oracle.ias.cache
Class CacheLoader

java.lang.Object
  |
  +--oracle.ias.cache.CacheLoader

public abstract class CacheLoader

extends java.lang.Object

CacheLoader is an abstract class. Application should extend this class to handle the loading of objects into the cache. A cache loader can be registered for a region, a group or a specific object using CacheAccess object's define methods.

Since:

2.0.0

See Also:

CacheAccess.defineRegion, CacheAccess.defineGroup, CacheAccess.defineObject

Constructor Summary

CacheLoader()

Method Summary

Type	Method
protected java.io.File	createDiskObject(java.lang.Object handle) is called from the load method to create a disk object.
protected java.io.File	createDiskObject(java.lang.Object handle, Attributes attr) is called from the load method to create a disk object.
protected java.io.OutputStream	createStream(java.lang.Object handle) is called from the load method to create a streamAccessed object.
protected java.io.OutputStream	createStream(java.lang.Object handle, Attributes attr) is called from the load method to create a streamAccessed object.
protected CacheException	exceptionHandler(java.lang.String msg, java.lang.Exception ex) is called from the load method to convert any non CacheExceptions into CacheExceptions with the base exception set to the orginal exception.
protected java.lang.Object	getName(java.lang.Object handle) returns the name Object for the object being loaded.
protected java.lang.String	getRegion(java.lang.Object handle) returns the name of the region for the object being loaded.
abstract java.lang.Object	load(java.lang.Object handle, java.lang.Object argument) is an abstract method.
protected void	log(java.lang.String msg) The log method is called from the load method to record a message in the cache's log.
protected java.lang.Object	netSearch(java.lang.Object handle, int timeout) searchs other caches for the object to be loaded.
protected java.lang.Object	netSearch(java.lang.Object handle, int timeout, boolean useRemoteTtl) searchs other caches for the object to be loaded.
protected void	setAttributes(java.lang.Object handle, Attributes attr) sets the attributes of the object in the load method.

Methods inherited from class java.lang.Object

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

Constructor Detail

CacheLoader

public CacheLoader()

Method Detail

load

public abstract java.lang.Object load(java.lang.Object handle,
                                      java.lang.Object argument)
                               throws CacheException

is an abstract method. Applications should implement this method to customize the loading of cache object. This method is called by the caching service when the requested object is not in the cache.

Parameters:

handle - An internal handle object is passed in from cache service. It should only be used as the first parameter of the netSearch(handle, timeout) or setAttributes(handle, attributes) API.

argument - It is an argument object for load method passed in from customer code. This object is passed in as args either in get(String name, Object args), or get(String name, String group, Object args)

Returns:

In general, the object that is to be saved in the cache should be returned. If createStream has been called the OutputStream object returned by createStream should be returned. If createDiskObject is called the File object returned by createDiskObject should be returned.

Throws:

CacheException - if any error occurs.

Since:

2.0.0

See Also:

CacheAccess.get

netSearch

protected final java.lang.Object netSearch(java.lang.Object handle,
                                           int timeout)
                                    throws CacheException

searchs other caches for the object to be loaded. This method is called from the default load method and is available to be called by application overrides of the load method. This is a protected method so it is available only from the load method. If the search is successful, a reference to a local copy of the object is returned. If the object is not found an ObjectNotFoundException is thrown.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

timeout - The time to wait for the response in milliseconds.

Returns:

the requested object if found, otherwise a null.

Throws:

ObjectNotFoundException - if the object is not found or timeout.

Since:

2.0.0

netSearch

protected final java.lang.Object netSearch(java.lang.Object handle,
                                           int timeout,
                                           boolean useRemoteTtl)
                                    throws CacheException

searchs other caches for the object to be loaded. This method is called from the default load method and is available to be called by application overrides of the load method. If the useRemoteTtl parameter is true, the time to live interval or idle time interval that was set at the remote site will be used locally overwriting the attribute that is currently set. NetSearch is a protected method so it is available only from the load method. If the search is successful, a reference to a local copy of the object is returned. If the object is not found an ObjectNotFoundException is thrown.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

timeout - The time to wait for the response in milliseconds.

useRemoteTtl - if true the idletime/ttlInterval from the remote cache are used as the local values

Returns:

the requested object if found, otherwise a null.

Throws:

ObjectNotFoundException - if the object is not found or timeout.

Since:

2.0.0

setAttributes

protected final void setAttributes(java.lang.Object handle,
                                   Attributes attr)
                            throws CacheException

sets the attributes of the object in the load method. This method is available to be called by application overrides of the load method. This is a protected method so it is available only from the load method.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

attr - The set of attributes to associate with the object

Throws:

CacheException - if a error occurs

Since:

2.0.0

getName

protected final java.lang.Object getName(java.lang.Object handle)

returns the name Object for the object being loaded. This method is available to be called by application overrides of the load method. This is a protected method so it is available only from the load method.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

Returns:

The name Object for the object being loaded.

Since:

2.0.0

getRegion

protected final java.lang.String getRegion(java.lang.Object handle)

returns the name of the region for the object being loaded. This method is available to be called by application overrides of the load method. This is a protected method so it is available only from the load method.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

Returns:

The name Object for the object being loaded.

Since:

2.0.0

createStream

protected final java.io.OutputStream createStream(java.lang.Object handle,
                                                  Attributes attr)
                                           throws ObjectExistsException,
                                                  DiskCacheException,
                                                  CacheException

is called from the load method to create a streamAccessed object. The OutputStream object returned is used to load the object into the cache. When using a StreamAccess object the attributes for the object should be set on the createStream call rather than with the setAttributes method. This ensure that the file will be created correctly with relationship to the DISTRIBUTE flag. If the object is distributed and is being loaded or has been loaded by another cache an ObjectExistException is thrown. This exception should be thrown by the load method. The cache will handle the exception and return the loaded object to the application.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

attr - The set of attributes to associate with the object

Returns:

An OutputStream to load the object into the cache.

Throws:

CacheException - if a error occurs

ObjectExistsException - if the object is being or has already been loaded by another cache

Since:

2.0.0

createStream

protected final java.io.OutputStream createStream(java.lang.Object handle)
                                           throws ObjectExistsException,
                                                  DiskCacheException,
                                                  CacheException,
                                                  java.io.IOException

is called from the load method to create a streamAccessed object. The OutputStream object returned is used to load the object into the cache. When using a StreamAccess object the attributes for the object should be set on the createStream call rather than with the setAttributes method. This ensure that the file will be created correctly with relationship to the DISTRIBUTE flag. If the object is distributed and is being loaded or has been loaded by another cache an ObjectExistException is thrown. This exception should be thrown by the load method. The cache will handle the exception and return the loaded object to the application.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

Returns:

An OutputStream to load the object into the cache.

Throws:

ObjectExistsException - if the object is being or has already been loaded by another cache

Since:

2.0.0

createDiskObject

protected final java.io.File createDiskObject(java.lang.Object handle,
                                              Attributes attr)
                                       throws ObjectExistsException,
                                              DiskCacheException,
                                              CacheException,
                                              java.io.IOException

is called from the load method to create a disk object. The File object returned is used to load the object into the cache. When using a Disk object the attributes for the object should be set on the createDiskObject call rather than with the setAttributes method. This insure that the file will be created correctly with relationship to the DISTRIBUTE flag. If the object is distributed and is being loaded or has been loaded by another cache an ObjectExistException is thrown. This exception should be thrown by the load method. The cache will handle the exception and return the loaded object to the application.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

attr - The set of attributes to associate with the object

Returns:

An OutputStream to load the object into the cache.

Throws:

CacheException - if a error occurs

ObjectExistsException - if the object is being or has already been loaded by another cache

Since:

2.0.0

createDiskObject

protected final java.io.File createDiskObject(java.lang.Object handle)
                                       throws ObjectExistsException,
                                              DiskCacheException,
                                              CacheException,
                                              java.io.IOException

is called from the load method to create a disk object. The File object returned is used to load the object into the cache. When using a Disk object the attributes for the object should be set on the createDiskObject call rather than with the setAttributes method. This insure that the file will be created correctly with relationship to the DISTRIBUTE flag. If the object is distributed and is being loaded or has been loaded by another cache an ObjectExistException is thrown. This exception should be thrown by the load method. The cache will handle the exception and return the loaded object to the application.

Parameters:

handle - An internal cache handle object, it is passed in as the first parameter in load(Object handle, Object argument().

Returns:

An OutputStream to load the object into the cache.

Throws:

ObjectExistsException - if the object is being or has already been loaded by another cache

Since:

2.0.0

exceptionHandler

protected final CacheException exceptionHandler(java.lang.String msg,
                                                java.lang.Exception ex)

is called from the load method to convert any non CacheExceptions into CacheExceptions with the base exception set to the orginal exception. This allows the load method to only throw CacheExceptions without loosing important information. The exception will also be logged (assuming that logging is configured and the logging severity is set sufficiently high). For all CacheExceptions, if CacheException.printStackTrace() is called and there is a base exception, the stack for the base exception will be printed.

Parameters:

msg - the message to be included with the exception

ex - the original exception

Returns:

A CacheException

Since:

2.0.0

log

protected final void log(java.lang.String msg)

The log method is called from the load method to record a message in the cache's log. How and where the logging occurs is dependent of the configuration of the logger in the cache.

Parameters:

msg - the message to be logged

Since:

2.0.0