| org.apache.derby.iapi.services.cache.Cacheable
All known Subclasses: org.apache.derby.impl.store.raw.data.FileContainer, org.apache.derby.impl.store.raw.data.CachedPage, org.apache.derby.impl.sql.catalog.SPSNameCacheable, org.apache.derby.impl.sql.catalog.TDCacheable, org.apache.derby.impl.store.access.CacheableConglomerate, org.apache.derby.impl.services.bytecode.VMTypeIdCacheable, org.apache.derby.impl.sql.conn.CachedStatement, org.apache.derby.impl.sql.catalog.PermissionsCacheable, org.apache.derbyTesting.unitTests.services.T_Cacheable,
| Cacheable | | public interface Cacheable (Code) | | Any object that implements this interface can be cached using the services of
the CacheManager/CacheFactory. In addition to implementing this interface the
class must be public and it must have a public no-arg constructor. This is because
the cache manager will construct objects itself and then set their identity
by calling the setIdentity method.
A Cacheable object has five states:
- No identity - The object is only accessable by the cache manager
- Identity, clean, unkept - The object has an identity, is clean but is only accessable by the cache manager
- Identity, clean, kept - The object has an identity, is clean, and is in use by one or more threads
- Identity, kept, dirty - The object has an identity, is dirty, and is in use by one or more threads
- Identity, unkept, dirty - The object has an identity, is dirty but is only accessable by the cache manager
While the object is kept it is guaranteed
not to change identity. While it is unkept no-one outside of the
cache manager can have a reference to the object.
The cache manager returns kept objects and they return to the unkept state
when all the current users of the object have released it.
It is required that the object can only move into a dirty state while it is kept.
MT - Mutable : thread aware - Calls to Cacheable method must only be made by the
cache manager or the object itself.
See Also: CacheManager
See Also: CacheFactory
See Also: Class.newInstance |
| Method Summary | |
| public void | clean(boolean forRemove)
Clean the object. | | public void | clearIdentity()
Put the object into the No Identity state. | | public Cacheable | createIdentity(Object key, Object createParameter)
Create a new item.
Create a new item and set the identity of the object to represent it.
The object will be in the No Identity state,
ie. | | public Object | getIdentity()
Get the identity of this object. | | public boolean | isDirty()
Returns true of the object is dirty. | | public Cacheable | setIdentity(Object key)
Set the identity of the object.
Set the identity of the object to represent an item that already exists,
e.g. |
| clean | | public void clean(boolean forRemove) throws StandardException(Code) | | 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.
exception:
StandardException - Standard Cloudscape error policy. |
| clearIdentity | | public void clearIdentity()(Code) | | 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.
|
| createIdentity | | public Cacheable createIdentity(Object key, Object createParameter) throws StandardException(Code) | | Create a new item.
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
if the key is not immutable.
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.
an object reference if the object can take on the identity, null otherwise.
exception:
StandardException - If forCreate is true and the object cannot be created.
See Also: CacheManager.create |
| getIdentity | | public Object getIdentity()(Code) | | Get the identity of this object.
MT - thread safe.
|
| isDirty | | public boolean isDirty()(Code) | | Returns true of the object is dirty.
May be called when the object is kept or unkept.
MT - thread safe
|
| setIdentity | | public Cacheable setIdentity(Object key) throws StandardException(Code) | | Set the identity of the object.
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.
an object reference if the object can take on the identity, null otherwise.
exception:
StandardException - Standard Cloudscape Policy
See Also: CacheManager.find |
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