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/**
* Copyright (C) 2011 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.inject.internal;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.inject.internal.ProvisionListenerStackCallback.ProvisionCallback;
import com.google.inject.spi.Dependency;
import javax.inject.Provider;
/**
* Base class for InternalFactories that are used by Providers, to handle
* circular dependencies.
*
* @author sameb@google.com (Sam Berlin)
*/
abstract class ProviderInternalFactory<T> implements InternalFactory<T> {
private final ProvisionListenerStackCallback<T> provisionCallback;
private final boolean allowProxy;
protected final Object source;
ProviderInternalFactory(Object source, boolean allowProxy,
ProvisionListenerStackCallback<T> provisionCallback) {
this.provisionCallback = checkNotNull(provisionCallback, "provisionCallback");
this.source = checkNotNull(source, "source");
this.allowProxy = allowProxy;
}
protected T circularGet(final Provider<? extends T> provider, final Errors errors,
InternalContext context, final Dependency<?> dependency, boolean linked)
throws ErrorsException {
Class<?> expectedType = dependency.getKey().getTypeLiteral().getRawType();
final ConstructionContext<T> constructionContext = context.getConstructionContext(this);
// We have a circular reference between constructors. Return a proxy.
if (constructionContext.isConstructing()) {
if (!allowProxy) {
throw errors.circularProxiesDisabled(expectedType).toException();
} else {
// TODO: if we can't proxy this object, can we proxy the other object?
@SuppressWarnings("unchecked")
T proxyType = (T) constructionContext.createProxy(errors, expectedType);
return proxyType;
}
}
// Optimization: Don't go through the callback stack if no one's listening.
if (!provisionCallback.hasListeners()) {
return provision(provider, errors, dependency, constructionContext);
} else {
return provisionCallback.provision(errors, context, new ProvisionCallback<T>() {
public T call() throws ErrorsException {
return provision(provider, errors, dependency, constructionContext);
}
});
}
}
/**
* Provisions a new instance. Subclasses should override this to catch
* exceptions & rethrow as ErrorsExceptions.
*/
protected T provision(Provider<? extends T> provider, Errors errors, Dependency<?> dependency,
ConstructionContext<T> constructionContext) throws ErrorsException {
constructionContext.startConstruction();
try {
T t = errors.checkForNull(provider.get(), source, dependency);
constructionContext.setProxyDelegates(t);
return t;
} finally {
constructionContext.finishConstruction();
}
}
}
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