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A fast dependency injector for Android and Java.
There is a newer version: 2.52
/*
 * Copyright (C) 2014 The Dagger Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package dagger.producers;

import static java.lang.annotation.ElementType.TYPE;

import com.google.common.util.concurrent.ListenableFuture;
import dagger.Module;
import dagger.Provides;
import dagger.internal.Beta;
import java.lang.annotation.Documented;
import java.lang.annotation.Target;
import javax.inject.Inject;
import javax.inject.Qualifier;

/**
 * Annotates an interface or abstract class for which a fully-formed, dependency-injected
 * implementation is to be generated from a set of {@linkplain #modules modules}. The generated
 * class will have the name of the type annotated with {@code @ProductionComponent} prepended with
 * {@code Dagger}.  For example, {@code @ProductionComponent interface MyComponent {...}} will
 * produce an implementation named {@code DaggerMyComponent}.
 *
 * Each {@link Produces} method that contributes to the component will be called at most once per
 * component instance, no matter how many times that binding is used as a dependency.
 * TODO(beder): Decide on how scope works for producers.
 *
 * 
Component methods
 *
 * Every type annotated with {@code @ProductionComponent} must contain at least one abstract
 * component method. Component methods must represent {@linkplain Producer production}.
 *
 * Production methods have no arguments and return either a {@link ListenableFuture} or
 * {@link Producer} of a type that is {@link Inject injected}, {@link Provides provided}, or
 * {@link Produces produced}. Each may have a {@link Qualifier} annotation as well. The following
 * are all valid production method declarations: 

 *   {@literal ListenableFuture} getSomeType();
 *   {@literal Producer>} getSomeTypes();
 *   {@literal @Response ListenableFuture} getResponse();
 * 
 *
 * Exceptions
 *
 * When a producer throws an exception, the exception will be propagated to its downstream
 * producers in the following way: if the downstream producer injects a type {@code T}, then that
 * downstream producer will be skipped, and the exception propagated to its downstream producers;
 * and if the downstream producer injects a {@code Produced}, then the downstream producer will
 * be run with the exception stored in the {@code Produced}.
 *
 * 
If a non-execution exception is thrown (e.g., an {@code InterruptedException} or
 * {@code CancellationException}), then exception is handled as in
 * {@link com.google.common.util.concurrent.Futures#transform}.
 * 
 *
 * 
Executor
 *
 * The component must include a binding for {@literal @}{@link Production}
 * {@link java.util.concurrent.Executor}; this binding will be called exactly once, and the
 * provided executor will be used by the framework to schedule all producer methods (for this
 * component, and any {@link ProductionSubcomponent} it may have.
 *
 * @since 2.0
 */
@Documented
@Target(TYPE)
@Beta
public @interface ProductionComponent {
  /**
   * A list of classes annotated with {@link Module} or {@link ProducerModule} whose bindings are
   * used to generate the component implementation.
   */
  Class[] modules() default {};

  /**
   * A list of types that are to be used as component dependencies.
   */
  Class[] dependencies() default {};

  /**
   * A builder for a component. Components may have a single nested static abstract class or
   * interface annotated with {@code @ProductionComponent.Builder}. If they do, then the component's
   * generated builder will match the API in the type.  Builders must follow some rules:
   * 

   *  A single abstract method with no arguments must exist, and must return the component.
   *      (This is typically the {@code build()} method.)
   * 
 All other abstract methods must take a single argument and must return void,
   *      the builder type, or a supertype of the builder.
   * 
 Each component dependency must have an abstract setter method.
   * 
 Each module dependency that Dagger can't instantiate itself (i.e., the module
   *      doesn't have a visible no-args constructor) must have an abstract setter method.
   *      Other module dependencies (ones that Dagger can instantiate) are allowed, but not
   *      required.
   * 
 Non-abstract methods are allowed, but ignored as far as validation and builder generation
   *      are concerned.
   * 
   *
   * For example, this could be a valid {@code ProductionComponent} with a builder: 
   * {@literal @}ProductionComponent(modules = {BackendModule.class, FrontendModule.class})
   * interface MyComponent {
   *   {@literal ListenableFuture} myWidget();
   *
   *   {@literal @}ProductionComponent.Builder
   *   interface Builder {
   *     MyComponent build();
   *     Builder backendModule(BackendModule bm);
   *     Builder frontendModule(FrontendModule fm);
   *   }
   * }
   */
  @Target(TYPE)
  @Documented
  @interface Builder {}
}