前言
自从1.7版本开始，Java引入了Nio包，提供了更强大的IO功能。 本文简单介绍如何用java.nio.file.attribute下的工具类修改文件的权限，用户和组。因为本类库是针对Posix类系统的的，所以主要适用于Linux和Mac上（实测Win7不支持）。
测试样例
测试代码如下：
public class FileTest {
public static void main(String[] args) throws Exception { // 检查操作系统是否支持posix。 // 一般像mac和linux都支持，经测试win7不支持 boolean supportPosix = FileSystems.getDefault().supportedFileAttributeViews().contains("posix"); if (!supportPosix) { System.out.println("Your OS does not support posix."); return; } // 将要设置的权限：用户，组，以及三组读/写/执行的权限 String owner = "testowner"; String group = "testgroup"; PosixFilePermission[] permissions = { PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE, PosixFilePermission.OWNER_EXECUTE, PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE, PosixFilePermission.GROUP_EXECUTE, PosixFilePermission.OTHERS_READ, PosixFilePermission.OTHERS_WRITE, PosixFilePermission.OTHERS_EXECUTE, }; changePermission("/opt/test", true, owner, group, permissions); } private static void changePermission(String pathStr, boolean isRecurisive, String owner, String group, PosixFilePermission... permissions) { Path path = Paths.get(pathStr); if (!Files.exists(path)) { System.out.println(pathStr + " not exists!"); return; }; try { System.out.format("Before, %s ", pathStr); readTargetPermission(path); // 设置permission，相当于linux命令chmod Set<PosixFilePermission> perms = new HashSet<>(); for (PosixFilePermission permission : permissions) { perms.add(permission); } Files.setPosixFilePermissions(path, perms); // 设置用户和组，相当于linux命令chown // 要保证用户和组存在，否则lookupService会抛UserPrincipalNotFoundException UserPrincipalLookupService lookupService = FileSystems.getDefault().getUserPrincipalLookupService(); GroupPrincipal groupPrincipal = lookupService.lookupPrincipalByGroupName(group); UserPrincipal userPrincipal = lookupService.lookupPrincipalByName(owner); PosixFileAttributeView view = Files.getFileAttributeView(path, PosixFileAttributeView.class); view.setGroup(groupPrincipal); view.setOwner(userPrincipal); System.out.format("After, %s ", pathStr); readTargetPermission(path); } catch (IOException e) { if (e instanceof UserPrincipalNotFoundException) { System.out.format("group '%s' or owner '%s' not exist%n", group, owner); return; } System.out.format("%s set permission failed%n", pathStr); e.printStackTrace(); } // 当是目录的时候，递归设置文件权限 if (isRecurisive && Files.isDirectory(path)) { try (DirectoryStream<Path> ds = Files.newDirectoryStream(path)) { for (Path subPath : ds) { changePermission(pathStr + File.separator + subPath.getFileName(), true, owner, group, permissions); } } catch (IOException e) { e.printStackTrace(); } } } // print current permission of folder/file private static void readTargetPermission(Path path) throws IOException { Set<PosixFilePermission> filePermissions = Files.readAttributes(path, PosixFileAttributes.class).permissions(); GroupPrincipal fileGroup = Files.readAttributes(path, PosixFileAttributes.class).group(); UserPrincipal fileOwner = Files.readAttributes(path, PosixFileAttributes.class).owner(); System.out.format("permissions: %s, user: %s, group: %s%n", PosixFilePermissions.toString(filePermissions), fileOwner, fileGroup); } } 控制台输出如下：
Before, /opt/test permissions: rwx------, user: root, group: root After, /opt/test permissions: rwxrwxrwx, user: testowner, group: testgroup Before, /opt/test/testFolder permissions: rwx------, user: root, group: root After, /opt/test/testFolder permissions: rwxrwxrwx, user: testowner, group: testgroup Before, /opt/test/testFolder/testFile2 permissions: rw-------, user: root, group: root After, /opt/test/testFolder/testFile2 permissions: rwxrwxrwx, user: testowner, group: testgroup Before, /opt/test/testFile permissions: rw-------, user: root, group: root After, /opt/test/testFile permissions: rwxrwxrwx, user: testowner, group: testgroup 通过对比，目录以及该目录下的所有子目录和文件，权限都变成了777，用户都由root变为了testowner，组都有root变为了testgroup。
总结
Java Nio提供了强大及友好的类库，方便我们对文件进行各种操作。
来源：真相只有一个