apache-comnons系列之commons-vfs2 学习笔记

apache-comnons系列之commons-vfs2 学习笔记

概述

• 参考
  
  • http://p7engqingyang.iteye.com/blog/1702429
  • http://blog.youkuaiyun.com/ffm83/article/details/42080387

VFS

• The main entry point for the VFS. Used to create {@link FileSystemManager} instances.

FileSystemManager

• A FileSystemManager manages a set of file systems. This interface is used to locate a {@link FileObject} by name from one of those file systems.
• A file system manager can recognise several types of file names
  
  • Absolute URI(file:/c:/somefile)
  • Absolute local file name(/home/someuser/a-file)
  • Relative path(../somefile)

StandardFileSystemManager—->DefaultFileSystemManager—->FileSystemManager

• A {@link org.apache.commons.vfs2.FileSystemManager} that configures itself from an XML (Default: providers.xml) configuration file.

FileSystem

• A file system, made up of a hierarchy of files.

LocalFileSystem—->AbstractFileSystem—->FileSystem

• A local file system.
• String rootFile
• resolveFile(委托底层文件系统创建/解析文件)
  
  • org.apache.commons.vfs2.provider.local.LocalFileSystem.createFile

FileObject

• Represents a file, and is used to access the content and structure of the file

LocalFile—->AbstractFileObject—->FileObject

• A file object implementation which uses direct file access.
• String rootFile;
• File file;
• org.apache.commons.vfs2.provider.local.LocalFile.doAttach(核心方法,将路径与文件绑定)
• org.apache.commons.vfs2.provider.local.LocalFile.doGetInputStream(底层获取输入流,fs委托其获取)
• org.apache.commons.vfs2.provider.local.LocalFile.doGetOutputStream(底层获取输出流,fs委托其获取)

HdfsFileObject—->AbstractFileObject—->FileObject

• A VFS representation of an HDFS file.
• FileSystem hdfs;(委托给hadoop进行底层操作)

FileProvider

• A file provider. Each file provider is responsible for handling files for a particular URI scheme.

DefaultLocalFileProvider—->LocalFileProvider

• DefaultLocalFileProvider—->AbstractOriginatingFileProvider—->AbstractFileProvider
• A file system provider, which uses direct file access.

VfsComponent

• This interface is used to manage the lifecycle of all VFS components.
• init/close
• This includes all implementations of the following interfaces:
  
  • org.apache.commons.vfs2.provider.FileProvider
  • org.apache.commons.vfs2.FileSystem
  • org.apache.commons.vfs2.provider.FileReplicator
  • org.apache.commons.vfs2.provider.TemporaryFileStore

FileReplicator

• Responsible for making local replicas of files.

DefaultFileReplicator

VfsComponentContext

• Allows VFS components to access the services they need, such as the file replicator. A VFS component is supplied with a context as part of its initialisation.

DefaultVfsComponentContext

• DefaultFileSystemManager manager

测试

• org.apache.commons.vfs2.VFS(入口)
  
  • org.apache.commons.vfs2.VFS.getManager
  • createManager(“org.apache.commons.vfs2.impl.StandardFileSystemManager”)
• org.apache.commons.vfs2.impl.test.DefaultFileSystemManagerTest
  
  • providers = new HashMap();
  • components = new ArrayList();
  • LocalFileProvider localFileProvider;
  • FileProvider defaultProvider;
  • org.apache.commons.vfs2.impl.StandardFileSystemManager.init(初始化方法从providers.xml或者META-INF/vfs-providers.xml进行provider等信息的加载与配置)
  • org.apache.commons.vfs2.impl.StandardFileSystemManager.configure(org.w3c.dom.Element)
  • org.apache.commons.vfs2.impl.DefaultFileSystemManager.resolveFile(java.lang.String)