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Java example source code file (FactoryModuleBuilder.java)

This example Java source code file (FactoryModuleBuilder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractmodule, annotation, bindingcollector, class, factorymodulebuilder, factoryprovider2, key, override, typeliteral

The FactoryModuleBuilder.java Java example source code

/**
 * Copyright (C) 2009 Google Inc.
 *
 * 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 com.google.inject.assistedinject;

import com.google.inject.AbstractModule;
import com.google.inject.Key;
import com.google.inject.Module;
import com.google.inject.Provider;
import com.google.inject.TypeLiteral;

import java.lang.annotation.Annotation;

/**
 * Provides a factory that combines the caller's arguments with injector-supplied values to
 * construct objects.
 *
 * <h3>Defining a factory
 * Create an interface whose methods return the constructed type, or any of its supertypes. The
 * method's parameters are the arguments required to build the constructed type.
 *
 * <pre>public interface PaymentFactory {
 *   Payment create(Date startDate, Money amount);
 * }</pre>
 *
 * You can name your factory methods whatever you like, such as <i>create, createPayment
 * or <i>newPayment.
 *
 * <h3>Creating a type that accepts factory parameters
 * {@code constructedType} is a concrete class with an {@literal @}{@link com.google.inject.Inject
 * Inject}-annotated constructor. In addition to injector-supplied parameters, the constructor
 * should have parameters that match each of the factory method's parameters. Each factory-supplied
 * parameter requires an {@literal @}{@link Assisted} annotation. This serves to document that the
 * parameter is not bound by your application's modules.
 *
 * <pre>public class RealPayment implements Payment {
 *   {@literal @}Inject
 *   public RealPayment(
 *      CreditService creditService,
 *      AuthService authService,
 *      <strong>{@literal @}Assisted Date startDate,
 *      <strong>{@literal @}Assisted Money amount) {
 *     ...
 *   }
 * }</pre>
 * 
 * <h3>Multiple factory methods for the same type
 * If the factory contains many methods that return the same type, you can create multiple
 * constructors in your concrete class, each constructor marked with with
 * {@literal @}{@link AssistedInject}, in order to match the different parameters types of the
 * factory methods. 
 * 
 * <pre>public interface PaymentFactory {
 *    Payment create(Date startDate, Money amount);
 *    Payment createWithoutDate(Money amount);
 * }
 * 
 * public class RealPayment implements Payment {
 *  {@literal @}AssistedInject
 *   public RealPayment(
 *      CreditService creditService,
 *      AuthService authService,
 *     <strong>{@literal @}Assisted Date startDate,
 *     <strong>{@literal @}Assisted Money amount) {
 *     ...
 *   }
 *   
 *  {@literal @}AssistedInject
 *   public RealPayment(
 *      CreditService creditService,
 *      AuthService authService,
 *     <strong>{@literal @}Assisted Money amount) {
 *     ...
 *   }   
 * }</pre> 
 *
 * <h3>Configuring simple factories
 * In your {@link Module module}, install a {@code FactoryModuleBuilder} that creates the
 * factory:
 *
 * <pre>install(new FactoryModuleBuilder()
 *     .implement(Payment.class, RealPayment.class)
 *     .build(PaymentFactory.class));</pre>
 *
 * As a side-effect of this binding, Guice will inject the factory to initialize it for use. The
 * factory cannot be used until the injector has been initialized.
 * 
 * <h3>Configuring complex factories
 * Factories can create an arbitrary number of objects, one per each method.  Each factory
 * method can be configured using <code>.implement.
 *
 * <pre>public interface OrderFactory {
 *    Payment create(Date startDate, Money amount);
 *    Shipment create(Customer customer, Item item);
 *    Receipt create(Payment payment, Shipment shipment);
 * }
 * 
 * [...]
 * 
 * install(new FactoryModuleBuilder()
 *     .implement(Payment.class, RealPayment.class)
 *     // excluding .implement for Shipment means the implementation class
 *     // will be 'Shipment' itself, which is legal if it's not an interface.
 *     .implement(Receipt.class, RealReceipt.class)
 *     .build(OrderFactory.class));</pre>
 * </pre>
 *
 * <h3>Using the factory
 * Inject your factory into your application classes. When you use the factory, your arguments
 * will be combined with values from the injector to construct an instance.
 *
 * <pre>public class PaymentAction {
 *   {@literal @}Inject private PaymentFactory paymentFactory;
 *
 *   public void doPayment(Money amount) {
 *     Payment payment = paymentFactory.create(new Date(), amount);
 *     payment.apply();
 *   }
 * }</pre>
 *
 * <h3>Making parameter types distinct
 * The types of the factory method's parameters must be distinct. To use multiple parameters of
 * the same type, use a named {@literal @}{@link Assisted} annotation to disambiguate the
 * parameters. The names must be applied to the factory method's parameters:
 *
 * <pre>public interface PaymentFactory {
 *   Payment create(
 *       <strong>{@literal @}Assisted("startDate") Date startDate,
 *       <strong>{@literal @}Assisted("dueDate") Date dueDate,
 *       Money amount);
 * } </pre>
 *
 * ...and to the concrete type's constructor parameters:
 *
 * <pre>public class RealPayment implements Payment {
 *   {@literal @}Inject
 *   public RealPayment(
 *      CreditService creditService,
 *      AuthService authService,
 *      <strong>{@literal @}Assisted("startDate") Date startDate,
 *      <strong>{@literal @}Assisted("dueDate") Date dueDate,
 *      <strong>{@literal @}Assisted Money amount) {
 *     ...
 *   }
 * }</pre>
 *
 * <h3>Values are created by Guice
 * Returned factories use child injectors to create values. The values are eligible for method
 * interception. In addition, {@literal @}{@literal Inject} members will be injected before they are
 * returned.
 *
 * <h3>More configuration options
 * In addition to simply specifying an implementation class for any returned type, factories' return
 * values can be automatic or can be configured to use annotations:
 * <p/>
 * If you just want to return the types specified in the factory, do not configure any
 * implementations:
 *
 * <pre>public interface FruitFactory {
 *   Apple getApple(Color color);
 * }
 * ...
 * protected void configure() {
 *   install(new FactoryModuleBuilder().build(FruitFactory.class));
 * }</pre>
 *
 * Note that any type returned by the factory in this manner needs to be an implementation class.
 * <p/>
 * To return two different implementations for the same interface from your factory, use binding
 * annotations on your return types:
 *
 * <pre>interface CarFactory {
 *   {@literal @}Named("fast") Car getFastCar(Color color);
 *   {@literal @}Named("clean") Car getCleanCar(Color color);
 * }
 * ...
 * protected void configure() {
 *   install(new FactoryModuleBuilder()
 *       .implement(Car.class, Names.named("fast"), Porsche.class)
 *       .implement(Car.class, Names.named("clean"), Prius.class)
 *       .build(CarFactory.class));
 * }</pre>
 * 
 * <h3>Implementation limitations
 * As a limitation of the implementation, it is prohibited to declare a factory method that
 * accepts a {@code Provider} as one of its arguments.
 *
 * @since 3.0
 * @author schmitt@google.com (Peter Schmitt)
 */
public final class FactoryModuleBuilder {

  private final BindingCollector bindings = new BindingCollector();

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Class source, Class target) {
    return implement(source, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Class source, TypeLiteral target) {
    return implement(TypeLiteral.get(source), target);
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(TypeLiteral source, Class target) {
    return implement(source, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(TypeLiteral source,
      TypeLiteral<? extends T> target) {
    return implement(Key.get(source), target);
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Class source, Annotation annotation,
      Class<? extends T> target) {
    return implement(source, annotation, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Class source, Annotation annotation,
      TypeLiteral<? extends T> target) {
    return implement(TypeLiteral.get(source), annotation, target);
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(TypeLiteral source, Annotation annotation,
      Class<? extends T> target) {
    return implement(source, annotation, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(TypeLiteral source, Annotation annotation,
      TypeLiteral<? extends T> target) {
    return implement(Key.get(source, annotation), target);
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Class source,
      Class<? extends Annotation> annotationType, Class target) {
    return implement(source, annotationType, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Class source,
      Class<? extends Annotation> annotationType, TypeLiteral target) {
    return implement(TypeLiteral.get(source), annotationType, target);
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(TypeLiteral source,
      Class<? extends Annotation> annotationType, Class target) {
    return implement(source, annotationType, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(TypeLiteral source,
      Class<? extends Annotation> annotationType, TypeLiteral target) {
    return implement(Key.get(source, annotationType), target);
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Key source, Class target) {
    return implement(source, TypeLiteral.get(target));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <T> FactoryModuleBuilder implement(Key source, TypeLiteral target) {
    bindings.addBinding(source, target);
    return this;
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <F> Module build(Class factoryInterface) {
    return build(TypeLiteral.get(factoryInterface));
  }

  /**
   * See the factory configuration examples at {@link FactoryModuleBuilder}.
   */
  public <F> Module build(TypeLiteral factoryInterface) {
    return build(Key.get(factoryInterface));
  }


  public <F> Module build(final Key factoryInterface) {
    return new AbstractModule() {
      @Override protected void configure() {
        Provider<F> provider = new FactoryProvider2(factoryInterface, bindings);
        bind(factoryInterface).toProvider(provider);
      }
    };
  }
}

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