net.ftlines.wicket.validation.bean.ClassReference.java Source code

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Here is the source code for net.ftlines.wicket.validation.bean.ClassReference.java

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/**
 * 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.
 */

package net.ftlines.wicket.validation.bean;

import java.io.Serializable;
import java.lang.ref.WeakReference;

import org.apache.wicket.Application;

/**
 * A serialization-safe reference to a {@link Class}
 * 
 * @author igor
 * 
 * @param <T>
 *            type of class
 */
public class ClassReference<T> implements Serializable {
    private transient WeakReference<Class<? extends T>> cache;
    private final String name;

    /**
     * Constructor
     * 
     * @param clazz
     */
    public ClassReference(Class<? extends T> clazz) {
        name = clazz.getName();
        cache(clazz);
    }

    /**
     * Gets the {@link Class} stored in this reference
     * 
     * @return
     */
    @SuppressWarnings("unchecked")
    public Class<? extends T> get() {
        Class<? extends T> clazz = cache != null ? cache.get() : null;
        if (clazz == null) {
            try {
                clazz = (Class<? extends T>) Application.get().getApplicationSettings().getClassResolver()
                        .resolveClass(name);
            } catch (ClassNotFoundException e) {
                throw new RuntimeException("Could not resolve class: " + name, e);
            }
            cache(clazz);
        }
        return clazz;
    }

    private void cache(Class<? extends T> clazz) {
        cache = new WeakReference<Class<? extends T>>(clazz);
    }

    /**
     * Diamond operator factory
     * 
     * @param <T>
     * @param clazz
     * @return
     */
    public static <T> ClassReference<T> of(Class<T> clazz) {
        return new ClassReference<T>(clazz);
    }
}