//文件复制解析，复制文件到cache　directory 中 ,VM options : -Dvertx.disableFileCPResolving

public static final String DISABLE_CP_RESOLVING_PROP_NAME = "vertx.disableFileCPResolving";

private static final boolean ENABLE_CP_RESOLVING = !Boolean.getBoolean(DISABLE_CP_RESOLVING_PROP_NAME);

/**

  * enableCaching 文件解析器是否用缓存，默认ture,

  * 设置两种方式:一、VertxOptions类的setFileResolverCachingEnabled方法

  *　二、设置system property,VM options "-Dvertx.disableFileCaching",对原代码无侵入性

  */

public FileResolver(Vertx vertx, boolean enableCaching) {

    this.vertx = vertx;

    this.enableCaching = enableCaching;

    //获取工作目录 -Dvertx.cwd

    String cwdOverride = System.getProperty("vertx.cwd");

    if (cwdOverride != null) {

      cwd = new File(cwdOverride).getAbsoluteFile();

    } else {

      cwd = null;

    }

    if (ENABLE_CP_RESOLVING) {

      setupCacheDir();

    }

}

/**

  *  建立cache目录

  */

private void setupCacheDir() {

　　//CACHE_DIR_BASE 通过-Dvertx.cacheDirBase设置，默认当前工作目录 .vertx隐藏目录下

    String cacheDirName = CACHE_DIR_BASE + "/file-cache-" + UUID.randomUUID().toString();

    cacheDir = new File(cacheDirName);

    if (!cacheDir.mkdirs()) {

      throw new IllegalStateException("Failed to create cache dir");

    }

    // 添加 shutdown hook，kill -15 pid 触发缓存清理

    shutdownHook = new Thread(() -> {

      CountDownLatch latch = new CountDownLatch();

      deleteCacheDir(ar -> latch.countDown());

      try {

        latch.await(, TimeUnit.SECONDS);

      } catch (Exception ignore) {

      }

    });

    Runtime.getRuntime().addShutdownHook(shutdownHook);

}

/**

  * 删除cache目录

  */

private void deleteCacheDir(Handler<AsyncResult<Void>> handler) {

    if (cacheDir != null && cacheDir.exists()) {

      vertx.fileSystem().deleteRecursive(cacheDir.getAbsolutePath(), true, handler);

    } else {

      handler.handle(Future.succeededFuture());

    }

}

/**

　*　解析文件

　*/

public File resolveFile(String fileName) {

    // 现在disk查找文件

    File file = new File(fileName);

    if (cwd != null && !file.isAbsolute()) {//是否是绝对路径

      file = new File(cwd, fileName);

    }

    // -Dvertx.disableFileCPResolving 设置

    if (!ENABLE_CP_RESOLVING) {

      return file;

    }

    /**

    　* synchronized同步块，防止多线程对cache directory操作导致线程安全问题

    　*/

    synchronized (this) {

      if (!file.exists()) {

        // 首先本地文件cache　查找

        File cacheFile = new File(cacheDir, fileName);

        if (enableCaching && cacheFile.exists()) {

          return cacheFile;

        }

        // 在classpath 查找

        ClassLoader cl = getClassLoader();

        //检查是否是UNIX separator,不是将文件路径 \ 替换为 /,不同操作系统 separator 存在差异

        if (NON_UNIX_FILE_SEP) {

          fileName = fileName.replace(FILE_SEP, "/");

        }

        String parentFileName = file.getParent();

        if (parentFileName != null) {

        //缓存父目录中存在的所有资源

          URL directoryContents = cl.getResource(parentFileName);

          if (directoryContents != null) {

            unpackUrlResource(directoryContents, parentFileName, cl, true);

          }

        }

        URL url = cl.getResource(fileName);

        if (url != null) {

          return unpackUrlResource(url, fileName, cl, false);

        }

      }

    }

    return file;

}

/**

  * 复制目录下所有文件到cacheDir目录下

  */

private File unpackUrlResource(URL url, String fileName, ClassLoader cl, boolean isDir) {

　　//获取协议

    String prot = url.getProtocol();

    switch (prot) {

      case "file":

        return unpackFromFileURL(url, fileName, cl);

      case "jar":

        return unpackFromJarURL(url, fileName, cl);

      case "bundle": // Apache Felix, Knopflerfish

      case "bundleentry": // Equinox

      case "bundleresource": // Equinox

        return unpackFromBundleURL(url, isDir);

      default:

        throw new IllegalStateException("Invalid url protocol: " + prot);

    }

}