com.pervasive.datarush.io

Interface FileSystem

public interface FileSystem

Describes the file system identified by a path scheme. A Path points to a location (existing or not) on a FileSystem.

A FileSystem is rarely used directly. One only needs to be creating a new path scheme, in which case a FileSystemProvider must also be implemented.

Method Summary

Modifier and Type	Method and Description
InputStream	concat(List<Path> paths, boolean ignoreNonExistent) Returns an input stream consisting of the given list of paths concatenated together.
Path	createDirectories(Path path) Creates the directory identified by the given path, creating any necessary parent directories.
Path	createDirectory(Path path) Creates the directory identified by the given path.
boolean	createNewFile(Path path) Creates the file identified by the given path, if it doesn't already exist.
void	delete(Path path, boolean recursively) Deletes the file or directory identified by the specified path.
boolean	exists(Path path) Indicates whether the specified path represents an existing file or directory.
PathDetails	getDetails(Path path) Returns metadata associated with the specified path.
String	getFileSystemType(Path path) Returns an identifier for the filesystem type.
Object	getImplementation()
long	getLength(Path path) Returns the length of the file represented by the given path.
FileSystemProvider	getProvider() Gets the provider for the path scheme associated with the file system.
SplitIterator	getSplits(Path path, SplitOptions options) Computes data splits over the specified file.
boolean	isCreatable(Path path) Indicates whether the specified path can be created.
boolean	isDirectory(Path path) Indicates whether the specified path represents a directory.
boolean	isFile(Path path) Indicates whether the specified path represents a file.
boolean	isHidden(Path path) Indicates whether the associated path is hidden by the file system.
boolean	isReadable(Path path) Indicates whether the specified path can be read.
boolean	isWritable(Path path) Indicates whether the specified path can be written.
List<PathDetails>	listDirectory(Path path, DirectoryFilter filter) Gets the contents of the specified directory, applying a filter.
List<PathDetails>	matchPaths(String pattern) Gets all paths which match the given pattern.
boolean	move(FileSystem fromFS, Path from, Path to) Moves a file or directory from one location to another if possible.
FileChannel	newFileChannel(Path path) Opens the specified file for random access.
InputStream	newInputStream(Path path) Opens the specified file for reading.
OutputStream	newOutputStream(Path path, WriteMode mode) Opens the specified file for writing.
boolean	supportsConcat() Returns whether this filesystem supports the concat method.
boolean	supportsDirectories() Indicates whether the file system supports directories.
boolean	supportsRandomAccess() Indicates whether the file system supports random access to files.

Method Detail

getFileSystemType

String getFileSystemType(Path path)

Returns an identifier for the filesystem type. This identifier is used for reporting statistics to be able to distinguish local from non-local io.

Parameters:

path - the path

Returns:

a unique identifier

getProvider

FileSystemProvider getProvider()

Gets the provider for the path scheme associated with the file system.

Returns:

the associated provider object

supportsRandomAccess

boolean supportsRandomAccess()

Indicates whether the file system supports random access to files.

If a file system does not support random access, calling FileClient.newFileChannel(Path) will raise an error for paths referring to the file system.

Returns:

true if random access is supported, false otherwise.

supportsDirectories

boolean supportsDirectories()

Indicates whether the file system supports directories.

Returns:

true if directories are supported, false otherwise.

matchPaths

List<PathDetails> matchPaths(String pattern)
                      throws IOException

Gets all paths which match the given pattern. Patterns may be scheme-specific; refer to the provider implementation of a specific scheme to determine valid pattern syntax.

Parameters:

pattern - the file pattern to use

Returns:

all paths matching the pattern

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the pattern is not prefixed with a scheme supported by the provider

createDirectories

Path createDirectories(Path path)
                throws IOException

Creates the directory identified by the given path, creating any necessary parent directories.

Parameters:

path - the directory to create

Returns:

the path to the directory

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

createDirectory

Path createDirectory(Path path)
              throws IOException

Creates the directory identified by the given path. All parent directories must already exist. Use createDirectories(Path) if nonexistent parents need to be created.

Parameters:

path - the directory to create

Returns:

the path to the directory

Throws:

IOException - if I/O errors occur or if the parent directory does not exist

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

createNewFile

boolean createNewFile(Path path)
               throws IOException

Creates the file identified by the given path, if it doesn't already exist. All parent directories must already exist. Use createDirectories(Path) if nonexistent parents need to be created.

Parameters:

path - the directory to create

Returns:

true if the file was created, false if it already existed.

Throws:

IOException - if I/O errors occur or if the parent directory does not exist

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

delete

void delete(Path path,
            boolean recursively)
     throws IOException

Deletes the file or directory identified by the specified path. If the path is a directory, the contents will be deleted recursively as indicated. It is not an error to delete a non-existent path.

Parameters:

path - the file or directory to delete

recursively - indicates whether deletes of directories should recursively delete the contents

Throws:

IOException - if I/O errors occur or if the path identifies a non-empty directory and a recursive delete was not requested

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

move

boolean move(FileSystem fromFS,
             Path from,
             Path to)
      throws IOException

Moves a file or directory from one location to another if possible.

Parameters:

fromFS - TODO

from - the source location

to - the target location

Returns:

true if a move was possible (otherwise caller should fall back to copy-and-delete)

Throws:

IOException - if I/O errors occur

newInputStream

InputStream newInputStream(Path path)
                    throws IOException

Opens the specified file for reading. If the path identifies a directory, all files in the directory are read as a concatenated stream, in the order they are returned by #listFiles(Path). The read starts at the first byte of the (first) file. The returned stream is generally not buffered; consult specific implementations for details.

Parameters:

path - the file or directory to read

Returns:

a stream for reading the contents of the path

Throws:

IOException - if I/O errors occur

FileNotFoundException - if the specified path does not exist

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

newOutputStream

OutputStream newOutputStream(Path path,
                             WriteMode mode)
                      throws IOException

Opens the specified file for writing. Behavior depends on the provided mode and whether the target file exists. If the target file does not exist, it is created and the resulting stream is positioned at the first byte. Otherwise, if the target file exists:

• If the mode is CREATE_NEW, an error is raised.
• If the mode is OVERWRITE, the existing file is replaced with the byte written to the resulting stream.
• If the mode is APPEND, the resulting stream is positioned after the last byte of the existing file.

The returned stream is generally not buffered; consult specific implementations for details.

Parameters:

path - the file to write

mode - how to handle writes to existing files

Returns:

a stream for writing (or appending) the contents of the file

Throws:

IOException - if I/O errors occur or if the target is a directory

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

newFileChannel

FileChannel newFileChannel(Path path)
                    throws IOException

Opens the specified file for random access. Not all schemes support random access; consult specific implementations for details.

Parameters:

path - the file or directory to read

Returns:

a stream for reading the contents of the path

Throws:

IOException - if I/O errors occur

FileNotFoundException - if the specified path does not exist

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

exists

boolean exists(Path path)
        throws IOException

Indicates whether the specified path represents an existing file or directory.

Parameters:

path - the path to test

Returns:

true the path exists, false otherwise.

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

getDetails

PathDetails getDetails(Path path)
                throws IOException

Returns metadata associated with the specified path.

Parameters:

path - the path for which to get metadata

Returns:

metadata for the specified file system object, if it exists. null if it does not exist.

Throws:

IOException - if I/O errors occur

getLength

long getLength(Path path)
        throws IOException

Returns the length of the file represented by the given path.

Parameters:

path - the path to test

Returns:

the length of the file

Throws:

IOException - if I/O errors occur

isDirectory

boolean isDirectory(Path path)
             throws IOException

Indicates whether the specified path represents a directory.

Parameters:

path - the path to test

Returns:

true the path represents a directory,

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

isFile

boolean isFile(Path path)
        throws IOException

Indicates whether the specified path represents a file.

Parameters:

path - the path to test

Returns:

true the path represents a file,

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

isReadable

boolean isReadable(Path path)
            throws IOException

Indicates whether the specified path can be read.

Parameters:

path - the path to test

Returns:

true the path represents a readable file or directory, false otherwise.

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

isWritable

boolean isWritable(Path path)
            throws IOException

Indicates whether the specified path can be written.

Parameters:

path - the path to test

Returns:

true the path represents a readable file or directory, false otherwise.

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

isCreatable

boolean isCreatable(Path path)
             throws IOException

Indicates whether the specified path can be created.

Parameters:

path - the path to test

Returns:

true the path represents a nonexistent file or directory which could be created, false otherwise.

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

isHidden

boolean isHidden(Path path)
          throws IOException

Indicates whether the associated path is hidden by the file system.

Parameters:

path - the path to test

Returns:

true if the path is hidden, false otherwise.

Throws:

IOException - if I/O errors occur

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

listDirectory

List<PathDetails> listDirectory(Path path,
                                DirectoryFilter filter)
                         throws IOException

Gets the contents of the specified directory, applying a filter.

Parameters:

path - the directory for which to get a filtered content list

filter - a filter to apply to the contents

Returns:

all children of the directory which pass the filter

Throws:

IOException - if I/O errors occur or if the path identifies a file

IllegalArgumentException - if the path is not is not for a scheme supported by the provider

getSplits

SplitIterator getSplits(Path path,
                        SplitOptions options)
                 throws IOException

Computes data splits over the specified file. The supplied options are used to control the division of the file into splits, if the file system supports it.

If a provider can provide locality information, it should, as this can be used to guide distributed execution.

Parameters:

path - the file for which to get splits

options - configuration for the process of dividing the file

Returns:

an iterator generating the data splits over the target

Throws:

IOException - if an I/O error occurs

supportsConcat

boolean supportsConcat()

Returns whether this filesystem supports the concat method.

Returns:

whether this filesystem supports the concat method

concat

InputStream concat(List<Path> paths,
                   boolean ignoreNonExistent)
            throws IOException

Returns an input stream consisting of the given list of paths concatenated together. Most filesystem implementations should not need to implement this method. This is an optimization for remote filesystems to perform a bulk-fetch.

Parameters:

paths - the list of paths

ignoreNonExistent - whether to skip non-existent files

Returns:

a concatenated input stream

Throws:

IOException

UnsupportedOperationException - If this filesystem does not support concatenation.

getImplementation

Object getImplementation()