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The Apache Commons Collections package contains types that extend and augment the Java Collections Framework.
/*
* 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.collections4.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.collections4.Factory;
import org.apache.commons.collections4.FunctorException;
/**
* Factory implementation that creates a new instance each time based on a prototype.
*
* WARNING: from v4.1 onwards {@link Factory} instances returned by
* {@link #prototypeFactory(Object)} will not be serializable anymore in order
* to prevent potential remote code execution exploits. Please refer to
* COLLECTIONS-580
* for more details.
*
* @since 3.0
*/
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 the type the factory creates
* @param prototype the object to clone each time in the factory
* @return the prototype factory, or a {@link ConstantFactory#NULL_INSTANCE} if
* the {@code prototype} is {@code null}
* @throws IllegalArgumentException if the prototype cannot be cloned
*/
@SuppressWarnings("unchecked")
public static Factory prototypeFactory(final T prototype) {
if (prototype == null) {
return ConstantFactory.constantFactory(null);
}
try {
final Method method = prototype.getClass().getMethod("clone", (Class[]) null);
return new PrototypeCloneFactory<>(prototype, method);
} catch (final NoSuchMethodException ex) {
try {
prototype.getClass().getConstructor(new Class[] { prototype.getClass() });
return new InstantiateFactory<>(
(Class) prototype.getClass(),
new Class[] { prototype.getClass() },
new Object[] { prototype });
} catch (final NoSuchMethodException ex2) {
if (prototype instanceof Serializable) {
return (Factory) new PrototypeSerializationFactory<>((Serializable) prototype);
}
}
}
throw new IllegalArgumentException("The prototype must be cloneable via a public clone method");
}
/**
* Restricted constructor.
*/
private PrototypeFactory() {
super();
}
// PrototypeCloneFactory
//-----------------------------------------------------------------------
/**
* PrototypeCloneFactory creates objects by copying a prototype using the clone method.
*/
static class PrototypeCloneFactory implements Factory {
/** The object to clone each time */
private final T iPrototype;
/** The method used to clone */
private transient Method iCloneMethod;
/**
* Constructor to store prototype.
*/
private PrototypeCloneFactory(final T prototype, final 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 (final 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
*/
@Override
@SuppressWarnings("unchecked")
public T create() {
// needed for post-serialization
if (iCloneMethod == null) {
findCloneMethod();
}
try {
return (T) iCloneMethod.invoke(iPrototype, (Object[]) null);
} catch (final IllegalAccessException ex) {
throw new FunctorException("PrototypeCloneFactory: Clone method must be public", ex);
} catch (final 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 {
/** The object to clone via serialization each time */
private final T iPrototype;
/**
* Constructor to store prototype
*/
private PrototypeSerializationFactory(final T prototype) {
super();
iPrototype = prototype;
}
/**
* Creates an object using serialization.
*
* @return the new object
*/
@Override
@SuppressWarnings("unchecked")
public T create() {
final ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
ByteArrayInputStream bais = null;
try {
final ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(iPrototype);
bais = new ByteArrayInputStream(baos.toByteArray());
final ObjectInputStream in = new ObjectInputStream(bais);
return (T) in.readObject();
} catch (final ClassNotFoundException ex) {
throw new FunctorException(ex);
} catch (final IOException ex) {
throw new FunctorException(ex);
} finally {
try {
if (bais != null) {
bais.close();
}
} catch (final IOException ex) { //NOPMD
// ignore
}
try {
baos.close();
} catch (final IOException ex) { //NOPMD
// ignore
}
}
}
}
}