/**
* Copyright (C) 2006 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.opensymphony.xwork2.inject;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;
/**
* Context of a dependency construction. Used to manage circular references.
*
* @author [email protected] (Bob Lee)
*/
class ConstructionContext<T> {
T currentReference;
boolean constructing;
List<DelegatingInvocationHandler<T>> invocationHandlers;
T getCurrentReference() {
return currentReference;
}
void removeCurrentReference() {
this.currentReference = null;
}
void setCurrentReference(T currentReference) {
this.currentReference = currentReference;
}
boolean isConstructing() {
return constructing;
}
void startConstruction() {
this.constructing = true;
}
void finishConstruction() {
this.constructing = false;
invocationHandlers = null;
}
Object createProxy(Class<? super T> expectedType) {
// TODO: if I create a proxy which implements all the interfaces of
// the implementation type, I'll be able to get away with one proxy
// instance (as opposed to one per caller).
if (!expectedType.isInterface()) {
throw new DependencyException(
expectedType.getName() + " is not an interface.");
}
if (invocationHandlers == null) {
invocationHandlers = new ArrayList<DelegatingInvocationHandler<T>>();
}
DelegatingInvocationHandler<T> invocationHandler =
new DelegatingInvocationHandler<T>();
invocationHandlers.add(invocationHandler);
return Proxy.newProxyInstance(
expectedType.getClassLoader(),
new Class[] { expectedType },
invocationHandler
);
}
void setProxyDelegates(T delegate) {
if (invocationHandlers != null) {
for (DelegatingInvocationHandler<T> invocationHandler
: invocationHandlers) {
invocationHandler.setDelegate(delegate);
}
}
}
static class DelegatingInvocationHandler<T> implements InvocationHandler {
T delegate;
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
if (delegate == null) {
throw new IllegalStateException(
"Not finished constructing. Please don't call methods on this"
+ " object until the caller's construction is complete.");
}
try {
return method.invoke(delegate, args);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (IllegalArgumentException e) {
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
void setDelegate(T delegate) {
this.delegate = delegate;
}
}
}
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