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      1 /**
      2  * Copyright (C) 2006 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.internal;
     18 
     19 import com.google.common.base.Objects;
     20 import com.google.inject.Binding;
     21 import com.google.inject.Key;
     22 import com.google.inject.Provider;
     23 import com.google.inject.spi.BindingScopingVisitor;
     24 import com.google.inject.spi.ElementVisitor;
     25 import com.google.inject.spi.InstanceBinding;
     26 
     27 /**
     28  * @author crazybob (at) google.com (Bob Lee)
     29  */
     30 public abstract class BindingImpl<T> implements Binding<T> {
     31 
     32   private final InjectorImpl injector;
     33   private final Key<T> key;
     34   private final Object source;
     35   private final Scoping scoping;
     36   private final InternalFactory<? extends T> internalFactory;
     37 
     38   public BindingImpl(InjectorImpl injector, Key<T> key, Object source,
     39       InternalFactory<? extends T> internalFactory, Scoping scoping) {
     40     this.injector = injector;
     41     this.key = key;
     42     this.source = source;
     43     this.internalFactory = internalFactory;
     44     this.scoping = scoping;
     45   }
     46 
     47   protected BindingImpl(Object source, Key<T> key, Scoping scoping) {
     48     this.internalFactory = null;
     49     this.injector = null;
     50     this.source = source;
     51     this.key = key;
     52     this.scoping = scoping;
     53   }
     54 
     55   public Key<T> getKey() {
     56     return key;
     57   }
     58 
     59   public Object getSource() {
     60     return source;
     61   }
     62 
     63   private volatile Provider<T> provider;
     64 
     65   public Provider<T> getProvider() {
     66     if (provider == null) {
     67       if (injector == null) {
     68         throw new UnsupportedOperationException("getProvider() not supported for module bindings");
     69       }
     70 
     71       provider = injector.getProvider(key);
     72     }
     73     return provider;
     74   }
     75 
     76   public InternalFactory<? extends T> getInternalFactory() {
     77     return internalFactory;
     78   }
     79 
     80   public Scoping getScoping() {
     81     return scoping;
     82   }
     83 
     84   /**
     85    * Is this a constant binding? This returns true for constant bindings as
     86    * well as toInstance() bindings.
     87    */
     88   public boolean isConstant() {
     89     return this instanceof InstanceBinding;
     90   }
     91 
     92   public <V> V acceptVisitor(ElementVisitor<V> visitor) {
     93     return visitor.visit(this);
     94   }
     95 
     96   public <V> V acceptScopingVisitor(BindingScopingVisitor<V> visitor) {
     97     return scoping.acceptVisitor(visitor);
     98   }
     99 
    100   protected BindingImpl<T> withScoping(Scoping scoping) {
    101     throw new AssertionError();
    102   }
    103 
    104   protected BindingImpl<T> withKey(Key<T> key) {
    105     throw new AssertionError();
    106   }
    107 
    108   @Override public String toString() {
    109     return Objects.toStringHelper(Binding.class)
    110         .add("key", key)
    111         .add("scope", scoping)
    112         .add("source", source)
    113         .toString();
    114   }
    115 
    116   public InjectorImpl getInjector() {
    117     return injector;
    118   }
    119 }
    120