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Java example source code file (DaggerAdapter.java)

This example Java source code file (DaggerAdapter.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

daggeradapter, daggercompatibilitymodule, module, object, override, string, util

The DaggerAdapter.java Java example source code

/**
 * Copyright (C) 2015 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.daggeradapter;

import com.google.common.base.MoreObjects;
import com.google.inject.Binder;
import com.google.inject.Module;
import com.google.inject.internal.ProviderMethodsModule;
import com.google.inject.spi.ModuleAnnotatedMethodScanner;

import java.util.Arrays;

/**
 * A utility to adapt classes annotated with {@link @dagger.Module} such that their
 * {@link @dagger.Provides} methods can be properly invoked by Guice to perform their
 * provision operations.
 *
 * <p>Simple example: 
{@code
 *   Guice.createInjector(...other modules..., DaggerAdapter.from(new SomeDaggerAdapter()));
 * }</pre>
 *
 * <p>Some notes on usage and compatibility.
 *   <ul>
 *     <li>Dagger provider methods have a "SET_VALUES" provision mode not supported by Guice.
 *     <li>MapBindings are not yet implemented (pending).
 *     <li>Be careful about stateful modules. In contrast to Dagger (where components are
 *         expected to be recreated on-demand with new Module instances), Guice typically
 *         has a single injector with a long lifetime, so your module instance will be used
 *         throughout the lifetime of the entire app.
 *     <li>Dagger 1.x uses {@link @Singleton} for all scopes, including shorter-lived scopes
 *         like per-request or per-activity.  Using modules written with Dagger 1.x usage
 *         in mind may result in mis-scoped objects.
 *     <li>Dagger 2.x supports custom scope annotations, but for use in Guice, a custom scope
 *         implementation must be registered in order to support the custom lifetime of that
 *         annotation.
 *   </ul>
 *
 * @author cgruber@google.com (Christian Gruber)
 */
public final class DaggerAdapter {
  /**
   * Returns a guice module from a dagger module.
   *
   * <p>Note: At present, it does not honor {@code @Module(includes=...)} directives.
   */
  public static Module from(Object... daggerModuleObjects) {
    // TODO(cgruber): Gather injects=, dedupe, factor out instances, instantiate the rest, and go.
    return new DaggerCompatibilityModule(daggerModuleObjects);
  }

  /**
   * A Module that adapts Dagger {@code @Module}-annotated types to contribute configuration
   * to an {@link com.google.inject.Injector} using a dagger-specific
   * {@link ModuleAnnotatedMethodScanner}.
   */
  private static final class DaggerCompatibilityModule implements Module {
    private final Object[] daggerModuleObjects;

    private DaggerCompatibilityModule(Object... daggerModuleObjects) {
      this.daggerModuleObjects = daggerModuleObjects;
    }

    @Override public void configure(Binder binder) {
      for (Object module : daggerModuleObjects) {
        binder.install(ProviderMethodsModule.forModule(module, DaggerMethodScanner.INSTANCE));
      }
    }

    @Override public String toString() {
      return MoreObjects.toStringHelper(this)
          .add("modules", Arrays.asList(daggerModuleObjects))
          .toString();
    }
  }

  private DaggerAdapter() {}
}

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