/*
* 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.wicket.util.reference;
import java.io.Serializable;
import java.lang.ref.WeakReference;
import java.util.function.Supplier;
import org.apache.wicket.core.util.lang.WicketObjects;
/**
* A serialization-safe reference to a {@link Class}
*
* @author igor
*
* @param <T>
* type of class
*/
public class ClassReference<T> implements Serializable, Supplier<Class<T>>
{
private static final long serialVersionUID = 1L;
private transient WeakReference<Class<T>> cache;
private final String name;
/**
* Constructor
*
* @param clazz
* The referenced class
*/
public ClassReference(Class<T> clazz)
{
name = clazz.getName();
cache(clazz);
}
/**
* @return the {@link Class} stored in this reference
*/
public Class<T> get()
{
Class<T> clazz = cache != null ? cache.get() : null;
if (clazz == null)
{
clazz = WicketObjects.resolveClass(name);
if (clazz == null)
{
throw new RuntimeException("Could not resolve class: " + name);
}
cache(clazz);
}
return clazz;
}
private void cache(Class<T> clazz)
{
cache = new WeakReference<>(clazz);
}
/**
* Diamond operator factory
*
* @param clazz
* The referenced class
* @return class reference
*/
public static <T> ClassReference<T> of(Class<T> clazz)
{
return new ClassReference<>(clazz);
}
}