/*

  * Copyright 2007-2008 The Kuali Foundation

  *

  * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php

  *

  * 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.kuali.rice.core.util;

 import java.lang.ref.SoftReference;

 /**

  * An extension to SoftReference that stores an expiration time for the 

  * value stored in the SoftReference. If no expiration time is passed in

  * the value will never be cached.  

  */

 public class MaxAgeSoftReference<T> extends SoftReference<T> {

         private long expires;

         public MaxAgeSoftReference(long expires, T referent) {

                 super(referent);

                 this.expires = System.currentTimeMillis() + expires * 1000;

         }

         public boolean isValid() {

                 return System.currentTimeMillis() < expires;

         }

         public T get() {                        

                 return isValid() ? super.get() : null;

         }               

 }