org.apache.derby.impl.store.access
Class CacheableConglomerate

java.lang.Object
  extended byorg.apache.derby.impl.store.access.CacheableConglomerate
All Implemented Interfaces:
Cacheable

class CacheableConglomerate
extends java.lang.Object
implements Cacheable

The CacheableConglomerate implements a single item in the cache used by the Conglomerate directory to cache Conglomerates. It is simply a wrapper object for the conglomid and Conglomerate object that is read from the Conglomerate Conglomerate. It is a wrapper rather than extending the conglomerate implementations because we want to cache all conglomerate implementatations: (ie. Heap, B2I, ...). References to the Conglomerate objects cached by this wrapper will be handed out to callers. When this this object goes out of cache callers may still have references to the Conglomerate objects, which we are counting on java to garbage collect. The Conglomerate Objects never change after they are created.


Field Summary
private  Conglomerate conglom
           
private  java.lang.Long conglomid
           
 
Constructor Summary
(package private) CacheableConglomerate()
           
 
Method Summary
 void clean(boolean forRemove)
          Clean the object.
 void clearIdentity()
          Put the object into the No Identity state.
 Cacheable createIdentity(java.lang.Object key, java.lang.Object createParameter)
          Create a new item and set the identity of the object to represent it.
protected  Conglomerate getConglom()
           
 java.lang.Object getIdentity()
          Get the identity of this object.
 boolean isDirty()
          Returns true of the object is dirty.
 Cacheable setIdentity(java.lang.Object key)
          Set the identity of the object to represent an item that already exists, e.g. an existing container.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

conglomid

private java.lang.Long conglomid

conglom

private Conglomerate conglom
Constructor Detail

CacheableConglomerate

CacheableConglomerate()
Method Detail

getConglom

protected Conglomerate getConglom()

setIdentity

public Cacheable setIdentity(java.lang.Object key)
                      throws StandardException
Set the identity of the object to represent an item that already exists, e.g. an existing container. The object will be in the No Identity state, ie. it will have just been created or clearIdentity() was just called.
The object must copy the information out of key, not just store a reference to key. After this call the expression getIdentity().equals(key) must return true.
If the class of the object needs to change (e.g. to support a different format) then the object should create a new object, call its initParameter() with the parameters the original object was called with, set its identity and return a reference to it. The cache manager will discard the reference to the old object.
If an exception is thrown the object must be left in the no-identity state.
MT - single thread required - Method must only be called be cache manager and the cache manager will guarantee only one thread can be calling it.

Specified by:
setIdentity in interface Cacheable
Returns:
an object reference if the object can take on the identity, null otherwise.
Throws:
StandardException - Standard Cloudscape Policy
See Also:
CacheManager.find(java.lang.Object)

createIdentity

public Cacheable createIdentity(java.lang.Object key,
                                java.lang.Object createParameter)
                         throws StandardException
Create a new item and set the identity of the object to represent it. The object will be in the No Identity state, ie. it will have just been created or clearIdentity() was just called.
The object must copy the information out of key, not just store a reference to key. After this call the expression getIdentity().equals(key) must return true.
If the class of the object needs to change (e.g. to support a different format) then the object should create a new object, call its initParameter() with the parameters the original object was called with, set its identity and return a reference to it. The cache manager will discard the reference to the old object.
If an exception is thrown the object must be left in the no-identity state.
MT - single thread required - Method must only be called be cache manager and the cache manager will guarantee only one thread can be calling it.

Specified by:
createIdentity in interface Cacheable
Returns:
an object reference if the object can take on the identity, null otherwise.
Throws:
StandardException - If forCreate is true and the object cannot be created.
See Also:
CacheManager.create(java.lang.Object, java.lang.Object)

clearIdentity

public void clearIdentity()
Put the object into the No Identity state.
MT - single thread required - Method must only be called be cache manager and the cache manager will guarantee only one thread can be calling it.

Specified by:
clearIdentity in interface Cacheable

getIdentity

public java.lang.Object getIdentity()
Get the identity of this object.
MT - thread safe.

Specified by:
getIdentity in interface Cacheable

isDirty

public boolean isDirty()
Returns true of the object is dirty. Will only be called when the object is unkept.
MT - thread safe

Specified by:
isDirty in interface Cacheable

clean

public void clean(boolean forRemove)
           throws StandardException
Clean the object. It is up to the object to ensure synchronization of the isDirty() and clean() method calls.
If forRemove is true then the object is being removed due to an explict remove request, in this case the cache manager will have called this method regardless of the state of the isDirty()
If an exception is thrown the object must be left in the clean state.
MT - thread safe - Can be called at any time by the cache manager, it is the responsibility of the object implementing Cacheable to ensure any users of the object do not conflict with the clean call.

Specified by:
clean in interface Cacheable
Throws:
StandardException - Standard Cloudscape error policy.


Apache Derby V10.0 Engine Documentation - Copyright © 1997,2004 The Apache Software Foundation or its licensors, as applicable.