java.lang.Object
- org.apache.lucene.store.Directory

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

BaseDirectory, FilterDirectory, NRTCachingDirectory
```
public abstract class Directory
extends java.lang.Object
implements java.io.Closeable
```
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(org.apache.lucene.store.LockFactory).

Nested Class Summary

Nested Classes
Modifier and Type Class Description

class Directory.IndexInputSlicer
Allows to create one or more sliced IndexInput instances from a single file handle.

Constructor Summary

Constructors
Constructor Description

Directory()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`abstract void`	`clearLock(java.lang.String name)`	Attempt to clear (forcefully unlock and remove) the specified lock.
`abstract void`	`close()`	Closes the store.
`void`	`copy(Directory to, java.lang.String src, java.lang.String dest, IOContext context)`	Copies the file src to `Directory` to under the new file name dest.
`abstract IndexOutput`	`createOutput(java.lang.String name, IOContext context)`	Creates a new, empty file in the directory with the given name.
`Directory.IndexInputSlicer`	`createSlicer(java.lang.String name, IOContext context)`	Creates an `Directory.IndexInputSlicer` for the given file name.
`abstract void`	`deleteFile(java.lang.String name)`	Removes an existing file in the directory.
`abstract boolean`	`fileExists(java.lang.String name)`	Returns true iff a file with the given name exists.
`abstract long`	`fileLength(java.lang.String name)`	Returns the length of a file in the directory.
`abstract LockFactory`	`getLockFactory()`	Get the LockFactory that this Directory instance is using for its locking implementation.
`java.lang.String`	`getLockID()`	Return a string identifier that uniquely differentiates this Directory instance from other Directory instances.
`abstract java.lang.String[]`	`listAll()`	Returns an array of strings, one for each file in the directory.
`abstract Lock`	`makeLock(java.lang.String name)`	Construct a `Lock`.
`abstract IndexInput`	`openInput(java.lang.String name, IOContext context)`	Returns a stream reading an existing file, with the specified read buffer size.
`abstract void`	`setLockFactory(LockFactory lockFactory)`	Set the LockFactory that this Directory instance should use for its locking implementation.
`abstract void`	`sync(java.util.Collection<java.lang.String> names)`	Ensure that any writes to these files are moved to stable storage.
`java.lang.String`	`toString()`

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

- Constructor Detail
  - Directory
```
public Directory()
```
- Method Detail
  - listAll
```
public abstract java.lang.String[] listAll()
                                    throws java.io.IOException
```
    Returns an array of strings, one for each file in the directory.
    
    Throws:
    
    NoSuchDirectoryException - if the directory is not prepared for any write operations (such as createOutput(String, IOContext)).
    
    java.io.IOException - in case of other IO errors
  - fileExists
```
public abstract boolean fileExists(java.lang.String name)
                            throws java.io.IOException
```
    Returns true iff a file with the given name exists.
    
    Throws:
    
    java.io.IOException
  - deleteFile
```
public abstract void deleteFile(java.lang.String name)
                         throws java.io.IOException
```
    Removes an existing file in the directory.
    
    Throws:
    
    java.io.IOException
  - fileLength
```
public abstract long fileLength(java.lang.String name)
                         throws java.io.IOException
```
    Returns the length of a file in the directory. This method follows the following contract:
    
    Must throw FileNotFoundException if the file does not exist (not java.nio.file.NoSuchFileException of Java 7).
    Returns a value ≥0 if the file exists, which specifies its length.
    Parameters:
    
    name - the name of the file for which to return the length.
    
    Throws:
    
    java.io.IOException - if there was an IO error while retrieving the file's length.
  - createOutput
```
public abstract IndexOutput createOutput(java.lang.String name,
                                         IOContext context)
                                  throws java.io.IOException
```
    Creates a new, empty file in the directory with the given name. Returns a stream writing this file.
    
    Throws:
    
    java.io.IOException
  - sync
```
public abstract void sync(java.util.Collection<java.lang.String> names)
                   throws java.io.IOException
```
    Ensure that any writes to these files 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.
    
    NOTE: Clients may call this method for same files over and over again, so some impls might optimize for that. For other impls the operation can be a noop, for various reasons.
    
    Throws:
    
    java.io.IOException
  - openInput
```
public abstract IndexInput openInput(java.lang.String name,
                                     IOContext context)
                              throws java.io.IOException
```
    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 CompoundFileDirectory.
  - Must throw FileNotFoundException if the file does not exist (not java.nio.file.NoSuchFileException of Java 7).

Throws:: java.io.IOException

makeLock
```
public abstract Lock makeLock(java.lang.String name)
```
Construct a Lock.

Parameters:

name - the name of the lock file

clearLock
```
public abstract void clearLock(java.lang.String name)
                        throws java.io.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:

name - name of the lock to be cleared.

Throws:

java.io.IOException

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

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Throws:

java.io.IOException

setLockFactory
```
public abstract void setLockFactory(LockFactory lockFactory)
                             throws java.io.IOException
```
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.

Throws:

java.io.IOException

getLockFactory
```
public abstract 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 java.lang.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.

toString
```
public java.lang.String toString()
```
Overrides:

toString in class java.lang.Object

copy

public void copy(Directory to,
                 java.lang.String src,
                 java.lang.String dest,
                 IOContext context)
          throws java.io.IOException

Copies the file src to Directory to under the new file name dest.

If you want to copy the entire source directory to the destination one, you can do so like this:

 Directory to; // the directory to copy to
 for (String file : dir.listAll()) {
   dir.copy(to, file, newFile, IOContext.DEFAULT); // newFile can be either file, or a new name
 }

NOTE: this method does not check whether dest exist and will overwrite it if it does.

Throws:: java.io.IOException

createSlicer
```
public Directory.IndexInputSlicer createSlicer(java.lang.String name,
                                               IOContext context)
                                        throws java.io.IOException
```
Creates an Directory.IndexInputSlicer for the given file name. IndexInputSlicer allows other Directory implementations to efficiently open one or more sliced IndexInput instances from a single file handle. The underlying file handle is kept open until the Directory.IndexInputSlicer is closed.
Must throw FileNotFoundException if the file does not exist (not java.nio.file.NoSuchFileException of Java 7).

Throws:: java.io.IOException - if an IOException occurs

Class Directory

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Directory

Method Detail

listAll

fileExists

deleteFile

fileLength

createOutput

sync

openInput

makeLock

clearLock

close

setLockFactory

getLockFactory

getLockID

toString

copy

createSlicer