Package com.squareup.okhttp.internal

Class DiskLruCache

java.lang.Object
com.squareup.okhttp.internal.DiskLruCache
All Implemented Interfaces:
Closeable, AutoCloseable
public final class DiskLruCache
extends Object
implements Closeable
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 one editor at one 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.

  • Nested Class Summary

    Nested Classes
    Modifier and Type Class Description
    class  DiskLruCache.Editor
    Edits the values for an entry.
    class  DiskLruCache.Snapshot
    A snapshot of the values for an entry.

  • Method Summary

    Modifier and Type Method Description
    void close()
    Closes this cache.
    void delete()
    Closes the cache and deletes all of its stored values.
    DiskLruCache.Editor edit​(String key)
    Returns an editor for the entry named key, or null if another edit is in progress.
    void flush()
    Force buffered operations to the filesystem.
    DiskLruCache.Snapshot get​(String key)
    Returns a snapshot of the entry named key, or null if it doesn't exist is not currently readable.
    File getDirectory()
    Returns the directory where this cache stores its data.
    long getMaxSize()
    Returns the maximum number of bytes that this cache should use to store its data.
    boolean isClosed()
    Returns true if this cache has been closed.
    static DiskLruCache open​(File directory, int appVersion, int valueCount, long maxSize)
    Opens the cache in directory, creating a cache if none exists there.
    boolean remove​(String key)
    Drops the entry for key if it exists and can be removed.
    void setMaxSize​(long maxSize)
    Changes the maximum number of bytes the cache can store and queues a job to trim the existing store, if necessary.
    long size()
    Returns the number of bytes currently being used to store the values in this cache.

    Methods inherited from class java.lang.Object

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

  • Method Details

    • open

      public static DiskLruCache open​(File directory, int appVersion, int valueCount, long maxSize) throws IOException
      Opens the cache in directory, creating a cache if none exists there.
      Parameters:
      directory - a writable directory
      valueCount - the number of values per cache entry. Must be positive.
      maxSize - the maximum number of bytes this cache should use to store
      Throws:
      IOException - if reading or writing the cache directory fails

    • get

      public DiskLruCache.Snapshot get​(String key) throws IOException
      Returns a snapshot of the entry named key, or null if it doesn't exist is not currently readable. If a value is returned, it is moved to the head of the LRU queue.
      Throws:
      IOException

    • edit

      public DiskLruCache.Editor edit​(String key) throws IOException
      Returns an editor for the entry named key, or null if another edit is in progress.
      Throws:
      IOException

    • getDirectory

      public File getDirectory()
      Returns the directory where this cache stores its data.

    • getMaxSize

      public long getMaxSize()
      Returns the maximum number of bytes that this cache should use to store its data.

    • setMaxSize

      public void setMaxSize​(long maxSize)
      Changes the maximum number of bytes the cache can store and queues a job to trim the existing store, if necessary.

    • size

      public long size()
      Returns the number of bytes currently being used to store the values in this cache. This may be greater than the max size if a background deletion is pending.

    • remove

      public boolean remove​(String key) throws IOException
      Drops the entry for key if it exists and can be removed. Entries actively being edited cannot be removed.
      Returns:
      true if an entry was removed.
      Throws:
      IOException

    • isClosed

      public boolean isClosed()
      Returns true if this cache has been closed.

    • flush

      public void flush() throws IOException
      Force buffered operations to the filesystem.
      Throws:
      IOException

    • close

      public void close() throws IOException
      Closes this cache. Stored values will remain on the filesystem.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException

    • delete

      public void delete() throws IOException
      Closes the cache and deletes all of its stored values. This will delete all files in the cache directory including files that weren't created by the cache.
      Throws:
      IOException