org.jboss.cache.loader

Class ChainingCacheLoader

java.lang.Object

org.jboss.cache.loader.AbstractCacheLoader

org.jboss.cache.loader.ChainingCacheLoader

All Implemented Interfaces:

Lifecycle, CacheLoader

public class ChainingCacheLoader
extends AbstractCacheLoader

This decorator is used whenever more than one cache loader is configured. READ operations are directed to each of the cache loaders (in the order which they were configured) until a non-null (or non-empty in the case of retrieving collection objects) result is achieved.

WRITE operations are propagated to ALL registered cacheloaders that specified set ignoreModifications to false.

Author:

Manik Surtani (manik AT jboss DOT org)

Field Summary

Fields inherited from class org.jboss.cache.loader.AbstractCacheLoader

buddyFqnTransformer, cache, regionManager, transactions

Constructor Summary

Constructors

Constructor and Description
ChainingCacheLoader()

Method Summary

Methods

Modifier and Type	Method and Description
void	addCacheLoader(CacheLoader l, CacheLoaderConfig.IndividualCacheLoaderConfig cfg) Adds a cache loader to the chain (always added at the end of the chain)
void	commit(Object tx) Commit the transaction.
void	create() Creates individual cache loaders.
void	destroy()
boolean	exists(Fqn name) Checks whether the CacheLoader has a node with Fqn
Map	get(Fqn name) Returns all keys and values from the persistent store, given a fully qualified name
List<CacheLoader>	getCacheLoaders() Returns a List of individual cache loaders configured.
Set<?>	getChildrenNames(Fqn fqn) Returns a list of children names, all names are relative.
CacheLoaderConfig.IndividualCacheLoaderConfig	getConfig() Gets the configuration.
int	getSize() Returns the number of cache loaders in the chain.
void	injectDependencies(ComponentRegistry registry)
void	loadEntireState(ObjectOutputStream os) Fetches the entire state for this cache from secondary storage (disk, database) and writes it to a provided ObjectOutputStream.
void	loadState(Fqn subtree, ObjectOutputStream os) Fetches a portion of the state for this cache from secondary storage (disk, database) and writes it to a provided ObjectOutputStream.
void	prepare(Object tx, List modifications, boolean one_phase) Prepare the modifications.
void	purgeIfNecessary()
void	put(Fqn name, Map attributes) Inserts all elements of attributes into the attributes hashmap of the given node, overwriting existing attributes, but not clearing the existing hashmap before insertion (making it a union of existing and new attributes) If the node does not exist, all parent nodes from the root down are created automatically
Object	put(Fqn name, Object key, Object value) Inserts key and value into the attributes hashmap of the given node.
void	put(List<Modification> modifications) Inserts all modifications to the backend store.
void	remove(Fqn name) Removes the given node.
Object	remove(Fqn name, Object key) Removes the given key and value from the attributes of the given node.
void	removeData(Fqn name) Removes all attributes from a given node, but doesn't delete the node itself
void	rollback(Object tx) Roll the transaction back.
void	setConfig(CacheLoaderConfig.IndividualCacheLoaderConfig config) Sets the configuration.
void	setRegionManager(RegionManager manager) No-op, as this class doesn't directly use the ERegionManager.
void	start()
void	stop()
void	storeEntireState(ObjectInputStream is) Stores the entire state for this cache by reading it from a provided ObjectInputStream.
void	storeState(Fqn subtree, ObjectInputStream is) Stores the given portion of the cache tree's state in secondary storage.
String	toString()

Methods inherited from class org.jboss.cache.loader.AbstractCacheLoader

doMarshall, doUnmarshall, getMarshaller, getNodeDataList, loadStateHelper, move, put, regionAwareMarshall, regionAwareUnmarshall, setCache, storeStateHelper

Methods inherited from class java.lang.Object

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

Constructor Detail

ChainingCacheLoader

public ChainingCacheLoader()

Method Detail

setConfig

public void setConfig(CacheLoaderConfig.IndividualCacheLoaderConfig config)

Sets the configuration. Will be called before create() and start()

Parameters:

config - ignored

getConfig

public CacheLoaderConfig.IndividualCacheLoaderConfig getConfig()

Description copied from interface: CacheLoader

Gets the configuration.

Returns:

the configuration, represented by a CacheLoaderConfig.IndividualCacheLoaderConfig object.

injectDependencies

public void injectDependencies(ComponentRegistry registry)

getChildrenNames

public Set<?> getChildrenNames(Fqn fqn)
                        throws Exception

Returns a list of children names, all names are relative. Returns null if the parent node is not found. The returned set must not be modified, e.g. use Collections.unmodifiableSet(s) to return the result

Parameters:

fqn - The FQN of the parent

Returns:

Set. A list of children. Returns null if no children nodes are present, or the parent is not present

Throws:

Exception

get

public Map get(Fqn name)
        throws Exception

Returns all keys and values from the persistent store, given a fully qualified name

Parameters:

name -

Returns:

Map of keys and values for the given node. Returns null if the node was not found, or if the node has no attributes

Throws:

Exception

exists

public boolean exists(Fqn name)
               throws Exception

Checks whether the CacheLoader has a node with Fqn

Parameters:

name -

Returns:

True if node exists, false otherwise

Throws:

Exception

put

public Object put(Fqn name,
         Object key,
         Object value)
           throws Exception

Inserts key and value into the attributes hashmap of the given node. If the node does not exist, all parent nodes from the root down are created automatically. Returns the old value

Throws:

Exception

put

public void put(Fqn name,
       Map attributes)
         throws Exception

Inserts all elements of attributes into the attributes hashmap of the given node, overwriting existing attributes, but not clearing the existing hashmap before insertion (making it a union of existing and new attributes) If the node does not exist, all parent nodes from the root down are created automatically

Parameters:

name - The fully qualified name of the node

attributes - A Map of attributes. Can be null

Throws:

Exception

put

public void put(List<Modification> modifications)
         throws Exception

Inserts all modifications to the backend store. Overwrite whatever is already in the datastore.

Specified by:

put in interface CacheLoader

Overrides:

put in class AbstractCacheLoader

Parameters:

modifications - A List of modifications

Throws:

Exception

remove

public Object remove(Fqn name,
            Object key)
              throws Exception

Removes the given key and value from the attributes of the given node. No-op if node doesn't exist. Returns the first response from the loader chain.

Throws:

Exception

remove

public void remove(Fqn name)
            throws Exception

Removes the given node. If the node is the root of a subtree, this will recursively remove all subnodes, depth-first

Parameters:

name - the Fqn of the node

Throws:

Exception

removeData

public void removeData(Fqn name)
                throws Exception

Removes all attributes from a given node, but doesn't delete the node itself

Parameters:

name -

Throws:

Exception

prepare

public void prepare(Object tx,
           List modifications,
           boolean one_phase)
             throws Exception

Prepare the modifications. For example, for a DB-based CacheLoader:

1. Create a local (JDBC) transaction
2. Associate the local transaction with tx (tx is the key)
3. Execute the coresponding SQL statements against the DB (statements derived from modifications)

For non-transactional CacheLoader (e.g. file-based), this could be a null operation

Specified by:

prepare in interface CacheLoader

Overrides:

prepare in class AbstractCacheLoader

Parameters:

tx - The transaction, just used as a hashmap key

modifications - List, a list of all modifications within the given transaction

one_phase - Persist immediately and (for example) commit the local JDBC transaction as well. When true, we won't get a commit(Object) or rollback(Object) method call later

Throws:

Exception

commit

public void commit(Object tx)
            throws Exception

Commit the transaction. A DB-based CacheLoader would look up the local JDBC transaction asociated with tx and commit that transaction
Non-transactional CacheLoaders could simply write the data that was previously saved transiently under the given tx key, to (for example) a file system (note this only holds if the previous prepare() did not define one_phase=true

Specified by:

commit in interface CacheLoader

Overrides:

commit in class AbstractCacheLoader

Parameters:

tx -

Throws:

Exception

rollback

public void rollback(Object tx)

Roll the transaction back. A DB-based CacheLoader would look up the local JDBC transaction asociated with tx and roll back that transaction

Specified by:

rollback in interface CacheLoader

Overrides:

rollback in class AbstractCacheLoader

Parameters:

tx -

create

public void create()
            throws Exception

Creates individual cache loaders.

Specified by:

create in interface Lifecycle

Overrides:

create in class AbstractCacheLoader

Throws:

Exception

start

public void start()
           throws Exception

Specified by:

start in interface Lifecycle

Overrides:

start in class AbstractCacheLoader

Throws:

Exception

stop

public void stop()

Specified by:

stop in interface Lifecycle

Overrides:

stop in class AbstractCacheLoader

destroy

public void destroy()

Specified by:

destroy in interface Lifecycle

Overrides:

destroy in class AbstractCacheLoader

setRegionManager

public void setRegionManager(RegionManager manager)

No-op, as this class doesn't directly use the ERegionManager.

Specified by:

setRegionManager in interface CacheLoader

Overrides:

setRegionManager in class AbstractCacheLoader

Parameters:

manager - the region manager to use, or null.

loadEntireState

public void loadEntireState(ObjectOutputStream os)
                     throws Exception

Description copied from interface: CacheLoader

Fetches the entire state for this cache from secondary storage (disk, database) and writes it to a provided ObjectOutputStream. State written to the provided ObjectOutputStream parameter is used for initialization of a new CacheImpl instance. When the state gets transferred to the new cache instance its cacheloader calls CacheLoader.storeEntireState(ObjectInputStream)

Implementations of this method should not catch any exception or close the given ObjectOutputStream parameter. In order to ensure cacheloader interoperability contents of the cache are written to the ObjectOutputStream as a sequence of NodeData objects.

Default implementation is provided by AbstractCacheLoader and ensures cacheloader interoperability. Implementors are encouraged to consider extending AbstractCacheLoader prior to implementing completely custom cacheloader.

Specified by:

loadEntireState in interface CacheLoader

Overrides:

loadEntireState in class AbstractCacheLoader

Parameters:

os - ObjectOutputStream to write state

Throws:

Exception

See Also:

AbstractCacheLoader.loadEntireState(ObjectOutputStream), NodeData

loadState

public void loadState(Fqn subtree,
             ObjectOutputStream os)
               throws Exception

Description copied from interface: CacheLoader

Fetches a portion of the state for this cache from secondary storage (disk, database) and writes it to a provided ObjectOutputStream. State written to the provided ObjectOutputStream parameter is used for activation of a portion of a new CacheImpl instance. When the state gets transferred to the new cache instance its cacheloader calls CacheLoader.storeState(Fqn,ObjectInputStream).

Implementations of this method should not catch any exception or close the given ObjectOutputStream parameter. In order to ensure cacheloader interoperability contents of the cache are written to the ObjectOutputStream as a sequence of NodeData objects.

Default implementation is provided by AbstractCacheLoader and ensures cacheloader interoperability. Implementors are encouraged to consider extending AbstractCacheLoader prior to implementing completely custom cacheloader.

Specified by:

loadState in interface CacheLoader

Overrides:

loadState in class AbstractCacheLoader

Parameters:

subtree - Fqn naming the root (i.e. highest level parent) node of the subtree for which state is requested.

os - ObjectOutputStream to write state

Throws:

Exception

See Also:

AbstractCacheLoader.loadState(Fqn,ObjectOutputStream), Region.activate(), NodeData

storeEntireState

public void storeEntireState(ObjectInputStream is)
                      throws Exception

Description copied from interface: CacheLoader

Stores the entire state for this cache by reading it from a provided ObjectInputStream. The state was provided to this cache by calling CacheLoader.loadEntireState(ObjectOutputStream)} on some other cache instance. State currently in storage gets overwritten.

Implementations of this method should not catch any exception or close the given ObjectInputStream parameter. In order to ensure cacheloader interoperability contents of the cache are read from the ObjectInputStream as a sequence of NodeData objects.

Default implementation is provided by AbstractCacheLoader and ensures cacheloader interoperability. Implementors are encouraged to consider extending AbstractCacheLoader prior to implementing completely custom cacheloader.

Specified by:

storeEntireState in interface CacheLoader

Overrides:

storeEntireState in class AbstractCacheLoader

Parameters:

is - ObjectInputStream to read state

Throws:

Exception

See Also:

AbstractCacheLoader.storeEntireState(ObjectInputStream), NodeData

storeState

public void storeState(Fqn subtree,
              ObjectInputStream is)
                throws Exception

Description copied from interface: CacheLoader

Stores the given portion of the cache tree's state in secondary storage. Overwrite whatever is currently in secondary storage. If the transferred state has Fqns equal to or children of parameter subtree, then no special behavior is required. Otherwise, ensure that the state is integrated under the given subtree. Typically in the latter case subtree would be the Fqn of the buddy backup region for a buddy group; e.g.

If the the transferred state had Fqns starting with "/a" and subtree was "/_BUDDY_BACKUP_/192.168.1.2:5555" then the state should be stored in the local persistent store under "/_BUDDY_BACKUP_/192.168.1.2:5555/a"

Implementations of this method should not catch any exception or close the given ObjectInputStream parameter. In order to ensure cacheloader interoperability contents of the cache are read from the ObjectInputStream as a sequence of NodeData objects.

Default implementation is provided by AbstractCacheLoader and ensures cacheloader interoperability. Implementors are encouraged to consider extending AbstractCacheLoader prior to implementing completely custom cacheloader.

Specified by:

storeState in interface CacheLoader

Overrides:

storeState in class AbstractCacheLoader

Parameters:

subtree - Fqn naming the root (i.e. highest level parent) node of the subtree included in state. If the Fqns of the data included in state are not already children of subtree, then their Fqns should be altered to make them children of subtree before they are persisted.

is - ObjectInputStream to read state

Throws:

Exception

See Also:

AbstractCacheLoader.storeState(Fqn,ObjectInputStream), NodeData

getSize

public int getSize()

Returns the number of cache loaders in the chain.

getCacheLoaders

public List<CacheLoader> getCacheLoaders()

Returns a List of individual cache loaders configured.

addCacheLoader

public void addCacheLoader(CacheLoader l,
                  CacheLoaderConfig.IndividualCacheLoaderConfig cfg)

Adds a cache loader to the chain (always added at the end of the chain)

Parameters:

l - the cache loader to add

cfg - and its configuration

toString

public String toString()

Overrides:

toString in class Object

purgeIfNecessary

public void purgeIfNecessary()
                      throws Exception

Throws:

Exception