org.apache.lucene.store

Class Directory

Known Direct Subclasses:
FSDirectory, RAMDirectory

public abstract class Directory
extends Object

A Directory is a flat list of files. Files may be written once, when they are created. Once a file is created it may only be opened for read, or deleted. Random access is permitted both when reading and writing.

Java's i/o APIs not used directly, but rather all i/o is through this API. This permits things such as:

Directory locking is implemented by an instance of LockFactory, and can be changed for each Directory instance using setLockFactory(LockFactory).
Author:
Doug Cutting

Field Summary

protected LockFactory
lockFactory
Holds the LockFactory instance (implements locking for this Directory instance).

Method Summary

void
clearLock(String name)
Attempt to clear (forcefully unlock and remove) the specified lock.
abstract void
close()
Closes the store.
static void
copy(Directory src, Directory dest, boolean closeDirSrc)
Copy contents of a directory src to a directory dest.
abstract IndexOutput
createOutput(String name)
Creates a new, empty file in the directory with the given name.
abstract void
deleteFile(String name)
Removes an existing file in the directory.
abstract boolean
fileExists(String name)
Returns true iff a file with the given name exists.
abstract long
fileLength(String name)
Returns the length of a file in the directory.
abstract long
fileModified(String name)
Returns the time the named file was last modified.
LockFactory
getLockFactory()
Get the LockFactory that this Directory instance is using for its locking implementation.
String
getLockID()
Return a string identifier that uniquely differentiates this Directory instance from other Directory instances.
abstract String[]
list()
Returns an array of strings, one for each file in the directory.
Lock
makeLock(String name)
Construct a Lock.
abstract IndexInput
openInput(String name)
Returns a stream reading an existing file.
abstract void
renameFile(String from, String to)
Deprecated.
void
setLockFactory(LockFactory lockFactory)
Set the LockFactory that this Directory instance should use for its locking implementation.
abstract void
touchFile(String name)
Set the modified time of an existing file to now.

Field Details

lockFactory

protected LockFactory lockFactory
Holds the LockFactory instance (implements locking for this Directory instance).

Method Details

clearLock

public void clearLock(String name)
            throws IOException
Attempt to clear (forcefully unlock and remove) the specified lock. Only call this at a time when you are certain this lock is no longer in use.
Parameters:

close

public abstract void close()
            throws IOException
Closes the store.

copy

public static void copy(Directory src,
                        Directory dest,
                        boolean closeDirSrc)
            throws IOException
Copy contents of a directory src to a directory dest. If a file in src already exists in dest then the one in dest will be blindly overwritten.
Parameters:
src - source directory
dest - destination directory
closeDirSrc - if true, call close() method on source directory

createOutput

public abstract IndexOutput createOutput(String name)
            throws IOException
Creates a new, empty file in the directory with the given name. Returns a stream writing this file.

deleteFile

public abstract void deleteFile(String name)
            throws IOException
Removes an existing file in the directory.

fileExists

public abstract boolean fileExists(String name)
            throws IOException
Returns true iff a file with the given name exists.

fileLength

public abstract long fileLength(String name)
            throws IOException
Returns the length of a file in the directory.

fileModified

public abstract long fileModified(String name)
            throws IOException
Returns the time the named file was last modified.

getLockFactory

public LockFactory getLockFactory()
Get the LockFactory that this Directory instance is using for its locking implementation. Note that this may be null for Directory implementations that provide their own locking implementation.

getLockID

public String getLockID()
Return a string identifier that uniquely differentiates this Directory instance from other Directory instances. This ID should be the same if two Directory instances (even in different JVMs and/or on different machines) are considered "the same index". This is how locking "scopes" to the right index.

list

public abstract String[] list()
            throws IOException
Returns an array of strings, one for each file in the directory.

makeLock

public Lock makeLock(String name)
Construct a Lock.
Parameters:
name - the name of the lock file

openInput

public abstract IndexInput openInput(String name)
            throws IOException
Returns a stream reading an existing file.

renameFile

public abstract void renameFile(String from,
                                String to)
            throws IOException

Deprecated.

Renames an existing file in the directory. If a file already exists with the new name, then it is replaced. This replacement is not guaranteed to be atomic.

setLockFactory

public void setLockFactory(LockFactory lockFactory)
Set the LockFactory that this Directory instance should use for its locking implementation. Each * instance of LockFactory should only be used for one directory (ie, do not share a single instance across multiple Directories).
Parameters:
lockFactory - instance of LockFactory.

touchFile

public abstract void touchFile(String name)
            throws IOException
Set the modified time of an existing file to now.

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