package org.apache.ddlutils.util;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import org.apache.commons.collections.Closure;
import org.apache.ddlutils.DdlUtilsException;
/**
* A closure that determines a callback for the type of the object and calls it.
* Note that inheritance is also taken into account. I.e. if the object is of
* type B which is a subtype of A, and there is only a callback for type A,
* then this one will be invoked. If there is however also a callback for type B,
* then only this callback for type B will be invoked and not the one for type A.
*
* @version $Revision: $
*/
public class CallbackClosure implements Closure
{
/** The object on which the callbacks will be invoked. */
private Object _callee;
/** The parameter types. */
private Class[] _parameterTypes;
/** The parameters. */
private Object[] _parameters;
/** The position of the callback parameter type. */
private int _callbackTypePos = -1;
/** The cached callbacks. */
private Map _callbacks = new HashMap();
/**
* Creates a new closure object.
*
* @param callee The object on which the callbacks will be invoked
* @param callbackName The name of the callback method
* @param parameterTypes The parameter types. This array has to contain one <code>null</code>
* for the type of the object for which the callback is invoked.
* <code>null</code> or an empty array is regarded to be the
* same as an array containing a single <code>null</code>
* @param parameters The actual arguments. The value at the placeholder position
* will be ignored. Can be <code>null</code> if no parameter types
* where given
*/
public CallbackClosure(Object callee, String callbackName, Class[] parameterTypes, Object[] parameters)
{
_callee = callee;
if ((parameterTypes == null) || (parameterTypes.length == 0))
{
_parameterTypes = new Class[] { null };
_parameters = new Object[] { null };
_callbackTypePos = 0;
}
else
{
_parameterTypes = new Class[parameterTypes.length];
_parameters = new Object[parameterTypes.length];
for (int idx = 0; idx < parameterTypes.length; idx++)
{
if (parameterTypes[idx] == null)
{
if (_callbackTypePos >= 0)
{
throw new IllegalArgumentException("The parameter types may contain null only once");
}
_callbackTypePos = idx;
}
else
{
_parameterTypes[idx] = parameterTypes[idx];
_parameters[idx] = parameters[idx];
}
}
if (_callbackTypePos < 0)
{
throw new IllegalArgumentException("The parameter types need to a null placeholder");
}
}
Class type = callee.getClass();
// we're caching the callbacks
do
{
Method[] methods = type.getDeclaredMethods();
if (methods != null)
{
for (int idx = 0; idx < methods.length; idx++)
{
Method method = methods[idx];
Class[] paramTypes = methods[idx].getParameterTypes();
method.setAccessible(true);
if (method.getName().equals(callbackName) && typesMatch(paramTypes))
{
if (_callbacks.get(paramTypes[_callbackTypePos]) == null)
{
_callbacks.put(paramTypes[_callbackTypePos], methods[idx]);
}
}
}
}
type = type.getSuperclass();
}
while ((type != null) && !type.equals(Object.class));
}
/**
* Checks whether the given method parameter types match the expected ones.
*
* @param methodParamTypes The method parameter types
* @return <code>true</code> if the parameter types match
*/
private boolean typesMatch(Class[] methodParamTypes)
{
if ((methodParamTypes == null) || (_parameterTypes.length != methodParamTypes.length))
{
return false;
}
for (int idx = 0; idx < _parameterTypes.length; idx++)
{
if ((idx != _callbackTypePos) && !_parameterTypes[idx].equals(methodParamTypes[idx]))
{
return false;
}
}
return true;
}
/**
* {@inheritDoc}
*/
public void execute(Object obj) throws DdlUtilsException
{
LinkedList queue = new LinkedList();
queue.add(obj.getClass());
while (!queue.isEmpty())
{
Class type = (Class)queue.removeFirst();
Method callback = (Method)_callbacks.get(type);
if (callback != null)
{
try
{
_parameters[_callbackTypePos] = obj;
callback.invoke(_callee, _parameters);
return;
}
catch (InvocationTargetException ex)
{
throw new DdlUtilsException(ex.getTargetException());
}
catch (IllegalAccessException ex)
{
throw new DdlUtilsException(ex);
}
}
if ((type.getSuperclass() != null) && !type.getSuperclass().equals(Object.class))
{
queue.add(type.getSuperclass());
}
Class[] baseInterfaces = type.getInterfaces();
if (baseInterfaces != null)
{
for (int idx = 0; idx < baseInterfaces.length; idx++)
{
queue.add(baseInterfaces[idx]);
}
}
}
}
}