public abstract class

Directory

extends Object
implements Closeable
java.lang.Object
   ↳ org.apache.lucene.store.Directory
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

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:

  • implementation of RAM-based indices;
  • implementation indices stored in a database, via JDBC;
  • implementation of an index as a single file;
Directory locking is implemented by an instance of LockFactory, and can be changed for each Directory instance using setLockFactory(LockFactory).

Summary

Fields
protected boolean isOpen
protected LockFactory lockFactory Holds the LockFactory instance (implements locking for this Directory instance).
Public Constructors
Directory()
Public Methods
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[] listAll()
Returns an array of strings, one for each file in the directory.
Lock makeLock(String name)
Construct a Lock.
IndexInput openInput(String name, int bufferSize)
Returns a stream reading an existing file, with the specified read buffer size.
abstract IndexInput openInput(String name)
Returns a stream reading an existing file.
void setLockFactory(LockFactory lockFactory)
Set the LockFactory that this Directory instance should use for its locking implementation.
void sync(String name)
Ensure that any writes to this file are moved to stable storage.
String toString()
abstract void touchFile(String name)
Set the modified time of an existing file to now.
Protected Methods
final void ensureOpen()
[Expand]
Inherited Methods
From class java.lang.Object
From interface java.io.Closeable

Fields

protected boolean isOpen

protected LockFactory lockFactory

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

Public Constructors

public Directory ()

Public Methods

public void clearLock (String name)

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
name name of the lock to be cleared.
Throws
IOException

public abstract void close ()

Closes the store.

Throws
IOException

public static void copy (Directory src, Directory dest, boolean closeDirSrc)

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.

NOTE: the source directory cannot change while this method is running. Otherwise the results are undefined and you could easily hit a FileNotFoundException.

NOTE: this method only copies files that look like index files (ie, have extensions matching the known extensions of index files).

Parameters
src source directory
dest destination directory
closeDirSrc if true, call close() method on source directory
Throws
IOException

public abstract IndexOutput createOutput (String name)

Creates a new, empty file in the directory with the given name. Returns a stream writing this file.

Throws
IOException

public abstract void deleteFile (String name)

Removes an existing file in the directory.

Throws
IOException

public abstract boolean fileExists (String name)

Returns true iff a file with the given name exists.

Throws
IOException

public abstract long fileLength (String name)

Returns the length of a file in the directory.

Throws
IOException

public abstract long fileModified (String name)

Returns the time the named file was last modified.

Throws
IOException

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.

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.

public abstract String[] listAll ()

Returns an array of strings, one for each file in the directory.

Throws
IOException

public Lock makeLock (String name)

Construct a Lock.

Parameters
name the name of the lock file

public IndexInput openInput (String name, int bufferSize)

Returns a stream reading an existing file, with the specified read buffer size. The particular Directory implementation may ignore the buffer size. Currently the only Directory implementations that respect this parameter are FSDirectory and org.apache.lucene.index.CompoundFileReader.

Throws
IOException

public abstract IndexInput openInput (String name)

Returns a stream reading an existing file.

Throws
IOException

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.

public void sync (String name)

Ensure that any writes to this file are moved to stable storage. Lucene uses this to properly commit changes to the index, to prevent a machine/OS crash from corrupting the index.

Throws
IOException

public String toString ()

public abstract void touchFile (String name)

Set the modified time of an existing file to now.

Throws
IOException

Protected Methods

protected final void ensureOpen ()

Throws
AlreadyClosedException if this Directory is closed