Java7的Zip工具类：Zip File System Provider

  项目中涉及从银行下载Zip类型的对账文件。基于面向谷歌的编程，搜索一下，发现好多Zip工具类还是基于 java.util.zip.ZipEntry。其实Java 7的引入的Zip工具类优雅很多： Zip File System Provider。 废话少说。下面分别展示一下Zip的解压、创建、遍历。

import java.io.IOException;import java.net.URI;import java.nio.file.FileSystem;import java.nio.file.FileSystems;import java.nio.file.FileVisitResult;import java.nio.file.Files;import java.nio.file.Path;import java.nio.file.Paths;import java.nio.file.SimpleFileVisitor;import java.nio.file.StandardCopyOption;import java.nio.file.attribute.BasicFileAttributes;import java.text.DateFormat;import java.text.SimpleDateFormat;import java.util.Date;import java.util.HashMap;import java.util.Map;public class ZipUtil {  /**   * Returns a zip file system   *   * @param zipFilename to construct the file system from   * @param create true if the zip file should be created   * @return a zip file system   */  private static FileSystem createZipFileSystem(String zipFilename,      boolean create)      throws IOException {    // convert the filename to a URI    final Path path = Paths.get(zipFilename);    final URI uri = URI.create("jar:file:" + path.toUri().getPath());    final Map<String, String> env = new HashMap<>();    if (create) {      env.put("create", "true");    }    return FileSystems.newFileSystem(uri, env);  }  /**   * Unzips the specified zip file to the specified destination directory.   * Replaces any files in the destination, if they already exist.   *   * @param zipFilename the name of the zip file to extract   * @param destDirname the directory to unzip to   */  public static void unzip(String zipFilename, String destDirname)      throws IOException {    final Path destDir = Paths.get(destDirname);    //if the destination doesn't exist, create it    if (Files.notExists(destDir)) {      System.out.println(destDir + " does not exist. Creating...");      Files.createDirectories(destDir);    }    try (FileSystem zipFileSystem = createZipFileSystem(zipFilename, false)) {      final Path root = zipFileSystem.getPath("/");      //walk the zip file tree and copy files to the destination      Files.walkFileTree(root, new SimpleFileVisitor<Path>() {        @Override        public FileVisitResult visitFile(Path file,            BasicFileAttributes attrs) throws IOException {          final Path destFile = Paths.get(destDir.toString(),              file.toString());          System.out.printf("Extracting file %s to %s\n", file, destFile);          Files.copy(file, destFile, StandardCopyOption.REPLACE_EXISTING);          return FileVisitResult.CONTINUE;        }        @Override        public FileVisitResult preVisitDirectory(Path dir,            BasicFileAttributes attrs) throws IOException {          final Path dirToCreate = Paths.get(destDir.toString(),              dir.toString());          if (Files.notExists(dirToCreate)) {            System.out.printf("Creating directory %s\n", dirToCreate);            Files.createDirectory(dirToCreate);          }          return FileVisitResult.CONTINUE;        }      });    }  }  /**   * Creates/updates a zip file.   *   * @param zipFilename the name of the zip to create   * @param filenames list of filename to add to the zip   */  public static void create(String zipFilename, String... filenames)      throws IOException {    try (FileSystem zipFileSystem = createZipFileSystem(zipFilename, true)) {      final Path root = zipFileSystem.getPath("/");      //iterate over the files we need to add      for (String filename : filenames) {        final Path src = Paths.get(filename);        //add a file to the zip file system        if (!Files.isDirectory(src)) {          final Path dest = zipFileSystem.getPath(root.toString(),              src.toString());          final Path parent = dest.getParent();          if (Files.notExists(parent)) {            System.out.printf("Creating directory %s\n", parent);            Files.createDirectories(parent);          }          Files.copy(src, dest, StandardCopyOption.REPLACE_EXISTING);        } else {          //for directories, walk the file tree          Files.walkFileTree(src, new SimpleFileVisitor<Path>() {            @Override            public FileVisitResult visitFile(Path file,                BasicFileAttributes attrs) throws IOException {              final Path dest = zipFileSystem.getPath(root.toString(),                  file.toString());              Files.copy(file, dest, StandardCopyOption.REPLACE_EXISTING);              return FileVisitResult.CONTINUE;            }            @Override            public FileVisitResult preVisitDirectory(Path dir,                BasicFileAttributes attrs) throws IOException {              final Path dirToCreate = zipFileSystem.getPath(root.toString(),                  dir.toString());              if (Files.notExists(dirToCreate)) {                System.out.printf("Creating directory %s\n", dirToCreate);                Files.createDirectories(dirToCreate);              }              return FileVisitResult.CONTINUE;            }          });        }      }    }  }  /**   * List the contents of the specified zip file   */  public static void list(String zipFilename) throws IOException {    System.out.printf("Listing Archive:  %s\n", zipFilename);    //create the file system    try (FileSystem zipFileSystem = createZipFileSystem(zipFilename, false)) {      final Path root = zipFileSystem.getPath("/");      //walk the file tree and print out the directory and filenames      Files.walkFileTree(root, new SimpleFileVisitor<Path>() {        @Override        public FileVisitResult visitFile(Path file,            BasicFileAttributes attrs) throws IOException {          print(file);          return FileVisitResult.CONTINUE;        }        @Override        public FileVisitResult preVisitDirectory(Path dir,            BasicFileAttributes attrs) throws IOException {          print(dir);          return FileVisitResult.CONTINUE;        }        /**         * prints out details about the specified path         * such as size and modification time         * @param file         * @throws IOException         */        private void print(Path file) throws IOException {          final DateFormat df = new SimpleDateFormat("MM/dd/yyyy-HH:mm:ss");          final String modTime = df.format(new Date(              Files.getLastModifiedTime(file).toMillis()));          System.out.printf("%d  %s  %s\n",              Files.size(file),              modTime,              file);        }      });    }  }}