| /** |
| * Copyright (C) 2008 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.multibindings; |
| |
| import com.google.common.collect.ImmutableList; |
| import com.google.common.collect.ImmutableSet; |
| import com.google.inject.Binder; |
| import com.google.inject.Binding; |
| import com.google.inject.ConfigurationException; |
| import com.google.inject.Inject; |
| import com.google.inject.Injector; |
| import com.google.inject.Key; |
| import com.google.inject.Module; |
| import com.google.inject.Provider; |
| import com.google.inject.TypeLiteral; |
| import com.google.inject.binder.LinkedBindingBuilder; |
| import com.google.inject.internal.Errors; |
| import com.google.inject.spi.Message; |
| import com.google.inject.util.Types; |
| import java.lang.annotation.Annotation; |
| import java.lang.reflect.Type; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.LinkedHashSet; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * An API to bind multiple values separately, only to later inject them as a |
| * complete collection. Multibinder is intended for use in your application's |
| * module: |
| * <pre><code> |
| * public class SnacksModule extends AbstractModule { |
| * protected void configure() { |
| * Multibinder<Snack> multibinder |
| * = Multibinder.newSetBinder(binder(), Snack.class); |
| * multibinder.addBinding().toInstance(new Twix()); |
| * multibinder.addBinding().toProvider(SnickersProvider.class); |
| * multibinder.addBinding().to(Skittles.class); |
| * } |
| * }</code></pre> |
| * |
| * <p>With this binding, a {@link Set}{@code <Snack>} can now be injected: |
| * <pre><code> |
| * class SnackMachine { |
| * {@literal @}Inject |
| * public SnackMachine(Set<Snack> snacks) { ... } |
| * }</code></pre> |
| * |
| * <p>Create multibindings from different modules is supported. For example, it |
| * is okay to have both {@code CandyModule} and {@code ChipsModule} to both |
| * create their own {@code Multibinder<Snack>}, and to each contribute bindings |
| * to the set of snacks. When that set is injected, it will contain elements |
| * from both modules. |
| * |
| * <p>Elements are resolved at set injection time. If an element is bound to a |
| * provider, that provider's get method will be called each time the set is |
| * injected (unless the binding is also scoped). |
| * |
| * <p>Annotations are be used to create different sets of the same element |
| * type. Each distinct annotation gets its own independent collection of |
| * elements. |
| * |
| * <p><strong>Elements must be distinct.</strong> If multiple bound elements |
| * have the same value, set injection will fail. |
| * |
| * <p><strong>Elements must be non-null.</strong> If any set element is null, |
| * set injection will fail. |
| * |
| * @author jessewilson@google.com (Jesse Wilson) |
| */ |
| public abstract class Multibinder<T> { |
| private Multibinder() {} |
| |
| /** |
| * Returns a new multibinder that collects instances of {@code type} in a {@link Set} that is |
| * itself bound with no binding annotation. |
| */ |
| public static <T> Multibinder<T> newSetBinder(Binder binder, TypeLiteral<T> type) { |
| binder = binder.skipSources(RealMultibinder.class, Multibinder.class); |
| RealMultibinder<T> result = new RealMultibinder<T>(binder, type, "", |
| Key.get(Multibinder.<T>setOf(type))); |
| binder.install(result); |
| return result; |
| } |
| |
| /** |
| * Returns a new multibinder that collects instances of {@code type} in a {@link Set} that is |
| * itself bound with no binding annotation. |
| */ |
| public static <T> Multibinder<T> newSetBinder(Binder binder, Class<T> type) { |
| return newSetBinder(binder, TypeLiteral.get(type)); |
| } |
| |
| /** |
| * Returns a new multibinder that collects instances of {@code type} in a {@link Set} that is |
| * itself bound with {@code annotation}. |
| */ |
| public static <T> Multibinder<T> newSetBinder( |
| Binder binder, TypeLiteral<T> type, Annotation annotation) { |
| binder = binder.skipSources(RealMultibinder.class, Multibinder.class); |
| RealMultibinder<T> result = new RealMultibinder<T>(binder, type, annotation.toString(), |
| Key.get(Multibinder.<T>setOf(type), annotation)); |
| binder.install(result); |
| return result; |
| } |
| |
| /** |
| * Returns a new multibinder that collects instances of {@code type} in a {@link Set} that is |
| * itself bound with {@code annotation}. |
| */ |
| public static <T> Multibinder<T> newSetBinder( |
| Binder binder, Class<T> type, Annotation annotation) { |
| return newSetBinder(binder, TypeLiteral.get(type), annotation); |
| } |
| |
| /** |
| * Returns a new multibinder that collects instances of {@code type} in a {@link Set} that is |
| * itself bound with {@code annotationType}. |
| */ |
| public static <T> Multibinder<T> newSetBinder(Binder binder, TypeLiteral<T> type, |
| Class<? extends Annotation> annotationType) { |
| binder = binder.skipSources(RealMultibinder.class, Multibinder.class); |
| RealMultibinder<T> result = new RealMultibinder<T>(binder, type, "@" + annotationType.getName(), |
| Key.get(Multibinder.<T>setOf(type), annotationType)); |
| binder.install(result); |
| return result; |
| } |
| |
| /** |
| * Returns a new multibinder that collects instances of {@code type} in a {@link Set} that is |
| * itself bound with {@code annotationType}. |
| */ |
| public static <T> Multibinder<T> newSetBinder(Binder binder, Class<T> type, |
| Class<? extends Annotation> annotationType) { |
| return newSetBinder(binder, TypeLiteral.get(type), annotationType); |
| } |
| |
| @SuppressWarnings("unchecked") // wrapping a T in a Set safely returns a Set<T> |
| private static <T> TypeLiteral<Set<T>> setOf(TypeLiteral<T> elementType) { |
| Type type = Types.setOf(elementType.getType()); |
| return (TypeLiteral<Set<T>>) TypeLiteral.get(type); |
| } |
| |
| /** |
| * Returns a binding builder used to add a new element in the set. Each |
| * bound element must have a distinct value. Bound providers will be |
| * evaluated each time the set is injected. |
| * |
| * <p>It is an error to call this method without also calling one of the |
| * {@code to} methods on the returned binding builder. |
| * |
| * <p>Scoping elements independently is supported. Use the {@code in} method |
| * to specify a binding scope. |
| */ |
| public abstract LinkedBindingBuilder<T> addBinding(); |
| |
| /** |
| * The actual multibinder plays several roles: |
| * |
| * <p>As a Multibinder, it acts as a factory for LinkedBindingBuilders for |
| * each of the set's elements. Each binding is given an annotation that |
| * identifies it as a part of this set. |
| * |
| * <p>As a Module, it installs the binding to the set itself. As a module, |
| * this implements equals() and hashcode() in order to trick Guice into |
| * executing its configure() method only once. That makes it so that |
| * multiple multibinders can be created for the same target collection, but |
| * only one is bound. Since the list of bindings is retrieved from the |
| * injector itself (and not the multibinder), each multibinder has access to |
| * all contributions from all multibinders. |
| * |
| * <p>As a Provider, this constructs the set instances. |
| * |
| * <p>We use a subclass to hide 'implements Module, Provider' from the public |
| * API. |
| */ |
| static final class RealMultibinder<T> extends Multibinder<T> implements Module, Provider<Set<T>> { |
| |
| private final TypeLiteral<T> elementType; |
| private final String setName; |
| private final Key<Set<T>> setKey; |
| |
| /* the target injector's binder. non-null until initialization, null afterwards */ |
| private Binder binder; |
| |
| /* a provider for each element in the set. null until initialization, non-null afterwards */ |
| private List<Provider<T>> providers; |
| |
| private RealMultibinder(Binder binder, TypeLiteral<T> elementType, |
| String setName, Key<Set<T>> setKey) { |
| this.binder = checkNotNull(binder, "binder"); |
| this.elementType = checkNotNull(elementType, "elementType"); |
| this.setName = checkNotNull(setName, "setName"); |
| this.setKey = checkNotNull(setKey, "setKey"); |
| } |
| |
| @SuppressWarnings("unchecked") |
| public void configure(Binder binder) { |
| checkConfiguration(!isInitialized(), "Multibinder was already initialized"); |
| |
| binder.bind(setKey).toProvider(this); |
| } |
| |
| @Override public LinkedBindingBuilder<T> addBinding() { |
| checkConfiguration(!isInitialized(), "Multibinder was already initialized"); |
| |
| return binder.bind(Key.get(elementType, new RealElement(setName))); |
| } |
| |
| /** |
| * Invoked by Guice at Injector-creation time to prepare providers for each |
| * element in this set. At this time the set's size is known, but its |
| * contents are only evaluated when get() is invoked. |
| */ |
| @Inject void initialize(Injector injector) { |
| providers = new ArrayList<Provider<T>>(); |
| for (Map.Entry<Key<?>, Binding<?>> entry : injector.getBindings().entrySet()) { |
| if (keyMatches(entry.getKey())) { |
| @SuppressWarnings("unchecked") |
| Binding<T> binding = (Binding<T>) entry.getValue(); |
| providers.add(binding.getProvider()); |
| } |
| } |
| |
| this.binder = null; |
| } |
| |
| private boolean keyMatches(Key<?> key) { |
| return key.getTypeLiteral().equals(elementType) |
| && key.getAnnotation() instanceof Element |
| && ((Element) key.getAnnotation()).setName().equals(setName); |
| } |
| |
| private boolean isInitialized() { |
| return binder == null; |
| } |
| |
| public Set<T> get() { |
| checkConfiguration(isInitialized(), "Multibinder is not initialized"); |
| |
| Set<T> result = new LinkedHashSet<T>(); |
| for (Provider<T> provider : providers) { |
| final T newValue = provider.get(); |
| checkConfiguration(newValue != null, "Set injection failed due to null element"); |
| checkConfiguration(result.add(newValue), |
| "Set injection failed due to duplicated element \"%s\"", newValue); |
| } |
| return Collections.unmodifiableSet(result); |
| } |
| |
| String getSetName() { |
| return setName; |
| } |
| |
| Key<Set<T>> getSetKey() { |
| return setKey; |
| } |
| |
| @Override public boolean equals(Object o) { |
| return o instanceof RealMultibinder |
| && ((RealMultibinder<?>) o).setKey.equals(setKey); |
| } |
| |
| @Override public int hashCode() { |
| return setKey.hashCode(); |
| } |
| |
| @Override public String toString() { |
| return new StringBuilder() |
| .append(setName) |
| .append(setName.length() > 0 ? " " : "") |
| .append("Multibinder<") |
| .append(elementType) |
| .append(">") |
| .toString(); |
| } |
| } |
| |
| static void checkConfiguration(boolean condition, String format, Object... args) { |
| if (condition) { |
| return; |
| } |
| |
| throw new ConfigurationException(ImmutableSet.of(new Message(Errors.format(format, args)))); |
| } |
| |
| static <T> T checkNotNull(T reference, String name) { |
| if (reference != null) { |
| return reference; |
| } |
| |
| NullPointerException npe = new NullPointerException(name); |
| throw new ConfigurationException(ImmutableSet.of( |
| new Message(ImmutableList.of(), npe.toString(), npe))); |
| } |
| } |