package org.codehaus.plexus;
   
   /*
    * Copyright 2001-2009 Codehaus Foundation.
    *
    * 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.
   */
  
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.LinkedHashSet;
  import java.util.LinkedList;
  import java.util.Queue;
  import java.util.Set;
  
  import org.codehaus.plexus.classworlds.ClassWorld;
  import org.codehaus.plexus.classworlds.realm.ClassRealm;
  
  public class ClassRealmUtil {
  
      public static Set<ClassRealm> getContextRealms(ClassWorld world) {
          Set<ClassRealm> realms = new LinkedHashSet<ClassRealm>();
  
          for (ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
                  classLoader != null;
                  classLoader = classLoader.getParent()) {
              if (classLoader instanceof ClassRealm) {
                  realms.add((ClassRealm) classLoader);
  
                  Queue<ClassRealm> queue = new LinkedList<ClassRealm>();
                  queue.add((ClassRealm) classLoader);
  
                  while (!queue.isEmpty()) {
                      ClassRealm realm = queue.remove();
  
                      Collection<ClassRealm> importRealms = realm.getImportRealms();
                      for (ClassRealm importRealm : importRealms) {
                          if (realms.add(importRealm)) {
                              queue.add(importRealm);
                          }
                      }
  
                      ClassRealm parentRealm = realm.getParentRealm();
                      if (parentRealm != null && realms.add(parentRealm)) {
                          queue.add(parentRealm);
                      }
                  }
              }
          }
  
          if (world != null) {
              for (Iterator<ClassRealm> it = realms.iterator(); it.hasNext(); ) {
                  ClassRealm realm = it.next();
                  if (realm.getWorld() != world) {
                      it.remove();
                  }
              }
          }
  
          return realms;
      }
  }