com.jianggujin.modulelink.util.vfs.JJBoss6VFS Maven / Gradle / Ivy

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/**
 * Copyright 2018 jianggujin (www.jianggujin.com).
 * 
 * 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.jianggujin.modulelink.util.vfs;

import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * 一个用于JBoss6的{@link JVFS }实现
 * 
 * @author jianggujin
 *
 */
public class JJBoss6VFS extends JVFS {

   /**
    * 模仿JBoss VirtualFile类的精简实现
    * 
    * @author jianggujin
    *
    */
   static class VirtualFile {
      static Class VirtualFile;
      static Method getPathNameRelativeTo, getChildrenRecursively;

      Object virtualFile;

      VirtualFile(Object virtualFile) {
         this.virtualFile = virtualFile;
      }

      String getPathNameRelativeTo(VirtualFile parent) {
         try {
            return invoke(getPathNameRelativeTo, virtualFile, parent.virtualFile);
         } catch (IOException e) {
            return null;
         }
      }

      List getChildren() throws IOException {
         List objects = invoke(getChildrenRecursively, virtualFile);
         List children = new ArrayList(objects.size());
         for (Object object : objects) {
            children.add(new VirtualFile(object));
         }
         return children;
      }
   }

   /**
    * 模仿JBoss VFS类的精简实现
    * 
    * @author jianggujin
    *
    */
   static class VFS {
      static Class VFS;
      static Method getChild;

      private VFS() {
      }

      static VirtualFile getChild(URL url) throws IOException {
         Object o = invoke(getChild, VFS, url);
         return o == null ? null : new VirtualFile(o);
      }
   }

   /**
    * 表示VFS当前的环境是否有效
    */
   private static Boolean valid;

   /**
    * 找到所有需要访问JBoss 6 VFS的类和方法
    */
   protected static synchronized void initialize() {
      if (valid == null) {
         // 假设有效。如果出错，它会被翻转
         valid = Boolean.TRUE;

         // 查找和验证所需的类
         VFS.VFS = checkNotNull(getClass("org.jboss.vfs.VFS"));
         VirtualFile.VirtualFile = checkNotNull(getClass("org.jboss.vfs.VirtualFile"));

         // 查找和验证所需的方法
         VFS.getChild = checkNotNull(getMethod(VFS.VFS, "getChild", URL.class));
         VirtualFile.getChildrenRecursively = checkNotNull(
               getMethod(VirtualFile.VirtualFile, "getChildrenRecursively"));
         VirtualFile.getPathNameRelativeTo = checkNotNull(
               getMethod(VirtualFile.VirtualFile, "getPathNameRelativeTo", VirtualFile.VirtualFile));

         // 验证API没有改变
         checkReturnType(VFS.getChild, VirtualFile.VirtualFile);
         checkReturnType(VirtualFile.getChildrenRecursively, List.class);
         checkReturnType(VirtualFile.getPathNameRelativeTo, String.class);
      }
   }

   /**
    * 验证所提供的对象引用是否为null。如果它是空的，那么VFS在当前环境终将被标记为无效
    * 
    * @param object
    * @return
    */
   protected static  T checkNotNull(T object) {
      if (object == null) {
         setInvalid();
      }
      return object;
   }

   /**
    * 验证方法的返回类型是期望的类型。如果不是，那么VFS在当前环境终将被标记为无效
    * 
    * @param method
    * @param expected
    */
   protected static void checkReturnType(Method method, Class expected) {
      if (method != null && !expected.isAssignableFrom(method.getReturnType())) {
         setInvalid();
      }
   }

   /**
    * 标记VFS在当前环境是无效的
    */
   protected static void setInvalid() {
      if (JJBoss6VFS.valid == Boolean.TRUE) {
         JJBoss6VFS.valid = Boolean.FALSE;
      }
   }

   static {
      initialize();
   }

   @Override
   public boolean isValid() {
      return valid;
   }

   @Override
   public List list(URL url, String path) throws IOException {
      VirtualFile directory;
      directory = VFS.getChild(url);
      if (directory == null) {
         return Collections.emptyList();
      }

      if (!path.endsWith("/")) {
         path += "/";
      }

      List children = directory.getChildren();
      List names = new ArrayList(children.size());
      for (VirtualFile vf : children) {
         names.add(path + vf.getPathNameRelativeTo(directory));
      }

      return names;
   }
}