de.umass.lastfm.cache
Class DatabaseCache

java.lang.Object
  de.umass.lastfm.cache.Cache
      de.umass.lastfm.cache.DatabaseCache

public class DatabaseCache
extends Cache

Generic class for caching into a database. It's constructor takes a Connection instance, which must be opened and closed by the client. SQL code used in this class should work with all common databases (which support varchar, timestamp and longvarchar datatypes).
For more specialized versions of this class for different databases one may extend this class and override methods as needed.

Author:

Janni Kovacs

Field Summary

protected java.sql.Connection	conn
protected static java.lang.String	TABLE_NAME

Constructor Summary

DatabaseCache(java.sql.Connection connection)

Method Summary

void	clear() Clears the cache by effectively removing all cached data.
boolean	contains(java.lang.String cacheEntryName) Checks if the cache contains an entry with the given name.
protected void	createTable()
boolean	isExpired(java.lang.String cacheEntryName) Checks if the specified entry is expired.
java.io.InputStream	load(java.lang.String cacheEntryName) Loads the specified entry from the cache and returns an InputStream to be read from.
void	remove(java.lang.String cacheEntryName) Removes the specified entry from the cache if available.
void	store(java.lang.String cacheEntryName, java.io.InputStream inputStream, long expirationDate) Stores a request in the cache.

Methods inherited from class de.umass.lastfm.cache.Cache

createCacheEntryName, getExpirationPolicy, setExpirationPolicy, setHashCacheEntryNames

Methods inherited from class java.lang.Object

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

Field Detail

TABLE_NAME

protected static final java.lang.String TABLE_NAME

See Also:

Constant Field Values

conn

protected java.sql.Connection conn

Constructor Detail

DatabaseCache

public DatabaseCache(java.sql.Connection connection)
              throws java.sql.SQLException

Throws:

java.sql.SQLException

Method Detail

createTable

protected void createTable()
                    throws java.sql.SQLException

Throws:

java.sql.SQLException

contains

public boolean contains(java.lang.String cacheEntryName)

Description copied from class: Cache

Checks if the cache contains an entry with the given name.

Specified by:

contains in class Cache

Parameters:

cacheEntryName - An entry name

Returns:

true if the cache contains this entry

load

public java.io.InputStream load(java.lang.String cacheEntryName)

Description copied from class: Cache

Loads the specified entry from the cache and returns an InputStream to be read from. Returns null if the cache does not contain the specified cacheEntryName.

Specified by:

load in class Cache

Parameters:

cacheEntryName - An entry name

Returns:

an InputStream or null

remove

public void remove(java.lang.String cacheEntryName)

Description copied from class: Cache

Removes the specified entry from the cache if available. Does nothing if no such entry is available.

Specified by:

remove in class Cache

Parameters:

cacheEntryName - An entry name

store

public void store(java.lang.String cacheEntryName,
                  java.io.InputStream inputStream,
                  long expirationDate)

Description copied from class: Cache

Stores a request in the cache.

Specified by:

store in class Cache

Parameters:

cacheEntryName - The entry name to be stored to

inputStream - An InputStream containing the data to be cached

expirationDate - The date of expiration represented in milliseconds since 1.1.1970

isExpired

public boolean isExpired(java.lang.String cacheEntryName)

Description copied from class: Cache

Checks if the specified entry is expired.

Specified by:

isExpired in class Cache

Parameters:

cacheEntryName - An entry name

Returns:

true if the entry is expired

clear

public void clear()

Description copied from class: Cache

Clears the cache by effectively removing all cached data.

Specified by:

clear in class Cache