wt.pom
Class StatementCache

java.lang.Object
  java.util.AbstractMap
      wt.util.Cache
          wt.pom.StatementCache

All Implemented Interfaces:

Map

public class StatementCache

extends Cache

A fixed size cache of java.sql.Statement objects indexed by SQL string.

See Also:

Cache

Nested Class Summary

Nested classes inherited from class wt.util.Cache

Cache.CacheEntry

Nested classes inherited from class java.util.AbstractMap

Nested classes inherited from class java.util.Map

Map.Entry

Field Summary

private int	count
private int	reuseLimit
private static String	versionID

Fields inherited from class wt.util.Cache

agedOut, cacheSize, hashCodes, hits, keys, misses, modCount, tableSize, values

Constructor Summary

StatementCache(int size, int reuse_limit)
Construct a new StatementCache

Method Summary

void	clear() Empty the cache.
void	free(Object key, Object stmt) Free an entry in the cache for reuse.
Object	get(Object key) Get an entry from the cache.
protected void	overflow(Object key, Object value) Called when an entry is being aged out of the cache.
Object	put(Object key, Object value) Put an entry in the cache.
Object	remove(Object key) Remove an entry in the cache.

Methods inherited from class wt.util.Cache

containsKey, containsValue, createEntry, entries, entrySet, find, getAndRemove, getAndReplace, getKeys, keySet, link, print, size, toString, touch

Methods inherited from class java.util.AbstractMap

clone, equals, hashCode, isEmpty, putAll, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

versionID

private static final String versionID

See Also:

Constant Field Values

reuseLimit

private int reuseLimit

count

private int count

Constructor Detail

StatementCache

public StatementCache(int size,
                      int reuse_limit)

Construct a new StatementCache

Parameters:

size - number of entries in the cache

reuse_limit - limit to number of times a cached statement is used (0 = infinite)

Method Detail

get

public Object get(Object key)

Get an entry from the cache. If an entry is found, it is considered busy until later freed to prevent it from being used recursively or closed by cache overflow.

Specified by:

get in interface Map

Overrides:

get in class Cache

Parameters:

key - the entry key

Returns:

the cached object or null if not found

put

public Object put(Object key,
                  Object value)

Put an entry in the cache. If an entry for the given key already exists, the previous value is discarded. This entry is considered the most recently used.

Specified by:

put in interface Map

Overrides:

put in class Cache

Parameters:

key - the entry key

value - the value to associate with the given key

Returns:

The previous value that mapped to the key, or null if there was no previous value

remove

public Object remove(Object key)

Remove an entry in the cache.

Specified by:

remove in interface Map

Overrides:

remove in class Cache

Parameters:

key - the entry key

free

public void free(Object key,
                 Object stmt)

Free an entry in the cache for reuse.

Parameters:

key - the entry key

stmt - the statement

Returns:

the cached object or null if not found

clear

public void clear()

Empty the cache. Closes any statements in the cache, ignoring any exceptions.

Specified by:

clear in interface Map

Overrides:

clear in class Cache

See Also:

Cache

overflow

protected void overflow(Object key,
                        Object value)

Called when an entry is being aged out of the cache. Closes the statement, ignoring any exceptions.

Overrides:

overflow in class Cache

Parameters:

key - the entry key

value - the entry value