Struts example source code file (FinalizableReferenceQueue.java)

This example Struts source code file (FinalizableReferenceQueue.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

error, finalizablereference, finalizablereference, finalizablereferencequeue, finalizablereferencequeue, interruptedexception, log, logger, logging, override, referencequeue, referencequeue, thread, thread, throwable

The Struts FinalizableReferenceQueue.java source code

/**
 * Copyright (C) 2006 Google Inc.
 *
 * 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 com.opensymphony.xwork2.inject.util;

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Starts a background thread that cleans up after reclaimed referents.
 *
 * @author Bob Lee (crazybob@google.com)
 */
class FinalizableReferenceQueue extends ReferenceQueue<Object> {

  private static final Logger logger =
      Logger.getLogger(FinalizableReferenceQueue.class.getName());

  private FinalizableReferenceQueue() {}

  void cleanUp(Reference reference) {
    try {
      ((FinalizableReference) reference).finalizeReferent();
    } catch (Throwable t) {
      deliverBadNews(t);
    }
  }

  void deliverBadNews(Throwable t) {
    logger.log(Level.SEVERE, "Error cleaning up after reference.", t);
  }

  void start() {
    Thread thread = new Thread("FinalizableReferenceQueue") {
      @Override
      public void run() {
        while (true) {
          try {
            cleanUp(remove());
          } catch (InterruptedException e) { /* ignore */ }
        }
      }
    };
    thread.setDaemon(true);
    thread.start();
  }

  static ReferenceQueue<Object> instance = createAndStart();

  static FinalizableReferenceQueue createAndStart() {
    FinalizableReferenceQueue queue = new FinalizableReferenceQueue();
    queue.start();
    return queue;
  }

  /**
   * Gets instance.
   */
  public static ReferenceQueue<Object> getInstance() {
    return instance;
  }
}