VirtualFile (Apache Derby V10.14 Internals)

java.lang.Object
- org.apache.derby.impl.io.vfmem.VirtualFile

All Implemented Interfaces:

StorageFile
```
public class VirtualFile
extends java.lang.Object
implements StorageFile
```
Represents a file in the virtual file system.
A virtual file is not created until one of the following methods are invoked:
- createNewFile
- getOutputStream
- getRandomAccessFile
- mkdir
- mkdirs
When a method that requires access to the file data or to know if the file exists or not, the associated data store is consulted.

Field Summary

Fields
Modifier and Type Field Description

private DataStore dStore
The data store this virtual file belongs to.

private java.lang.String path
The path of this virtual file.
- Fields inherited from interface org.apache.derby.io.StorageFile
  EXCLUSIVE_FILE_LOCK, EXCLUSIVE_FILE_LOCK_NOT_AVAILABLE, NO_FILE_LOCK_SUPPORT

Fields
Modifier and Type	Field	Description
`private DataStore`	`dStore`	The data store this virtual file belongs to.
`private java.lang.String`	`path`	The path of this virtual file.

Constructor Summary

Constructors
Constructor Description

VirtualFile(java.lang.String path, DataStore dbData)
Creates a new virtual file handle.

Constructors
Constructor	Description
`VirtualFile(java.lang.String path, DataStore dbData)`	Creates a new virtual file handle.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`canWrite()`	Tells if this file can be written to.
`boolean`	`createNewFile()`	Creates the the file denoted by this virtual file object.
`boolean`	`delete()`	Deletes this file, of if exists.
`boolean`	`deleteAll()`	Deletes the path denoted by this file and all its contents, including sub directories.
`boolean`	`exists()`	Tells if this file exists.
`java.lang.String`	`getCanonicalPath()`	Converts this StorageFile into a canonical pathname string.
`private DataStoreEntry`	`getEntry()`	Returns the data store entry denoted by this file, if it exists.
`int`	`getExclusiveFileLock()`	Get an exclusive lock with this name.
`java.io.InputStream`	`getInputStream()`	Returns an input stream for the file denoted.
`java.lang.String`	`getName()`
`java.io.OutputStream`	`getOutputStream()`	Obtains an output stream for the file denoted.
`java.io.OutputStream`	`getOutputStream(boolean append)`	Obtains an output stream for the file denoted.
`StorageFile`	`getParentDir()`	Get the name of the parent directory if this name includes a parent.
`java.lang.String`	`getPath()`	Returns the path of this file.
`StorageRandomAccessFile`	`getRandomAccessFile(java.lang.String mode)`	Creates a random access file that can be used to read and write from/into the file.
`boolean`	`isDirectory()`	Tells if this file is a directory.
`long`	`length()`	Returns the length of the file.
`void`	`limitAccessToOwner()`	Use when creating a new file.
`java.lang.String[]`	`list()`	Returns the contents of the directory denoted by this file, including any sub directories and their contents.
`boolean`	`mkdir()`	Creates the directory denoted by this virtual file if it doesn't exist.
`boolean`	`mkdirs()`	Creates the directory and any parent directories denoted by this virtual file.
`void`	`releaseExclusiveFileLock()`	Release the resource associated with an earlier acquired exclusive lock releaseExclusiveFileLock() may delete the file
`boolean`	`renameTo(StorageFile newName)`	Renames the file denoted by this handle.
`boolean`	`setReadOnly()`	Make the named file or directory read-only.
`java.lang.String`	`toString()`	Returns a textual representation of this file.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - path
```
private final java.lang.String path
```
    The path of this virtual file.
  - dStore
```
private final DataStore dStore
```
    The data store this virtual file belongs to.
- Constructor Detail
  - VirtualFile
```
public VirtualFile(java.lang.String path,
                   DataStore dbData)
```
    Creates a new virtual file handle.
    
    Parameters:
    
    path - the path of this virtual file
    
    dbData - the store this handle belongs to
- Method Detail
  - list
```
public java.lang.String[] list()
```
    Returns the contents of the directory denoted by this file, including any sub directories and their contents.
    
    Specified by:
    
    list in interface StorageFile
    
    Returns:
    
    A list of all files and directories, or null if this file doesn't denote a directory or doesn't exist.
  - canWrite
```
public boolean canWrite()
```
    Tells if this file can be written to.
    
    Specified by:
    
    canWrite in interface StorageFile
    
    Returns:
    
    true if this file exists and can be written to, false otherwise.
  - exists
```
public boolean exists()
```
    Tells if this file exists.
    
    Specified by:
    
    exists in interface StorageFile
    
    Returns:
    
    true if this file exists, false otherwise.
  - isDirectory
```
public boolean isDirectory()
```
    Tells if this file is a directory.
    Note that false is returned if this path doesn't exist.
    
    Specified by:
    
    isDirectory in interface StorageFile
    
    Returns:
    
    true if this file represents an existing directoy, false otherwise.
  - delete
```
public boolean delete()
```
    Deletes this file, of if exists.
    
    Specified by:
    
    delete in interface StorageFile
    
    Returns:
    
    true if this file exists and is successfully deleted, false otherwise.
  - deleteAll
```
public boolean deleteAll()
```
    Deletes the path denoted by this file and all its contents, including sub directories.
    
    Specified by:
    
    deleteAll in interface StorageFile
    
    Returns:
    
    true if this file and all contents are successfully deleted, false otherwise.
  - getPath
```
public java.lang.String getPath()
```
    Returns the path of this file.
    
    Specified by:
    
    getPath in interface StorageFile
    
    Returns:
    
    The path of this file.
    
    See Also:
    
    StorageFactory.getSeparator()
  - getCanonicalPath
```
public java.lang.String getCanonicalPath()
```
    Description copied from interface: StorageFile
    
    Converts this StorageFile into a canonical pathname string. The form of the canonical path is system dependent.
    
    Specified by:
    
    getCanonicalPath in interface StorageFile
    
    Returns:
    
    The pathname as a string.
  - getName
```
public java.lang.String getName()
```
    Specified by:
    
    getName in interface StorageFile
    
    Returns:
    
    The last segment in the path name, "" if the path name sequence is empty.
  - createNewFile
```
public boolean createNewFile()
```
    Creates the the file denoted by this virtual file object.
    
    Specified by:
    
    createNewFile in interface StorageFile
    
    Returns:
    
    true if the file was successfully created, false otherwise
  - renameTo
```
public boolean renameTo(StorageFile newName)
```
    Renames the file denoted by this handle.
    
    Specified by:
    
    renameTo in interface StorageFile
    
    Parameters:
    
    newName - the new name
    
    Returns:
    
    true if the fail was renamed, false otherwise
  - mkdir
```
public boolean mkdir()
```
    Creates the directory denoted by this virtual file if it doesn't exist.
    For the directory to be created, it cannot exist already (either as a file or a directory), and any parent directories must exist.
    
    Specified by:
    
    mkdir in interface StorageFile
    
    Returns:
    
    true if the directory was created, false otherwise.
  - mkdirs
```
public boolean mkdirs()
```
    Creates the directory and any parent directories denoted by this virtual file.
    For the directory to be created, it cannot exist already (either as a file or a directory), and all the parent elements most denote either existing directories or non-existing paths.
    
    Specified by:
    
    mkdirs in interface StorageFile
    
    Returns:
    
    true if the directory was created, false otherwise.
  - length
```
public long length()
```
    Returns the length of the file.
    If the file doesn't exists, or is a directory, 0 is returned.
    
    Returns:
    
    The length of the existing file, or 0 if the path denotes a directory or a non-existing file.
  - getParentDir
```
public StorageFile getParentDir()
```
    Description copied from interface: StorageFile
    
    Get the name of the parent directory if this name includes a parent.
    
    Specified by:
    
    getParentDir in interface StorageFile
    
    Returns:
    
    An StorageFile denoting the parent directory of this StorageFile, if it has a parent, null if it does not have a parent.
  - setReadOnly
```
public boolean setReadOnly()
```
    Description copied from interface: StorageFile
    
    Make the named file or directory read-only. This interface does not specify whether this also makes the file undeletable.
    
    Specified by:
    
    setReadOnly in interface StorageFile
    
    Returns:
    
    true if the named file or directory was made read-only, or it already was read-only; false if not.
  - getOutputStream
```
public java.io.OutputStream getOutputStream()
                                     throws java.io.FileNotFoundException
```
    Obtains an output stream for the file denoted.
    If the file already exists, it will be truncated.
    
    Specified by:
    
    getOutputStream in interface StorageFile
    
    Returns:
    
    An OutputStream-instance.
    
    Throws:
    
    java.io.FileNotFoundException - if the denoted path is a directory, the file is read-only, the file cannot be created or any other reason why an OutputStream cannot be created for the file
  - getOutputStream
```
public java.io.OutputStream getOutputStream(boolean append)
                                     throws java.io.FileNotFoundException
```
    Obtains an output stream for the file denoted.
    
    Specified by:
    
    getOutputStream in interface StorageFile
    
    Parameters:
    
    append - tells if the file should be appended or truncated
    
    Returns:
    
    An OutputStream-instance.
    
    Throws:
    
    java.io.FileNotFoundException - if the denoted path is a directory, the file is read-only, the file cannot be created or any other reason why an OutputStream cannot be created for the file
  - getInputStream
```
public java.io.InputStream getInputStream()
                                   throws java.io.FileNotFoundException
```
    Returns an input stream for the file denoted.
    
    Specified by:
    
    getInputStream in interface StorageFile
    
    Returns:
    
    An InputStream instance.
    
    Throws:
    
    java.io.FileNotFoundException - if the file doesn't exists or it is a directory
  - getExclusiveFileLock
```
public int getExclusiveFileLock()
                         throws StandardException
```
    Description copied from interface: StorageFile
    
    Get an exclusive lock with this name. This is used to ensure that two or more JVMs do not open the same database at the same time. ny StorageFile that has getExclusiveFileLock() called on it is not intended to be read from or written to. It's sole purpose is to provide a locked entity to avoid multiple instances of Derby accessing the same database. getExclusiveFileLock() may delete or overwrite any existing file.
    
    Specified by:
    
    getExclusiveFileLock in interface StorageFile
    
    Returns:
    
    EXCLUSIVE_FILE_LOCK_NOT_AVAILABLE if the lock cannot be acquired because it is already held.
    EXCLUSIVE_FILE_LOCK if the lock was successfully acquired.
    NO_FILE_LOCK_SUPPORT if the system does not support exclusive locks.
    
    Throws:
    
    StandardException
  - releaseExclusiveFileLock
```
public void releaseExclusiveFileLock()
```
    Description copied from interface: StorageFile
    
    Release the resource associated with an earlier acquired exclusive lock releaseExclusiveFileLock() may delete the file
    
    Specified by:
    
    releaseExclusiveFileLock in interface StorageFile
    
    See Also:
    
    StorageFile.getExclusiveFileLock()
  - getRandomAccessFile
```
public StorageRandomAccessFile getRandomAccessFile(java.lang.String mode)
                                            throws java.io.FileNotFoundException
```
    Creates a random access file that can be used to read and write from/into the file.
    
    Specified by:
    
    getRandomAccessFile in interface StorageFile
    
    Parameters:
    
    mode - file mode, one of "r", "rw", "rws" or "rwd" (lower-case letters are required)
    
    Returns:
    
    A StorageRandomAccessFile-instance.
    
    Throws:
    
    java.lang.IllegalArgumentException - if the specificed mode is invalid
    
    java.io.FileNotFoundException - if the file denoted is a directory,
    
    See Also:
    
    java.io.RandomAccessFile
  - toString
```
public java.lang.String toString()
```
    Returns a textual representation of this file.
    
    Overrides:
    
    toString in class java.lang.Object
    
    Returns:
    
    Textual representation.
  - getEntry
```
private DataStoreEntry getEntry()
```
    Returns the data store entry denoted by this file, if it exists.
    
    Returns:
    
    The assoiciated DataStoreEntry if it exists, null if it doesn't exist.
  - limitAccessToOwner
```
public void limitAccessToOwner()
```
    Description copied from interface: StorageFile
    
    Use when creating a new file. By default, a file created in an underlying file system, if applicable, will have read and write access for the file owner unless the property derby.useDefaultFilePermissions is set to true.
    
    Specified by:
    
    limitAccessToOwner in interface StorageFile

Class VirtualFile

Field Summary

Fields inherited from interface org.apache.derby.io.StorageFile

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

path

dStore

Constructor Detail

VirtualFile

Method Detail

list

canWrite

exists

isDirectory

delete

deleteAll

getPath

getCanonicalPath

getName

createNewFile

renameTo

mkdir

mkdirs

length

getParentDir

setReadOnly

getOutputStream

getOutputStream

getInputStream

getExclusiveFileLock

releaseExclusiveFileLock

getRandomAccessFile

toString

getEntry

limitAccessToOwner