ProvisionListenerStackCallback.java revision ba0cff043c4412778856a45381dd35e02e30235c 
1/**
2 * Copyright (C) 2011 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
19import com.google.common.collect.ImmutableList;
20import com.google.common.collect.Sets;
21import com.google.inject.Binding;
22import com.google.inject.ProvisionException;
23import com.google.inject.spi.DependencyAndSource;
24import com.google.inject.spi.ProvisionListener;
25
26import java.util.List;
27import java.util.Set;
28
29/**
30 * Intercepts provisions with a stack of listeners.
31 *
32 * @author sameb@google.com (Sam Berlin)
33 */
34final class ProvisionListenerStackCallback<T> {
35
36  private static final ProvisionListener EMPTY_LISTENER[] = new ProvisionListener[0];
37  @SuppressWarnings("rawtypes")
38  private static final ProvisionListenerStackCallback<?> EMPTY_CALLBACK =
39      new ProvisionListenerStackCallback(null /* unused, so ok */, ImmutableList.of());
40
41  private final ProvisionListener[] listeners;
42  private final Binding<T> binding;
43
44  @SuppressWarnings("unchecked")
45  public static <T> ProvisionListenerStackCallback<T> emptyListener() {
46    return (ProvisionListenerStackCallback<T>) EMPTY_CALLBACK;
47  }
48
49  public ProvisionListenerStackCallback(Binding<T> binding, List<ProvisionListener> listeners) {
50    this.binding = binding;
51    if (listeners.isEmpty()) {
52      this.listeners = EMPTY_LISTENER;
53    } else {
54      Set<ProvisionListener> deDuplicated = Sets.newLinkedHashSet(listeners);
55      this.listeners = deDuplicated.toArray(new ProvisionListener[deDuplicated.size()]);
56    }
57  }
58
59  public boolean hasListeners() {
60    return listeners.length > 0;
61  }
62
63  public T provision(Errors errors, InternalContext context, ProvisionCallback<T> callable)
64      throws ErrorsException {
65    Provision provision = new Provision(errors, context, callable);
66    RuntimeException caught = null;
67    try {
68      provision.provision();
69    } catch(RuntimeException t) {
70      caught = t;
71    }
72
73    if (provision.exceptionDuringProvision != null) {
74      throw provision.exceptionDuringProvision;
75    } else if (caught != null) {
76      Object listener = provision.erredListener != null ?
77          provision.erredListener.getClass() : "(unknown)";
78      throw errors
79          .errorInUserCode(caught, "Error notifying ProvisionListener %s of %s.%n"
80              + " Reason: %s", listener, binding.getKey(), caught)
81          .toException();
82    } else {
83      return provision.result;
84    }
85  }
86
87  // TODO(sameb): Can this be more InternalFactory-like?
88  public interface ProvisionCallback<T> {
89    public T call() throws ErrorsException;
90  }
91
92  private class Provision extends ProvisionListener.ProvisionInvocation<T> {
93
94    final Errors errors;
95    final int numErrorsBefore;
96    final InternalContext context;
97    final ProvisionCallback<T> callable;
98    int index = -1;
99    T result;
100    ErrorsException exceptionDuringProvision;
101    ProvisionListener erredListener;
102
103    public Provision(Errors errors, InternalContext context, ProvisionCallback<T> callable) {
104      this.callable = callable;
105      this.context = context;
106      this.errors = errors;
107      this.numErrorsBefore = errors.size();
108    }
109
110    @Override
111    public T provision() {
112      index++;
113      if (index == listeners.length) {
114        try {
115          result = callable.call();
116          // Make sure we don't return the provisioned object if there were any errors
117          // injecting its field/method dependencies.
118          errors.throwIfNewErrors(numErrorsBefore);
119        } catch(ErrorsException ee) {
120          exceptionDuringProvision = ee;
121          throw new ProvisionException(errors.merge(ee.getErrors()).getMessages());
122        }
123      } else if (index < listeners.length) {
124        int currentIdx = index;
125        try {
126          listeners[index].onProvision(this);
127        } catch(RuntimeException re) {
128          erredListener = listeners[currentIdx];
129          throw re;
130        }
131        if (currentIdx == index) {
132          // Our listener didn't provision -- do it for them.
133          provision();
134        }
135      } else {
136        throw new IllegalStateException("Already provisioned in this listener.");
137      }
138      return result;
139    }
140
141    @Override
142    public Binding<T> getBinding() {
143      // TODO(sameb): Because so many places cast directly to BindingImpl & subclasses,
144      // we can't decorate this to prevent calling getProvider().get(), which means
145      // if someone calls that they'll get strange errors.
146      return binding;
147    }
148
149    @Override
150    public List<DependencyAndSource> getDependencyChain() {
151      return context.getDependencyChain();
152    }
153  }
154}
155