1 /*
2  * Copyright (C) 2015 Google Inc.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package com.google.inject.daggeradapter;
17 
18 import com.google.common.base.MoreObjects;
19 import com.google.inject.Binder;
20 import com.google.inject.Module;
21 import com.google.inject.internal.ProviderMethodsModule;
22 import com.google.inject.spi.ModuleAnnotatedMethodScanner;
23 import java.util.Arrays;
24 
25 /**
26  * A utility to adapt classes annotated with {@link @dagger.Module} such that their
27  * {@link @dagger.Provides} methods can be properly invoked by Guice to perform their provision
28  * operations.
29  *
30  * <p>Simple example:
31  *
32  * <pre>{@code
33  * Guice.createInjector(...other modules..., DaggerAdapter.from(new SomeDaggerAdapter()));
34  * }</pre>
35  *
36  * <p>Some notes on usage and compatibility.
37  *
38  * <ul>
39  * <li>Dagger provider methods have a "SET_VALUES" provision mode not supported by Guice.
40  * <li>MapBindings are not yet implemented (pending).
41  * <li>Be careful about stateful modules. In contrast to Dagger (where components are expected to be
42  *     recreated on-demand with new Module instances), Guice typically has a single injector with a
43  *     long lifetime, so your module instance will be used throughout the lifetime of the entire
44  *     app.
45  * <li>Dagger 1.x uses {@link @Singleton} for all scopes, including shorter-lived scopes like
46  *     per-request or per-activity. Using modules written with Dagger 1.x usage in mind may result
47  *     in mis-scoped objects.
48  * <li>Dagger 2.x supports custom scope annotations, but for use in Guice, a custom scope
49  *     implementation must be registered in order to support the custom lifetime of that annotation.
50  * </ul>
51  *
52  * @author cgruber@google.com (Christian Gruber)
53  */
54 public final class DaggerAdapter {
55   /**
56    * Returns a guice module from a dagger module.
57    *
58    * <p>Note: At present, it does not honor {@code @Module(includes=...)} directives.
59    */
from(Object... daggerModuleObjects)60   public static Module from(Object... daggerModuleObjects) {
61     // TODO(cgruber): Gather injects=, dedupe, factor out instances, instantiate the rest, and go.
62     return new DaggerCompatibilityModule(daggerModuleObjects);
63   }
64 
65   /**
66    * A Module that adapts Dagger {@code @Module}-annotated types to contribute configuration to an
67    * {@link com.google.inject.Injector} using a dagger-specific {@link
68    * ModuleAnnotatedMethodScanner}.
69    */
70   private static final class DaggerCompatibilityModule implements Module {
71     private final Object[] daggerModuleObjects;
72 
DaggerCompatibilityModule(Object... daggerModuleObjects)73     private DaggerCompatibilityModule(Object... daggerModuleObjects) {
74       this.daggerModuleObjects = daggerModuleObjects;
75     }
76 
77     @Override
configure(Binder binder)78     public void configure(Binder binder) {
79       for (Object module : daggerModuleObjects) {
80         binder.install(ProviderMethodsModule.forModule(module, DaggerMethodScanner.INSTANCE));
81       }
82     }
83 
84     @Override
toString()85     public String toString() {
86       return MoreObjects.toStringHelper(this)
87           .add("modules", Arrays.asList(daggerModuleObjects))
88           .toString();
89     }
90   }
91 
DaggerAdapter()92   private DaggerAdapter() {}
93 }
94