er.extensions.foundation
Class ERXLazyValue<T>

java.lang.Object
  er.extensions.foundation.ERXLazyValue<T>

Type Parameters:

T - the type of the lazy value

public class ERXLazyValue<T>
extends java.lang.Object

ERXLazyValue provides a way to model lazy-loaded values that invalidate with different methods. This is very useful for storing expensive values that are returned from bound component methods as well as values that are cached that are influenced by different areas of a single page (i.e. ajax operations on one part of the page that need to invalidate a cache on another part of the page).

Author:

mschrag

Nested Class Summary

static class	ERXLazyValue.AjaxPageUserInfoCacheKeyInvalidator AjaxPageUserInfoCacheKeyInvalidator triggers a cache invalidation when the value of the specified key changes in the ERXResponseRewriter's ajaxPageUserInfo.
static class	ERXLazyValue.AlwaysInvalidator Returns true from shouldInvalidate, causing the cache to always refresh.
static class	ERXLazyValue.CacheKeyInvalidator The base class for any invalidator that is triggered by the change in a cache key.
static class	ERXLazyValue.ConstantSource<T> ConstantSource provides a Source implementation on top of a fixed value.
static interface	ERXLazyValue.Invalidator Invalidator provides an mechanism for selectively invalidating the cached lazy value.
static class	ERXLazyValue.KVCSource<T> KVCSource provides a wrapper around a KVC binding, which is very useful in components.
static class	ERXLazyValue.MutableCacheKeyInvalidator The base class for any invalidator that is triggered by the change in a cache key with support for changing the value.
static class	ERXLazyValue.NeverInvalidator Returns false from shouldInvalidate, causing the cache to never refresh.
static class	ERXLazyValue.PageUserInfoCacheKeyInvalidator PageUserInfoCacheKeyInvalidator triggers a cache invalidation when the value of the specified key changes in the ERXResponseRewriter's pageUserInfo.
static interface	ERXLazyValue.Source<T> A source provides the undelying value (which is usually uncached) to a lazy value.
static class	ERXLazyValue.ThreadStorageCacheKeyInvalidator ThreadStorageCacheKeyInvalidator triggers a cache invalidation when the value of the specified key changes in the ERXThreadStorage.
static class	ERXLazyValue.TimedInvalidator TimedInvalidator specifies that the cached value should be invalidated after a specified duration.

Field Summary

static org.apache.log4j.Logger

log

Constructor Summary

ERXLazyValue(ERXLazyValue.Source<T> dataSource)
Constructs a new ERXLazyValue with a data source and a NeverInvalidator, which behaves like a "once" lazy value.

ERXLazyValue(ERXLazyValue.Source<T> dataSource, ERXLazyValue.Invalidator invalidator)
Constructs a new ERXLazyValue with a data source and an invalidator.

ERXLazyValue(java.lang.Object target, java.lang.String keyPath)
Constructs a new ERXLazyValue with a shortcut for a KVCSource and a NeverInvalidator, which behaves like a "once" lazy value.

ERXLazyValue(java.lang.Object target, java.lang.String keyPath, ERXLazyValue.Invalidator invalidator)
Constructs a new ERXLazyValue with a shortcut for a KVCSource and an invalidator.

Method Summary

void	invalidate() Forecfully invalidates the lazy value, regardless of the state of the invalidator.
void	setValue(T value) Sets the backging value for this lazy value, which will always call through to the underlying data source.
T	value() Returns the backing value for this lazy value, which will only sometimes trigger a call through to the data source.

Methods inherited from class java.lang.Object

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

Field Detail

log

public static org.apache.log4j.Logger log

Constructor Detail

ERXLazyValue

public ERXLazyValue(ERXLazyValue.Source<T> dataSource)

Constructs a new ERXLazyValue with a data source and a NeverInvalidator, which behaves like a "once" lazy value.

Parameters:

dataSource - the data source for the lazy value

ERXLazyValue

public ERXLazyValue(java.lang.Object target,
                    java.lang.String keyPath)

Constructs a new ERXLazyValue with a shortcut for a KVCSource and a NeverInvalidator, which behaves like a "once" lazy value.

Parameters:

target - the target of the KVCSource

keyPath - the keypath of the KVCSource

ERXLazyValue

public ERXLazyValue(java.lang.Object target,
                    java.lang.String keyPath,
                    ERXLazyValue.Invalidator invalidator)

Constructs a new ERXLazyValue with a shortcut for a KVCSource and an invalidator.

Parameters:

target - the target of the KVCSource

keyPath - the keypath of the KVCSource

invalidator - the invalidator to use

ERXLazyValue

public ERXLazyValue(ERXLazyValue.Source<T> dataSource,
                    ERXLazyValue.Invalidator invalidator)

Constructs a new ERXLazyValue with a data source and an invalidator.

Parameters:

dataSource - the data source for the lazy value

invalidator - the invalidator to use

Method Detail

invalidate

public void invalidate()

Forecfully invalidates the lazy value, regardless of the state of the invalidator.

value

public T value()

Returns the backing value for this lazy value, which will only sometimes trigger a call through to the data source.

Returns:

the backing value

setValue

public void setValue(T value)

Sets the backging value for this lazy value, which will always call through to the underlying data source. This will also cache the new value and notify the invalidator of a new fetched value (acting just like if value() was called on an invalidated cache).

Parameters:

value - the new value