Module com.semanticcms.core.servlet

Package com.semanticcms.core.servlet

Class Cache

java.lang.Object

com.semanticcms.core.servlet.Cache

public abstract class Cache
extends Object

A caching cache, whether shared between requests or used within the scope of a single request.

The thread safety will be the minimum needed for the expected usage.

1. Thread safe for caches shared between requests.
2. Thread safe for caches used in requests that may use concurrent subrequests.
3. Not thread safe for per-request, no-subrequest caches. (in this case it's much like request attributes).

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Cache.Callable<V,Ex extends Exception>	Constrains allowed exception type.

Field Summary

Fields

Modifier and Type	Field	Description
protected static final boolean	VERIFY_CACHE_PARENT_CHILD_RELATIONSHIPS	Enables the page parent-child relationships verification.

Constructor Summary

Constructors

Constructor	Description
Cache()

Method Summary

Modifier and Type	Method	Description
abstract Object	getAttribute(String key)	Gets a cache attribute or null if not in cache.
<V> V	getAttribute(String key, Class<V> clazz)	Gets a cache attribute or null if not in cache.
abstract <V, Ex extends Exception> V	getAttribute(String key, Class<V> clazz, Cache.Callable<? extends V,Ex> callable)	Atomically checks the cache then calls the callable and adds.
abstract <K, V> Map<K,V>	newMap()	Creates a new map that is suitable for the expected thread safety requirements.
abstract <K, V> Map<K,V>	newMap(int size)	Creates a new map that is suitable for the expected thread safety requirements.
abstract void	removeAttribute(String key)	Removes a cache attribute.
abstract void	setAttribute(String key, Object value)	Sets a cache attribute.

Methods inherited from class java.lang.Object

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

Field Details

VERIFY_CACHE_PARENT_CHILD_RELATIONSHIPS

protected static final boolean VERIFY_CACHE_PARENT_CHILD_RELATIONSHIPS

Enables the page parent-child relationships verification.

This does not measurably affect performance; just leave it on.

See Also:

• Constant Field Values

Constructor Details

Cache

public Cache()

Method Details

newMap

public abstract <K,
V> Map<K,V> newMap()

Creates a new map that is suitable for the expected thread safety requirements. This map will itself be consistent with the thread safety guarantees of this cache overall.

newMap

public abstract <K,
V> Map<K,V> newMap(int size)

Creates a new map that is suitable for the expected thread safety requirements. This map will itself be consistent with the thread safety guarantees of this cache overall.

Parameters:

size - the number of elements the map can hold before internal resizing. this is the actual size, no need to consider load factor or other nonsense.

setAttribute

public abstract void setAttribute(String key,
 Object value)

Sets a cache attribute.

See Also:

• Setting to a null value is equivalent to calling removeAttribute.

getAttribute

public abstract Object getAttribute(String key)

Gets a cache attribute or null if not in cache.

getAttribute

public <V> V getAttribute(String key,
 Class<V> clazz)

Gets a cache attribute or null if not in cache. The attribute is cast to the provided type.

getAttribute

public abstract <V,
Ex extends Exception> V getAttribute(String key,
 Class<V> clazz,
 Cache.Callable<? extends V,Ex> callable)
                                                  throws Ex

Atomically checks the cache then calls the callable and adds. Note: It is possible the callable might be called and not used. If clean-up of unused callable is necessary, synchronize externally and use regular getAttribute/setAttribute in sequence.

Type Parameters:

Ex - An arbitrary exception type that may be thrown

Throws:

Ex

removeAttribute

public abstract void removeAttribute(String key)

Removes a cache attribute.