/**
    * Copyright 2005-2012 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.ksb.util;
  
  import org.apache.log4j.Logger;
  import org.apache.xml.security.algorithms.SignatureAlgorithm;
  import org.kuali.rice.core.framework.util.ApplicationThreadLocal;
  import org.springframework.beans.BeansException;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextAware;
  import org.springframework.context.ApplicationListener;
  import org.springframework.context.ConfigurableApplicationContext;
  import org.springframework.context.event.ContextClosedEvent;
  
  import java.lang.reflect.Field;
  import java.util.ArrayList;
  import java.util.Collection;
  
  /**
   * Removes {@link SignatureAlgorithm} ThreadLocals
   */
  public class SignatureAlgorithmCacheCleaner implements ApplicationContextAware {
      private static final Logger LOG = Logger.getLogger(SignatureAlgorithmCacheCleaner.class);
  
      /**
       * Registers a listener that removes SignatureAlgorithm key caches on context shutdown
       * @param applicationContext spring context
       */
      @Override
      public void setApplicationContext(ApplicationContext applicationContext) {
          // register a context close handler
          if (applicationContext instanceof ConfigurableApplicationContext) {
              ConfigurableApplicationContext context = (ConfigurableApplicationContext) applicationContext;
              context.addApplicationListener(new ApplicationListener<ContextClosedEvent>() {
                  @Override
                  public synchronized void onApplicationEvent(ContextClosedEvent e) {
                      LOG.info("Context '" + e.getApplicationContext().getDisplayName() + "' closed, removing SignatureAlgorithm caches");
  
                      // obtain the thread local caches via reflection
                      String[] threadLocalFields = new String[] { "instancesSigning", "instancesVerify", "keysSigning", "keysVerify" };
                      Collection<ThreadLocal> threadLocals = new ArrayList<ThreadLocal>(threadLocalFields.length);
                      for (String fname: threadLocalFields) {
                          try {
                              Field f = SignatureAlgorithm.class.getDeclaredField(fname);
                              if (f != null) {
                                  f.setAccessible(true);
                                  ThreadLocal tl = (ThreadLocal) f.get(null);
                                  if (tl != null) {
                                      threadLocals.add(tl);
                                  }
                              }
                          } catch (NoSuchFieldException nsme) {
                              nsme.printStackTrace();
                          } catch (IllegalAccessException iae) {
                              iae.printStackTrace();
                          }
                      }
  
                      // remove the thread locals from every thread
                      if (!threadLocals.isEmpty()) {
                          for (Thread t: Thread.getAllStackTraces().keySet()) {
                              for (ThreadLocal tl: threadLocals) {
                                  ApplicationThreadLocal.removeThreadLocal(t, tl);
                              }
                          }
                      }
                  }
              });
          }
      }
  }