Package org.nuxeo.common.file

Class LRUFileCache

java.lang.Object

org.nuxeo.common.file.LRUFileCache

All Implemented Interfaces:

FileCache

public class LRUFileCache
extends Object
implements FileCache

A LRU cache of Files with maximum filesystem size.

Cache entries that are old enough and whose size makes the cache bigger than its maximum size are deleted.

The cache keys are restricted to a subset of ASCII: letters, digits and dashes. Usually a MD5 or SHA1 hash is used.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	LRUFileCache.PathInfo
protected static class	LRUFileCache.RegularFileFilter	Filter keeping regular files that aren't temporary.

Field Summary

Fields

Modifier and Type	Field	Description
static long	CLEAR_OLD_ENTRIES_INTERVAL_MILLIS_DEFAULT
protected long	clearOldEntriesIntervalMillis
protected long	clearOldEntriesLast
protected Lock	clearOldEntriesLock
protected Path	dir
protected long	maxCount
protected long	maxSize
protected long	minAgeMillis
static Pattern	SIMPLE_ASCII	Allowed key pattern, used as file path.

Constructor Summary

Constructors

Constructor	Description
LRUFileCache(File dir, long maxSize, long maxCount, long minAge)	Constructs a cache in the given directory with the given maximum size (in bytes).

Method Summary

Modifier and Type	Method	Description
protected void	checkKey(String key)
void	clear()	Clears the cache.
protected void	clearOldEntries()	Clears cache entries if they are old enough and their size makes the cache bigger than its maximum size.
protected void	doClearOldEntries()
File	getFile(String key)	Gets a file from the cache.
int	getNumberOfItems()	Gets the number of items in the cache.
long	getSize()	Gets the size of the cache, in bytes.
File	getTempFile()	Creates a temporary file.
File	putFile(String key, File file)	Puts a file in the cache.
File	putFile(String key, InputStream in)	Puts a file in the cache.
protected void	recordAccess(Path path)	Records access to a file by changing its modification time.
void	setClearOldEntriesIntervalMillis(long millis)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SIMPLE_ASCII

public static final Pattern SIMPLE_ASCII

Allowed key pattern, used as file path.

CLEAR_OLD_ENTRIES_INTERVAL_MILLIS_DEFAULT

public static final long CLEAR_OLD_ENTRIES_INTERVAL_MILLIS_DEFAULT

See Also:

Constant Field Values

clearOldEntriesIntervalMillis

protected long clearOldEntriesIntervalMillis

dir

protected final Path dir

maxSize

protected final long maxSize

maxCount

protected final long maxCount

minAgeMillis

protected final long minAgeMillis

clearOldEntriesLock

protected Lock clearOldEntriesLock

clearOldEntriesLast

protected long clearOldEntriesLast

Constructor Detail

LRUFileCache

public LRUFileCache(File dir,
                    long maxSize,
                    long maxCount,
                    long minAge)

Constructs a cache in the given directory with the given maximum size (in bytes).

Parameters:

dir - the directory to use to store cached files

maxSize - the maximum size of the cache (in bytes)

maxCount - the maximum number of files in the cache

minAge - the minimum age of a file in the cache to be eligible for removal (in seconds)

Method Detail

setClearOldEntriesIntervalMillis

public void setClearOldEntriesIntervalMillis(long millis)

getSize

public long getSize()

Description copied from interface: FileCache

Gets the size of the cache, in bytes.

Specified by:

getSize in interface FileCache

getNumberOfItems

public int getNumberOfItems()

Description copied from interface: FileCache

Gets the number of items in the cache.

Specified by:

getNumberOfItems in interface FileCache

clear

public void clear()

Description copied from interface: FileCache

Clears the cache.

Files will not be deleted from the filesystm while the returned file objects are still referenced.

Specified by:

clear in interface FileCache

clearOldEntries

protected void clearOldEntries()

Clears cache entries if they are old enough and their size makes the cache bigger than its maximum size.

doClearOldEntries

protected void doClearOldEntries()

getTempFile

public File getTempFile()
                 throws IOException

Description copied from interface: FileCache

Creates a temporary file.

Specified by:

getTempFile in interface FileCache

Throws:

IOException

checkKey

protected void checkKey(String key)
                 throws IllegalArgumentException

Throws:

IllegalArgumentException

putFile

public File putFile(String key,
                    InputStream in)
             throws IOException

Puts a file in the cache.

The key is used as a file name in the directory cache.

Specified by:

putFile in interface FileCache

Parameters:

key - the cache key

in - the input stream to cache (closed afterwards)

Returns:

the cached file

Throws:

IOException

putFile

public File putFile(String key,
                    File file)
             throws IllegalArgumentException,
                    IOException

Puts a file in the cache.

The file must have been created through FileCache.getTempFile(). The file is "given" to this method, who will delete it or rename it.

The key is used as a file name in the directory cache.

Specified by:

putFile in interface FileCache

Parameters:

key - the cache key

file - the file to cache

Returns:

the cached file

Throws:

IllegalArgumentException - if the key is illegal

IOException

getFile

public File getFile(String key)

Description copied from interface: FileCache

Gets a file from the cache.

A returned file will never be deleted from the filesystem while the returned file object is still referenced, although it may be purged from the cache.

Specified by:

getFile in interface FileCache

Parameters:

key - the cache key

Returns:

the cached file, or null if absent

recordAccess

protected void recordAccess(Path path)

Records access to a file by changing its modification time.