一、前言

关于apache的fediz-core源码包中的org.apache.cxf.fediz.core.util.ClassLoaderUtils类加载器工具类，通过URLClassLoader加载URL链接加载资源getURLClassLoader、获取getResources类的URL资源集及加载loadClass自定类资源等。

二、源码说明

package org.apache.cxf.fediz.core.util;@b@@b@import java.io.IOException;@b@import java.io.InputStream;@b@import java.net.URL;@b@import java.net.URLClassLoader;@b@import java.security.AccessController;@b@import java.security.PrivilegedAction;@b@import java.util.ArrayList;@b@import java.util.Enumeration;@b@import java.util.List;@b@@b@public final class ClassLoaderUtils@b@{@b@  public static ClassLoaderHolder setThreadContextClassloader(ClassLoader newLoader)@b@  {@b@    return ((ClassLoaderHolder)AccessController.doPrivileged(new PrivilegedAction(newLoader) {@b@      public ClassLoaderUtils.ClassLoaderHolder run() {@b@        ClassLoader l = Thread.currentThread().getContextClassLoader();@b@        Thread.currentThread().setContextClassLoader(this.val$newLoader);@b@        return new ClassLoaderUtils.ClassLoaderHolder(l);@b@      }@b@    }));@b@  }@b@@b@  public static ClassLoader getURLClassLoader(URL[] urls, ClassLoader parent)@b@  {@b@    return ((ClassLoader)AccessController.doPrivileged(new PrivilegedAction(urls, parent) {@b@      public ClassLoader run() {@b@        return new URLClassLoader(this.val$urls, this.val$parent);@b@      }@b@    }));@b@  }@b@@b@  public static ClassLoader getURLClassLoader(List<URL> urlList, ClassLoader parent)@b@  {@b@    return getURLClassLoader((URL[])urlList.toArray(new URL[urlList.size()]), parent);@b@  }@b@@b@  public static URL getResource(String resourceName, Class<?> callingClass)@b@  {@b@    URL url = Thread.currentThread().getContextClassLoader().getResource(resourceName);@b@    if ((url == null) && (resourceName.startsWith("/")))@b@    {@b@      url = Thread.currentThread().getContextClassLoader().getResource(resourceName.substring(1));@b@    }@b@@b@    ClassLoader cluClassloader = ClassLoaderUtils.class.getClassLoader();@b@    if (cluClassloader == null)@b@      cluClassloader = ClassLoader.getSystemClassLoader();@b@@b@    if (url == null)@b@      url = cluClassloader.getResource(resourceName);@b@@b@    if ((url == null) && (resourceName.startsWith("/")))@b@    {@b@      url = cluClassloader.getResource(resourceName.substring(1));@b@    }@b@@b@    if (url == null) {@b@      ClassLoader cl = callingClass.getClassLoader();@b@@b@      if (cl != null)@b@        url = cl.getResource(resourceName);@b@@b@    }@b@@b@    if (url == null) {@b@      url = callingClass.getResource(resourceName);@b@    }@b@@b@    if ((url == null) && (resourceName != null) && (resourceName.charAt(0) != '/')) {@b@      return getResource('/' + resourceName, callingClass);@b@    }@b@@b@    return url;@b@  }@b@@b@  public static List<URL> getResources(String resourceName, Class<?> callingClass)@b@  {@b@    List ret = new ArrayList();@b@    Enumeration urls = new Enumeration() {@b@      public boolean hasMoreElements() {@b@        return false; }@b@@b@      public URL nextElement() {@b@        return null;@b@      }@b@    };@b@    try@b@    {@b@      urls = Thread.currentThread().getContextClassLoader().getResources(resourceName);@b@    }@b@    catch (IOException e)@b@    {@b@    }@b@    if ((!(urls.hasMoreElements())) && (resourceName.startsWith("/")))@b@      try@b@      {@b@        urls = Thread.currentThread().getContextClassLoader().getResources(resourceName.substring(1));@b@      }@b@      catch (IOException e)@b@      {@b@      }@b@@b@@b@    ClassLoader cluClassloader = ClassLoaderUtils.class.getClassLoader();@b@    if (cluClassloader == null)@b@      cluClassloader = ClassLoader.getSystemClassLoader();@b@@b@    if (!(urls.hasMoreElements()))@b@      try {@b@        urls = cluClassloader.getResources(resourceName);@b@      }@b@      catch (IOException e)@b@      {@b@      }@b@    if ((!(urls.hasMoreElements())) && (resourceName.startsWith("/")))@b@      try@b@      {@b@        urls = cluClassloader.getResources(resourceName.substring(1));@b@      }@b@      catch (IOException e)@b@      {@b@      }@b@@b@    if (!(urls.hasMoreElements())) {@b@      ClassLoader cl = callingClass.getClassLoader();@b@@b@      if (cl != null)@b@        try {@b@          urls = cl.getResources(resourceName);@b@        }@b@        catch (IOException e)@b@        {@b@        }@b@    }@b@@b@    if (!(urls.hasMoreElements())) {@b@      URL url = callingClass.getResource(resourceName);@b@      if (url != null)@b@        ret.add(url);@b@    }@b@@b@    while (urls.hasMoreElements()) {@b@      ret.add(urls.nextElement());@b@    }@b@@b@    if ((ret.isEmpty()) && (resourceName != null) && (resourceName.charAt(0) != '/'))@b@      return getResources('/' + resourceName, callingClass);@b@@b@    return ret;@b@  }@b@@b@  public static InputStream getResourceAsStream(String resourceName, Class<?> callingClass)@b@  {@b@    URL url = getResource(resourceName, callingClass);@b@    try@b@    {@b@      return ((url != null) ? url.openStream() : null); } catch (IOException e) {@b@    }@b@    return null;@b@  }@b@@b@  public static Class<?> loadClass(String className, Class<?> callingClass)@b@    throws ClassNotFoundException@b@  {@b@    ClassLoader cl;@b@    try@b@    {@b@      cl = Thread.currentThread().getContextClassLoader();@b@@b@      if (cl != null)@b@        return cl.loadClass(className);@b@    }@b@    catch (ClassNotFoundException e)@b@    {@b@    }@b@    return loadClass2(className, callingClass); }@b@@b@  public static <T> Class<? extends T> loadClass(String className, Class<?> callingClass, Class<T> type) throws ClassNotFoundException {@b@    ClassLoader cl;@b@    try {@b@      cl = Thread.currentThread().getContextClassLoader();@b@@b@      if (cl != null)@b@        return cl.loadClass(className).asSubclass(type);@b@    }@b@    catch (ClassNotFoundException e)@b@    {@b@    }@b@    return loadClass2(className, callingClass).asSubclass(type);@b@  }@b@@b@  private static Class<?> loadClass2(String className, Class<?> callingClass) throws ClassNotFoundException {@b@    try {@b@      return Class.forName(className);@b@    } catch (ClassNotFoundException ex) {@b@      try {@b@        if (ClassLoaderUtils.class.getClassLoader() != null)@b@          return ClassLoaderUtils.class.getClassLoader().loadClass(className);@b@      }@b@      catch (ClassNotFoundException exc) {@b@        if ((callingClass != null) && (callingClass.getClassLoader() != null))@b@          return callingClass.getClassLoader().loadClass(className);@b@      }@b@@b@      throw ex;@b@    }@b@  }@b@@b@  public static class ClassLoaderHolder@b@  {@b@    ClassLoader loader;@b@@b@    ClassLoaderHolder(ClassLoader c)@b@    {@b@      this.loader = c;@b@    }@b@@b@    public void reset() {@b@      ClassLoaderUtils.setThreadContextClassloader(this.loader);@b@    }@b@  }@b@}