apache::geode::client::CacheLoader Class Reference

An application plug-in that can be installed on a region. More...

Public Member Functions
virtual void	close (Region &rp)
	Called when the region containing this callback is destroyed, when the cache is closed. More...
virtual std::shared_ptr< Cacheable >	load (Region &rp, const std::shared_ptr< CacheableKey > &key, const std::shared_ptr< Serializable > &aCallbackArgument)=0
	Loads a value. More...

Detailed Description

An application plug-in that can be installed on a region.

Loaders facilitate loading of data into the cache. When an application does a lookup for a key in a region and it does not exist, the system checks to see if any loaders are available for the region in the system and invokes them to get the value for the key into the cache. Allows data to be loaded from a 3rd party data source and placed into the region When Region::get is called for a region entry that has a nullptr value, the CacheLoader::load method of the region's cache loader is invoked. The load method creates the value for the desired key by performing an operation such as a database query.

See also

RegionAttributesFactory::setCacheLoader

RegionAttributes::getCacheLoader

Member Function Documentation

close()

virtual void apache::geode::client::CacheLoader::close ( Region &  rp )

virtual

Called when the region containing this callback is destroyed, when the cache is closed.

Implementations should clean up any external resources, such as database connections. Any runtime exceptions this method throws will be logged.

It is possible for this method to be called multiple times on a single callback instance, so implementations must be tolerant of this.

Parameters

rp	the region pointer

See also

Cache::close

Region::destroyRegion

load()

virtual std::shared_ptr<Cacheable> apache::geode::client::CacheLoader::load ( Region &  rp, const std::shared_ptr< CacheableKey > &  key, const std::shared_ptr< Serializable > &  aCallbackArgument  )

pure virtual

Loads a value.

Application writers should implement this method to customize the loading of a value. This method is called by the caching service when the requested value is not in the cache. Any exception thrown by this method is propagated back to and thrown by the invocation of Region::get that triggered this load.

Parameters

rp	a Region Pointer for which this is called.
key	the key for the cacheable
helper	any related user data, or nullptr

Returns

the value supplied for this key, or nullptr if no value can be supplied.

See also

Region::get .