java 7 NIO2（2） Metadata File Attributes

java 7 NIO2新特性支持操作文件的属性，使用NIO2的API操作你自己的文件元数据。

NIO2的属性操作相关类包

我们看下示例代码：

package com.mime;import java.io.IOException;import java.nio.ByteBuffer;import java.nio.charset.Charset;import java.nio.file.FileStore;import java.nio.file.FileSystem;import java.nio.file.FileSystems;import java.nio.file.Files;import java.nio.file.Path;import java.nio.file.Paths;import java.nio.file.attribute.AclEntry;import java.nio.file.attribute.AclEntryPermission;import java.nio.file.attribute.AclEntryType;import java.nio.file.attribute.AclFileAttributeView;import java.nio.file.attribute.BasicFileAttributeView;import java.nio.file.attribute.BasicFileAttributes;import java.nio.file.attribute.DosFileAttributes;import java.nio.file.attribute.FileAttribute;import java.nio.file.attribute.FileOwnerAttributeView;import java.nio.file.attribute.FileStoreAttributeView;import java.nio.file.attribute.FileTime;import java.nio.file.attribute.GroupPrincipal;import java.nio.file.attribute.PosixFileAttributeView;import java.nio.file.attribute.PosixFileAttributes;import java.nio.file.attribute.PosixFilePermission;import java.nio.file.attribute.PosixFilePermissions;import java.nio.file.attribute.UserDefinedFileAttributeView;import java.nio.file.attribute.UserPrincipal;import java.util.List;import java.util.Set;import static java.nio.file.LinkOption.NOFOLLOW_LINKS;public class NIO2FileAttribute {public static void main(String[] args) {FileSystem fs = FileSystems.getDefault();Set<String> views = fs.supportedFileAttributeViews();for (String view : views) {System.out.println(view);}/* * BasicFileAttributeView: This is a view of basic attributes that must * be supported by all file system implementations. The attribute view * name is basic. • DosFileAttributeView: This view provides the * standard four supported attributes on file systems that support the * DOS attributes. The attribute view name is dos. • * PosixFileAttributeView: This view extends the basic attribute view * with attributes supported on file systems that support the POSIX * (Portable Operating System Interface for Unix) family of standards, * such as Unix. The attribute view name is posix. • * FileOwnerAttributeView: This view is supported by any file system * implementation that supports the concept of a file owner. The * attribute view name is owner. • AclFileAttributeView: This view * supports reading or updating a file’s ACL. The NFSv4 ACL model is * supported. The attribute view name is acl. * UserDefinedFileAttributeView: This view enables support of metadata * that is user defined. */for (FileStore store : fs.getFileStores()) {boolean supported = store.supportsFileAttributeView(BasicFileAttributeView.class);System.out.println(store.name() + " ---" + supported);}Path path = null;try {path = Paths.get(System.getProperty("user.home"), "www","pyweb.settings");FileStore store = Files.getFileStore(path);boolean supported = store.supportsFileAttributeView("basic");System.out.println(store.name() + " ---" + supported);} catch (IOException e) {System.err.println(e);}BasicFileAttributes attr = null;try {attr = Files.readAttributes(path, BasicFileAttributes.class);} catch (IOException e) {System.err.println(e);}System.out.println("File size: " + attr.size());System.out.println("File creation time: " + attr.creationTime());System.out.println("File was last accessed at: "+ attr.lastAccessTime());System.out.println("File was last modified at: "+ attr.lastModifiedTime());System.out.println("Is directory? " + attr.isDirectory());System.out.println("Is  regular file? " + attr.isRegularFile());System.out.println("Is  symbolic link? " + attr.isSymbolicLink());System.out.println("Is  other? " + attr.isOther());// 只获取某个属性 [view-name:]attribute-name/** * Basic attribute names are listed here: lastModifiedTime * lastAccessTime creationTime size isRegularFile isDirectory * isSymbolicLink isOther fileKey **/try {long size = (Long) Files.getAttribute(path, "basic:size",java.nio.file.LinkOption.NOFOLLOW_LINKS);System.out.println("Size: " + size);} catch (IOException e) {System.err.println(e);}// Update a Basic Attributelong time = System.currentTimeMillis();FileTime fileTime = FileTime.fromMillis(time);try {Files.getFileAttributeView(path, BasicFileAttributeView.class).setTimes(fileTime, fileTime, fileTime);} catch (IOException e) {System.err.println(e);}try {Files.setLastModifiedTime(path, fileTime);} catch (IOException e) {System.err.println(e);}try {Files.setAttribute(path, "basic:lastModifiedTime", fileTime,NOFOLLOW_LINKS);Files.setAttribute(path, "basic:creationTime", fileTime,NOFOLLOW_LINKS);Files.setAttribute(path, "basic:lastAccessTime", fileTime,NOFOLLOW_LINKS);} catch (IOException e) {System.err.println(e);}// DosFileAttributeView DOS attributes can be acquired with the// following names:hidden readonly system archiveDosFileAttributes docattr = null;try {docattr = Files.readAttributes(path, DosFileAttributes.class);} catch (IOException e) {System.err.println(e);}System.out.println("Is read only ? " + docattr.isReadOnly());System.out.println("Is Hidden ? " + docattr.isHidden());System.out.println("Is archive ? " + docattr.isArchive());System.out.println("Is  system ? " + docattr.isSystem());// FileOwnerAttributeView// Set a File Owner Using Files.setOwner() 三种设置文件所有者的方法UserPrincipal owner = null;try {owner = path.getFileSystem().getUserPrincipalLookupService().lookupPrincipalByName("apress");Files.setOwner(path, owner);} catch (IOException e) {System.err.println(e);}FileOwnerAttributeView foav = Files.getFileAttributeView(path,FileOwnerAttributeView.class);try {owner = path.getFileSystem().getUserPrincipalLookupService().lookupPrincipalByName("apress");foav.setOwner(owner);} catch (IOException e) {System.err.println(e);}try {owner = path.getFileSystem().getUserPrincipalLookupService().lookupPrincipalByName("apress");Files.setAttribute(path, "owner:owner", owner, NOFOLLOW_LINKS);} catch (IOException e) {System.err.println(e);}// 获取文件所有者try {String ownerName = foav.getOwner().getName();System.out.println(ownerName);} catch (IOException e) {System.err.println(e);}try {UserPrincipal owner1 = (UserPrincipal) Files.getAttribute(path,"owner:owner", NOFOLLOW_LINKS);System.out.println(owner1.getName());} catch (IOException e) {System.err.println(e);}// POSIX View file owner, group owner, and nine related access// permissions (read, write, members of the same group, etc.). •group// permissionsPosixFileAttributes positattr = null;try {positattr = Files.readAttributes(path, PosixFileAttributes.class);} catch (IOException e) {System.err.println(e);}System.out.println("File owner: " + positattr.owner().getName());System.out.println("File group: " + positattr.group().getName());System.out.println("File permissions: "+ positattr.permissions().toString());// 设置文件访问权限FileAttribute<Set<PosixFilePermission>> posixattrs = PosixFilePermissions.asFileAttribute(positattr.permissions());try {Files.createFile(path, posixattrs);} catch (IOException e) {System.err.println(e);}Set<PosixFilePermission> permissions = PosixFilePermissions.fromString("rw-r--r--");try {Files.setPosixFilePermissions(path, permissions);} catch (IOException e) {System.err.println(e);}// 设置分组用户try {GroupPrincipal group = path.getFileSystem().getUserPrincipalLookupService().lookupPrincipalByGroupName("apressteam");Files.getFileAttributeView(path, PosixFileAttributeView.class).setGroup(group);} catch (IOException e) {System.err.println(e);}// 查询组用户try {GroupPrincipal group = (GroupPrincipal) Files.getAttribute(path,"posix:group", NOFOLLOW_LINKS);System.out.println(group.getName());} catch (IOException e) {System.err.println(e);}// ACL View access control list acl owner// 查询acl属性List<AclEntry> acllist = null;AclFileAttributeView aclview = Files.getFileAttributeView(path,AclFileAttributeView.class);try {acllist = aclview.getAcl();for (AclEntry aclentry : acllist) {System.out.println("++++++++++++++++++++++++++++++++++++++++++++++++++++");System.out.println("Principal: "+ aclentry.principal().getName());System.out.println("Type: " + aclentry.type().toString());System.out.println("Permissions: "+ aclentry.permissions().toString());System.out.println("Flags: " + aclentry.flags().toString());}} catch (Exception e) {System.err.println(e);}// 设置ACL属性try {// Lookup for the principalUserPrincipal user = path.getFileSystem().getUserPrincipalLookupService().lookupPrincipalByName("apress");// Get the ACL viewAclFileAttributeView view = Files.getFileAttributeView(path,AclFileAttributeView.class);// Create a new entryAclEntry entry = AclEntry.newBuilder().setType(AclEntryType.ALLOW).setPrincipal(user).setPermissions(AclEntryPermission.READ_DATA,AclEntryPermission.APPEND_DATA).build();// read ACLList<AclEntry> acl = view.getAcl();// Insert the new entryacl.add(0, entry);// rewrite ACLview.setAcl(acl);// or, like this// Files.setAttribute(path, "acl:acl", acl, NOFOLLOW_LINKS);} catch (IOException e) {System.err.println(e);}// File Store Attributes// 获取所有的fifilestore的属性信息FileSystem fs1 = FileSystems.getDefault();for (FileStore store : fs1.getFileStores()) {try {long total_space = store.getTotalSpace() / 1024;long used_space = (store.getTotalSpace() - store.getUnallocatedSpace()) / 1024;long available_space = store.getUsableSpace() / 1024;boolean is_read_only = store.isReadOnly();System.out.println("--- " + store.name() + " --- "+ store.type());System.out.println("Total space: " + total_space);System.out.println("Used space: " + used_space);System.out.println("Available space: " + available_space);System.out.println("Is read only? " + is_read_only);} catch (IOException e) {System.err.println(e);}}// 获取某个文件的fifilestore，再查询filestroe的属性信息try {FileStore store = Files.getFileStore(path);FileStoreAttributeView fsav = store.getFileStoreAttributeView(FileStoreAttributeView.class);} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}// User-Defined File Attributes View 用户自定义文件属性// 检测文件系统是否支持自定义属性try {FileStore store = Files.getFileStore(path);if (!store.supportsFileAttributeView(UserDefinedFileAttributeView.class)) {System.out.println("The user defined attributes are not supported on: "+ store);} else {System.out.println("The user defined attributes are supported on: "+ store);}} catch (IOException e) {System.err.println(e);}// 设置文件属性UserDefinedFileAttributeView udfav = Files.getFileAttributeView(path,UserDefinedFileAttributeView.class);try {int written = udfav.write("file.description",Charset.defaultCharset().encode("This file contains private information!"));System.out.println("write user defined file attribute return :"+ written);} catch (IOException e) {System.err.println(e);}// 获取文件的所有自定义属性try {for (String name : udfav.list()) {System.out.println(udfav.size(name) + "" + name);}} catch (IOException e) {System.err.println(e);}try {int size = udfav.size("file.description");ByteBuffer bb = ByteBuffer.allocateDirect(size);udfav.read("file.description", bb);bb.flip();System.out.println(Charset.defaultCharset().decode(bb).toString());} catch (IOException e) {System.err.println(e);}//删除自定义文件属性try {udfav.delete("file.description");} catch (IOException e) {System.err.println(e);}}}

在我的文件系统的输出

basicowneruserunixdosposix/dev/loop0 ---trueproc ---truesysfs ---truenone ---truenone ---truenone ---trueudev ---truedevpts ---truetmpfs ---truenone ---truenone ---truenone ---true/dev/sda6 ---truebinfmt_misc ---truegvfsd-fuse ---true/dev/sda5 ---truerootfs ---trueFile size: 265File creation time: 2012-12-29T12:53:35ZFile was last accessed at: 2012-12-29T12:53:35ZFile was last modified at: 2012-12-29T12:53:35ZIs directory? falseIs  regular file? trueIs  symbolic link? falseIs  other? falseSize: 265Is read only ? falseIs Hidden ? falseIs archive ? falseIs  system ? falsejava.nio.file.attribute.UserPrincipalNotFoundExceptionweijianzhongwjweijianzhongwjFile owner: weijianzhongwjjava.nio.file.attribute.UserPrincipalNotFoundExceptionjava.nio.file.attribute.UserPrincipalNotFoundExceptionFile group: weijianzhongwjFile permissions: [OWNER_WRITE, OTHERS_READ, GROUP_READ, OWNER_READ]java.nio.file.FileAlreadyExistsException: /home/weijianzhongwj/www/pyweb.settingsjava.nio.file.attribute.UserPrincipalNotFoundExceptionweijianzhongwjjava.lang.NullPointerExceptionjava.nio.file.attribute.UserPrincipalNotFoundException--- /dev/loop0 --- ext4Total space: 29979608Used space: 17216488Available space: 11240228Is read only? false--- proc --- procTotal space: 0Used space: 0Available space: 0Is read only? false--- sysfs --- sysfsTotal space: 0Used space: 0Available space: 0Is read only? false--- none --- fusectlTotal space: 0Used space: 0Available space: 0Is read only? false--- none --- debugfsTotal space: 0Used space: 0Available space: 0Is read only? false--- none --- securityfsTotal space: 0Used space: 0Available space: 0Is read only? false--- udev --- devtmpfsTotal space: 4063888Used space: 4Available space: 4063884Is read only? false--- devpts --- devptsTotal space: 0Used space: 0Available space: 0Is read only? false--- tmpfs --- tmpfsTotal space: 1628652Used space: 892Available space: 1627760Is read only? false--- none --- tmpfsTotal space: 5120Used space: 0Available space: 5120Is read only? false--- none --- tmpfsTotal space: 4071628Used space: 380Available space: 4071248Is read only? false--- none --- tmpfsTotal space: 102400Used space: 8Available space: 102392Is read only? false--- /dev/sda6 --- fuseblkTotal space: 164089852Used space: 101256692Available space: 62833160Is read only? false--- binfmt_misc --- binfmt_miscTotal space: 0Used space: 0Available space: 0Is read only? false--- gvfsd-fuse --- fuse.gvfsd-fuseTotal space: 0Used space: 0Available space: 0Is read only? false--- /dev/sda5 --- fuseblkTotal space: 102399704Used space: 81181588Available space: 21218116Is read only? falseThe user defined attributes are supported on: / (rootfs)write user defined file attribute return :3939file.descriptionThis file contains private information!