1 /** 2 * Copyright (C) 2009 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 17 package com.google.inject.spi; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 import static com.google.common.base.Preconditions.checkState; 21 22 import com.google.inject.Binder; 23 import com.google.inject.MembersInjector; 24 import com.google.inject.TypeLiteral; 25 26 /** 27 * A lookup of the members injector for a type. Lookups are created explicitly in a module using 28 * {@link com.google.inject.Binder#getMembersInjector(Class) getMembersInjector()} statements: 29 * <pre> 30 * MembersInjector<PaymentService> membersInjector 31 * = getMembersInjector(PaymentService.class);</pre> 32 * 33 * @author crazybob (at) google.com (Bob Lee) 34 * @since 2.0 35 */ 36 public final class MembersInjectorLookup<T> implements Element { 37 38 private final Object source; 39 private final TypeLiteral<T> type; 40 private MembersInjector<T> delegate; 41 42 public MembersInjectorLookup(Object source, TypeLiteral<T> type) { 43 this.source = checkNotNull(source, "source"); 44 this.type = checkNotNull(type, "type"); 45 } 46 47 public Object getSource() { 48 return source; 49 } 50 51 /** 52 * Gets the type containing the members to be injected. 53 */ 54 public TypeLiteral<T> getType() { 55 return type; 56 } 57 58 public <T> T acceptVisitor(ElementVisitor<T> visitor) { 59 return visitor.visit(this); 60 } 61 62 /** 63 * Sets the actual members injector. 64 * 65 * @throws IllegalStateException if the delegate is already set 66 */ 67 public void initializeDelegate(MembersInjector<T> delegate) { 68 checkState(this.delegate == null, "delegate already initialized"); 69 this.delegate = checkNotNull(delegate, "delegate"); 70 } 71 72 public void applyTo(Binder binder) { 73 initializeDelegate(binder.withSource(getSource()).getMembersInjector(type)); 74 } 75 76 /** 77 * Returns the delegate members injector, or {@code null} if it has not yet been initialized. 78 * The delegate will be initialized when this element is processed, or otherwise used to create 79 * an injector. 80 */ 81 public MembersInjector<T> getDelegate() { 82 return delegate; 83 } 84 85 /** 86 * Returns the looked up members injector. The result is not valid until this lookup has been 87 * initialized, which usually happens when the injector is created. The members injector will 88 * throw an {@code IllegalStateException} if you try to use it beforehand. 89 */ 90 public MembersInjector<T> getMembersInjector() { 91 return new MembersInjector<T>() { 92 public void injectMembers(T instance) { 93 checkState(delegate != null, 94 "This MembersInjector cannot be used until the Injector has been created."); 95 delegate.injectMembers(instance); 96 } 97 98 @Override public String toString() { 99 return "MembersInjector<" + type + ">"; 100 } 101 }; 102 } 103 }
