org.aoju.bus.http.cache

Class DiskLruCache

java.lang.Object

org.aoju.bus.http.cache.DiskLruCache

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public final class DiskLruCache
extends Object
implements Closeable, Flushable

A cache that uses a bounded amount of space on a filesystem. Each cache entry has a string key and a fixed number of values. Each key must match the regex [a-z0-9_-]{1,64}. Values are byte sequences, accessible as streams or files. Each value must be between 0 and Integer.MAX_VALUE bytes in length.

The cache stores its data in a directory on the filesystem. This directory must be exclusive to the cache; the cache may delete or overwrite files from its directory. It is an error for multiple processes to use the same cache directory at the same time.

This cache limits the number of bytes that it will store on the filesystem. When the number of stored bytes exceeds the limit, the cache will remove entries in the background until the limit is satisfied. The limit is not strict: the cache may temporarily exceed it while waiting for files to be deleted. The limit does not include filesystem overhead or the cache journal so space-sensitive applications should set a conservative limit.

Clients call edit(java.lang.String) to create or update the values of an entry. An entry may have only first editor at first time; if a value is not available to be edited then edit(java.lang.String) will return null.

• When an entry is being created it is necessary to supply a full set of values; the empty value should be used as a placeholder if necessary.
• When an entry is being edited, it is not necessary to supply data for every value; values default to their previous value.

Every edit(java.lang.String) call must be matched by a call to DiskLruCache.Editor.commit() or DiskLruCache.Editor.abort(). Committing is atomic: a read observes the full set of values as they were before or after the commit, but never a mix of values.

Clients call get(java.lang.String) to read a snapshot of an entry. The read will observe the value at the time that get(java.lang.String) was called. Updates and removals after the call do not impact ongoing reads.

This class is tolerant of some I/O errors. If files are missing from the filesystem, the corresponding entries will be dropped from the cache. If an error occurs while writing a cache value, the edit will fail silently. Callers should handle other problems by catching IOException and responding appropriately.

Since:

JDK 1.8

Version:

3.6.5

Author:

Kimi Liu

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	DiskLruCache.Editor Edits the values for an entry.
class	DiskLruCache.Snapshot

Method Summary

Modifier and Type	Method and Description
void	close()
static DiskLruCache	create(FileSystem fileSystem, File directory, int appVersion, int valueCount, long maxSize)
void	delete()
DiskLruCache.Editor	edit(String key)
void	evictAll()
void	flush()
DiskLruCache.Snapshot	get(String key)
File	getDirectory()
long	getMaxSize()
void	initialize()
boolean	isClosed()
boolean	remove(String key)
void	setMaxSize(long maxSize)
long	size()
Iterator<DiskLruCache.Snapshot>	snapshots()

Methods inherited from class java.lang.Object

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

Method Detail

create

public static DiskLruCache create(FileSystem fileSystem,
                                  File directory,
                                  int appVersion,
                                  int valueCount,
                                  long maxSize)

initialize

public void initialize()
                throws IOException

Throws:

IOException

get

public DiskLruCache.Snapshot get(String key)
                          throws IOException

Throws:

IOException

edit

public DiskLruCache.Editor edit(String key)
                         throws IOException

Throws:

IOException

getDirectory

public File getDirectory()

getMaxSize

public long getMaxSize()

setMaxSize

public void setMaxSize(long maxSize)

size

public long size()
          throws IOException

Throws:

IOException

remove

public boolean remove(String key)
               throws IOException

Throws:

IOException

isClosed

public boolean isClosed()

flush

public void flush()
           throws IOException

Specified by:

flush in interface Flushable

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

delete

public void delete()
            throws IOException

Throws:

IOException

evictAll

public void evictAll()
              throws IOException

Throws:

IOException

snapshots

public Iterator<DiskLruCache.Snapshot> snapshots()
                                          throws IOException

Throws:

IOException