org.jboss.cache.loader
Interface CacheLoader

All Superinterfaces:

Service (src)

All Known Subinterfaces:

CacheLoaderAop (src)

All Known Implementing Classes:

BdbjeCacheLoader (src) , DelegatingCacheLoader (src) , FileCacheLoader (src) , JDBCCacheLoader (src) , SharedStoreCacheLoader (src)

public interface CacheLoader

extends Service (src)

Implementations need to load an object given a key from secondary storage, or store an object under a given key in secondary storage (e.g. DB, filesystem).
Lifecycle: first an instance of the loader is created, then the configuration (#setConfig(String)) and cache (setCache(TreeCache)) are set. After this, Service.create() is called. Then @start() is called. When re-deployed, Service.stop() will be called, followed by another Service.start(). Finally, when shut down, Service.destroy() is called, after which the loader is unusable.

setConfig

public void setConfig(java.util.Properties url)

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

Parameters:

url - A list of properties, defined in the XML file

setCache

public void setCache(TreeCache (src)  c)

This method allows the CacheLoader to set the TreeCache, therefore allowing the CacheLoader to invoke methods of the TreeCache. It can also use the TreeCache to fetch configuration information. Alternatively, the CacheLoader could maintain its own configuration
This method will be called directly after the CacheLoader instance has been created

Parameters:

c - The cache on which this loader works

getChildrenNames

public java.util.Set getChildrenNames(Fqn (src)  fqn)
                               throws java.lang.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:

java.lang.Exception

get

public java.lang.Object get(Fqn (src)  name,
                            java.lang.Object key)
                     throws java.lang.Exception

Returns the value for a given key. Returns null if the node doesn't exist, or the value is not bound

Parameters:

name -

Returns:

Throws:

java.lang.Exception

get

public java.util.Map get(Fqn (src)  name)
                  throws java.lang.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:

java.lang.Exception

exists

public boolean exists(Fqn (src)  name)
               throws java.lang.Exception

Checks whether the CacheLoader has a node with Fqn

Parameters:

name -

Returns:

True if node exists, false otherwise

Throws:

java.lang.Exception

put

public java.lang.Object put(Fqn (src)  name,
                            java.lang.Object key,
                            java.lang.Object value)
                     throws java.lang.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:

java.lang.Exception

put

public void put(Fqn (src)  name,
                java.util.Map attributes)
         throws java.lang.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:

java.lang.Exception

put

public void put(java.util.List modifications)
         throws java.lang.Exception

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

Parameters:

modifications - A List of modifications

Throws:

java.lang.Exception

remove

public java.lang.Object remove(Fqn (src)  name,
                               java.lang.Object key)
                        throws java.lang.Exception

Removes the given key and value from the attributes of the given node. No-op if node doesn't exist

Throws:

java.lang.Exception

remove

public void remove(Fqn (src)  name)
            throws java.lang.Exception

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

Throws:

java.lang.Exception

removeData

public void removeData(Fqn (src)  name)
                throws java.lang.Exception

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

Parameters:

name -

Throws:

java.lang.Exception

prepare

public void prepare(java.lang.Object tx,
                    java.util.List modifications,
                    boolean one_phase)
             throws java.lang.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

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:

java.lang.Exception

commit

public void commit(java.lang.Object tx)
            throws java.lang.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

Parameters:

tx -

Throws:

java.lang.Exception

rollback

public void rollback(java.lang.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

Parameters:

tx -

loadEntireState

public byte[] loadEntireState()
                       throws java.lang.Exception

Fetch the entire state for this cache from secondary storage (disk, DB) and return it as a byte buffer. This is for initialization of a new cache from a remote cache. The new cache would then call storeEntireState().
todo: define binary format for exchanging state

Throws:

java.lang.Exception

storeEntireState

public void storeEntireState(byte[] state)
                      throws java.lang.Exception

Store the given state in secondary storage. Overwrite whatever is currently in seconday storage.

Throws:

java.lang.Exception