| /** |
| * 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.spi; |
| |
| import com.google.inject.Binder; |
| import com.google.inject.Key; |
| import com.google.inject.Provider; |
| import static com.google.inject.internal.util.Preconditions.checkNotNull; |
| import static com.google.inject.internal.util.Preconditions.checkState; |
| |
| /** |
| * A lookup of the provider for a type. Lookups are created explicitly in a module using |
| * {@link com.google.inject.Binder#getProvider(Class) getProvider()} statements: |
| * <pre> |
| * Provider<PaymentService> paymentServiceProvider |
| * = getProvider(PaymentService.class);</pre> |
| * |
| * @author jessewilson@google.com (Jesse Wilson) |
| * @since 2.0 |
| */ |
| public final class ProviderLookup<T> implements Element { |
| private final Object source; |
| private final Key<T> key; |
| private Provider<T> delegate; |
| |
| public ProviderLookup(Object source, Key<T> key) { |
| this.source = checkNotNull(source, "source"); |
| this.key = checkNotNull(key, "key"); |
| } |
| |
| public Object getSource() { |
| return source; |
| } |
| |
| public Key<T> getKey() { |
| return key; |
| } |
| |
| public <T> T acceptVisitor(ElementVisitor<T> visitor) { |
| return visitor.visit(this); |
| } |
| |
| /** |
| * Sets the actual provider. |
| * |
| * @throws IllegalStateException if the delegate is already set |
| */ |
| public void initializeDelegate(Provider<T> delegate) { |
| checkState(this.delegate == null, "delegate already initialized"); |
| this.delegate = checkNotNull(delegate, "delegate"); |
| } |
| |
| public void applyTo(Binder binder) { |
| initializeDelegate(binder.withSource(getSource()).getProvider(key)); |
| } |
| |
| /** |
| * Returns the delegate provider, or {@code null} if it has not yet been initialized. The delegate |
| * will be initialized when this element is processed, or otherwise used to create an injector. |
| */ |
| public Provider<T> getDelegate() { |
| return delegate; |
| } |
| |
| /** |
| * Returns the looked up provider. The result is not valid until this lookup has been initialized, |
| * which usually happens when the injector is created. The provider will throw an {@code |
| * IllegalStateException} if you try to use it beforehand. |
| */ |
| public Provider<T> getProvider() { |
| return new Provider<T>() { |
| public T get() { |
| checkState(delegate != null, |
| "This Provider cannot be used until the Injector has been created."); |
| return delegate.get(); |
| } |
| |
| @Override public String toString() { |
| return "Provider<" + key.getTypeLiteral() + ">"; |
| } |
| }; |
| } |
| } |