org.apache.commons.collections.functors.PrototypeFactory Maven / Gradle / Ivy
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* 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.
*/
package org.apache.commons.collections.functors;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import org.apache.commons.collections.Factory;
import org.apache.commons.collections.FunctorException;
/**
* Factory implementation that creates a new instance each time based on a prototype.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public class PrototypeFactory {
/**
* Factory method that performs validation.
*
* Creates a Factory that will return a clone of the same prototype object
* each time the factory is used. The prototype will be cloned using one of these
* techniques (in order):
*
* - public clone method
*
- public copy constructor
*
- serialization clone
*
*
* @param prototype the object to clone each time in the factory
* @return the prototype factory
* @throws IllegalArgumentException if the prototype is null
* @throws IllegalArgumentException if the prototype cannot be cloned
*/
public static Factory getInstance(Object prototype) {
if (prototype == null) {
return ConstantFactory.NULL_INSTANCE;
}
try {
Method method = prototype.getClass().getMethod("clone", (Class[]) null);
return new PrototypeCloneFactory(prototype, method);
} catch (NoSuchMethodException ex) {
try {
prototype.getClass().getConstructor(new Class[] { prototype.getClass()});
return new InstantiateFactory(
prototype.getClass(),
new Class[] { prototype.getClass()},
new Object[] { prototype });
} catch (NoSuchMethodException ex2) {
if (prototype instanceof Serializable) {
return new PrototypeSerializationFactory((Serializable) prototype);
}
}
}
throw new IllegalArgumentException("The prototype must be cloneable via a public clone method");
}
/**
* Constructor that performs no validation.
* Use getInstance if you want that.
*/
private PrototypeFactory() {
super();
}
// PrototypeCloneFactory
//-----------------------------------------------------------------------
/**
* PrototypeCloneFactory creates objects by copying a prototype using the clone method.
*/
static class PrototypeCloneFactory implements Factory, Serializable {
/** The serial version */
private static final long serialVersionUID = 5604271422565175555L;
/** The object to clone each time */
private final Object iPrototype;
/** The method used to clone */
private transient Method iCloneMethod;
/**
* Constructor to store prototype.
*/
private PrototypeCloneFactory(Object prototype, Method method) {
super();
iPrototype = prototype;
iCloneMethod = method;
}
/**
* Find the Clone method for the class specified.
*/
private void findCloneMethod() {
try {
iCloneMethod = iPrototype.getClass().getMethod("clone", (Class[]) null);
} catch (NoSuchMethodException ex) {
throw new IllegalArgumentException("PrototypeCloneFactory: The clone method must exist and be public ");
}
}
/**
* Creates an object by calling the clone method.
*
* @return the new object
*/
public Object create() {
// needed for post-serialization
if (iCloneMethod == null) {
findCloneMethod();
}
try {
return iCloneMethod.invoke(iPrototype, (Object[])null);
} catch (IllegalAccessException ex) {
throw new FunctorException("PrototypeCloneFactory: Clone method must be public", ex);
} catch (InvocationTargetException ex) {
throw new FunctorException("PrototypeCloneFactory: Clone method threw an exception", ex);
}
}
}
// PrototypeSerializationFactory
//-----------------------------------------------------------------------
/**
* PrototypeSerializationFactory creates objects by cloning a prototype using serialization.
*/
static class PrototypeSerializationFactory implements Factory, Serializable {
/** The serial version */
private static final long serialVersionUID = -8704966966139178833L;
/** The object to clone via serialization each time */
private final Serializable iPrototype;
/**
* Constructor to store prototype
*/
private PrototypeSerializationFactory(Serializable prototype) {
super();
iPrototype = prototype;
}
/**
* Creates an object using serialization.
*
* @return the new object
*/
public Object create() {
ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
ByteArrayInputStream bais = null;
try {
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(iPrototype);
bais = new ByteArrayInputStream(baos.toByteArray());
ObjectInputStream in = new ObjectInputStream(bais);
return in.readObject();
} catch (ClassNotFoundException ex) {
throw new FunctorException(ex);
} catch (IOException ex) {
throw new FunctorException(ex);
} finally {
try {
if (bais != null) {
bais.close();
}
} catch (IOException ex) {
// ignore
}
try {
if (baos != null) {
baos.close();
}
} catch (IOException ex) {
// ignore
}
}
}
}
}