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 * 30 * <pre> 31 * MembersInjector<PaymentService> membersInjector 32 * = getMembersInjector(PaymentService.class);</pre> 33 * 34 * @author crazybob@google.com (Bob Lee) 35 * @since 2.0 36 */ 37 public final class MembersInjectorLookup<T> implements Element { 38 39 private final Object source; 40 private final TypeLiteral<T> type; 41 private MembersInjector<T> delegate; 42 MembersInjectorLookup(Object source, TypeLiteral<T> type)43 public MembersInjectorLookup(Object source, TypeLiteral<T> type) { 44 this.source = checkNotNull(source, "source"); 45 this.type = checkNotNull(type, "type"); 46 } 47 48 @Override getSource()49 public Object getSource() { 50 return source; 51 } 52 53 /** Gets the type containing the members to be injected. */ getType()54 public TypeLiteral<T> getType() { 55 return type; 56 } 57 58 @Override acceptVisitor(ElementVisitor<T> visitor)59 public <T> T acceptVisitor(ElementVisitor<T> visitor) { 60 return visitor.visit(this); 61 } 62 63 /** 64 * Sets the actual members injector. 65 * 66 * @throws IllegalStateException if the delegate is already set 67 */ initializeDelegate(MembersInjector<T> delegate)68 public void initializeDelegate(MembersInjector<T> delegate) { 69 checkState(this.delegate == null, "delegate already initialized"); 70 this.delegate = checkNotNull(delegate, "delegate"); 71 } 72 73 @Override applyTo(Binder binder)74 public void applyTo(Binder binder) { 75 initializeDelegate(binder.withSource(getSource()).getMembersInjector(type)); 76 } 77 78 /** 79 * Returns the delegate members injector, or {@code null} if it has not yet been initialized. The 80 * delegate will be initialized when this element is processed, or otherwise used to create an 81 * injector. 82 */ getDelegate()83 public MembersInjector<T> getDelegate() { 84 return delegate; 85 } 86 87 /** 88 * Returns the looked up members injector. The result is not valid until this lookup has been 89 * initialized, which usually happens when the injector is created. The members injector will 90 * throw an {@code IllegalStateException} if you try to use it beforehand. 91 */ getMembersInjector()92 public MembersInjector<T> getMembersInjector() { 93 return new MembersInjector<T>() { 94 @Override 95 public void injectMembers(T instance) { 96 MembersInjector<T> local = delegate; 97 if (local == null) { 98 throw new IllegalStateException( 99 "This MembersInjector cannot be used until the Injector has been created."); 100 } 101 local.injectMembers(instance); 102 } 103 104 @Override 105 public String toString() { 106 return "MembersInjector<" + type + ">"; 107 } 108 }; 109 } 110 } 111