如何从.jar加载文件夹？

好.所以我有一个非常简单的问题：我希望能够从正在运行的.jar文件中加载资源(整个文件夹),但我无法让它工作.这是我尝试过的(如果类名是“myClass”,文件夹被称为“myFolder”),但它总是抛出NullPointerException：

URL folderURL = myClass.class.getClassLoader().getResource("myFolder/");
String folderPath = folderURL.getPath();
File myFolder = new File(folderPath);

在创建“myFolder”之前,总是抛出NullPointerException.

更多信息：我必须从静态上下文访问该文件夹.正在访问该文件夹的类与文件夹本身所在的目录不在同一目录中.(该文件夹位于jar内的根目录中,该类是几个子包.)

有没有人能解决我的问题？对不起,如果我使用了错误的术语：P,但您可以做任何事情来帮助我们.

解决方法

如果你需要“暴力破解”由getResource(..)给出的URL指向的JAR目录中的子文件,请使用以下内容(尽管这有点像黑客！).它也适用于普通的文件系统：

/**
   * List directory contents for a resource folder. Not recursive.
   * This is basically a brute-force implementation.
   * Works for regular files and also JARs.
   * 
   * @author Greg Briggs
   * @param clazz Any java class that lives in the same place as the resources you want.
   * @param path Should end with "/",but not start with one.
   * @return Just the name of each member item,not the full paths.
   * @throws URISyntaxException 
   * @throws IOException 
   */
  String[] getResourceListing(Class clazz,String path) throws URISyntaxException,IOException {
      URL dirURL = clazz.getClassLoader().getResource(path);
      if (dirURL != null && dirURL.getProtocol().equals("file")) {
        /* A file path: easy enough */
        return new File(dirURL.toURI()).list();
      } 

      if (dirURL == null) {
        /* 
         * In case of a jar file,we can't actually find a directory.
         * Have to assume the same jar as clazz.
         */
        String me = clazz.getName().replace(".","/")+".class";
        dirURL = clazz.getClassLoader().getResource(me);
      }

      if (dirURL.getProtocol().equals("jar")) {
        /* A JAR path */
        String jarPath = dirURL.getPath().substring(5,dirURL.getPath().indexOf("!")); //strip out only the JAR file
        JarFile jar = new JarFile(URLDecoder.decode(jarPath,"UTF-8"));
        Enumeration<JarEntry> entries = jar.entries(); //gives ALL entries in jar
        Set<String> result = new HashSet<String>(); //avoid duplicates in case it is a subdirectory
        while(entries.hasMoreElements()) {
          String name = entries.nextElement().getName();
          if (name.startsWith(path)) { //filter according to the path
            String entry = name.substring(path.length());
            int checkSubdir = entry.indexOf("/");
            if (checkSubdir >= 0) {
              // if it is a subdirectory,we just return the directory name
              entry = entry.substring(0,checkSubdir);
            }
            result.add(entry);
          }
        }
        return result.toArray(new String[result.size()]);
      } 

      throw new UnsupportedOperationException("Cannot list files for URL "+dirURL);
  }

然后,您可以修改getResource(..)给出的URL并将文件附加到末尾,并将这些URL传递给getResourceAsStream(..),以备加载.如果您不理解这一点,则需要阅读类加载.

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