TwitterApplication(..) new OkHttpClient() new TwitterApi(..) new Tweeter(..) new Timeline(..)

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Annotation Processing

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Annotation Processing bit.ly/apt-bd

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JSR 330

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

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Dagger 1

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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

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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 public interface Lazy {
 T get();
 } public interface MembersInjector {
 void injectMembers(T instance);
 } 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 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);
 }

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Dagger 2

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

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

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More Concepts

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More Concepts • Set and map bindings.

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More Concepts • Set and map bindings. • Asynchronous producers.

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More Concepts • Set and map bindings. • Asynchronous producers. • Testing and module overrides.

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More Concepts • Set and map bindings. • Asynchronous producers. • Testing and module overrides. • AutoFactory for assisted injection.

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github.com/google/dagger

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Questions?

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Questions? jakewharton jakewharton jakewharton twitter.com/ google.com/+ .com

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