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
17package com.google.inject.internal;
18
19
20import com.google.common.base.Preconditions;
21
22import java.lang.reflect.InvocationHandler;
23import java.lang.reflect.InvocationTargetException;
24import java.lang.reflect.Method;
25
26class DelegatingInvocationHandler<T> implements InvocationHandler {
27
28  private volatile boolean initialized;
29
30  private T delegate;
31
32  public Object invoke(Object proxy, Method method, Object[] args)
33      throws Throwable {
34    try {
35      // checking volatile field for synchronization
36      Preconditions.checkState(initialized,
37          "This is a proxy used to support"
38              + " circular references. The object we're"
39              + " proxying is not constructed yet. Please wait until after"
40              + " injection has completed to use this object.");
41      Preconditions.checkNotNull(delegate,
42          "This is a proxy used to support"
43              + " circular references. The object we're "
44              + " proxying is initialized to null."
45              + " No methods can be called.");
46
47      // TODO: method.setAccessible(true); ?
48      // this would fix visibility errors when we proxy a
49      // non-public interface.
50      return method.invoke(delegate, args);
51    } catch (IllegalAccessException e) {
52      throw new RuntimeException(e);
53    } catch (IllegalArgumentException e) {
54      throw new RuntimeException(e);
55    } catch (InvocationTargetException e) {
56      throw e.getTargetException();
57    }
58  }
59
60  void setDelegate(T delegate) {
61    this.delegate = delegate;
62    initialized = true;
63  }
64}
65