package org.apache.ojb.broker.util;
/* Copyright 2003-2004 The Apache Software Foundation
*
* 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.
*/
import java.lang.reflect.Constructor;
import org.apache.ojb.broker.metadata.ClassNotPersistenceCapableException;
/**
* This class helps us to construct new instances.
* We don't want to rely on public default constructors and
* have to try hard to also use private or protected constructors.
*
* @author Thomas Mahler
* @author Lance Eason
*
* @version $Id: ConstructorHelper.java,v 1.7 2004/05/03 23:05:56 arminw Exp $
*/
public class ConstructorHelper
{
/**
* represents a zero sized parameter array
*/
private static final Object[] NO_ARGS = {};
/**
* no public constructor, please use the static method only.
*/
private ConstructorHelper()
{
}
/**
* create a new instance of class clazz.
* first use the public default constructor.
* If this fails also try to use protected an private constructors.
* @param clazz the class to instantiate
* @return the fresh instance of class clazz
* @throws InstantiationException
*/
public static Object instantiate(Class clazz) throws InstantiationException
{
Object result = null;
try
{
result = ClassHelper.newInstance(clazz);
}
catch(IllegalAccessException e)
{
try
{
result = ClassHelper.newInstance(clazz, true);
}
catch(Exception e1)
{
throw new ClassNotPersistenceCapableException("Can't instantiate class '"
+ (clazz != null ? clazz.getName() : "null")
+ "', message was: " + e1.getMessage() + ")", e1);
}
}
return result;
}
/**
* create a new instance of the class represented by the no-argument constructor provided
* @param constructor the zero argument constructor for the class
* @return a new instance of the class
* @throws InstantiationException
* @throws ClassNotPersistenceCapableException if the constructor is null or there is an
* exception while trying to create a new instance
*/
public static Object instantiate(Constructor constructor) throws InstantiationException
{
if(constructor == null)
{
throw new ClassNotPersistenceCapableException(
"A zero argument constructor was not provided!");
}
Object result = null;
try
{
result = constructor.newInstance(NO_ARGS);
}
catch(InstantiationException e)
{
throw e;
}
catch(Exception e)
{
throw new ClassNotPersistenceCapableException("Can't instantiate class '"
+ (constructor != null ? constructor.getDeclaringClass().getName() : "null")
+ "' with given constructor: " + e.getMessage(), e);
}
return result;
}
}