DatabaseValueHolder (toplink-essentials 2.0.46 API)

java.lang.Object
- oracle.toplink.essentials.internal.indirection.DatabaseValueHolder

All Implemented Interfaces:

Serializable, Cloneable, ValueHolderInterface, WeavedAttributeValueHolderInterface

Direct Known Subclasses:

QueryBasedValueHolder, UnitOfWorkValueHolder
```
public abstract class DatabaseValueHolder
extends Object
implements WeavedAttributeValueHolderInterface, Cloneable, Serializable
```
DatabaseValueHolder wraps a database-stored object and implements behavior to access it. The object is read only once from database after which is cached for faster access.

Author:

Dorin Sandu

See Also:

ValueHolderInterface, Serialized Form

Field Summary

Fields
Modifier and Type	Field and Description
`protected boolean`	`isCoordinatedWithProperty` The variable below is used as part of the implementation of WeavedAttributeValueHolderInterface It is used to track whether a valueholder that has been weaved into a class is coordinated with the underlying property Set internally in TopLink when the state of coordination between a weaved valueholder and the underlying property is known
`protected boolean`	`isInstantiated` Indicates whether the object has been read from the database or not.
`protected AbstractRecord`	`row` Stores the row representation of the object.
`protected AbstractSession`	`session` Stores the session for the database that contains the object.
`protected Object`	`value` Stores the object after it is read from the database.

Fields inherited from interface oracle.toplink.essentials.indirection.ValueHolderInterface
shouldToStringInstantiate

Constructor Summary

Constructors
Constructor and Description

DatabaseValueHolder()

Constructors
Constructor and Description
`DatabaseValueHolder()`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`Object`	`clone()`
`AbstractRecord`	`getRow()` Return the row.
`AbstractSession`	`getSession()` Return the session.
`Object`	`getValue()` Return the object.
`protected abstract Object`	`instantiate()` Instantiate the object.
`abstract Object`	`instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder unitOfWorkValueHolder)` Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).
`boolean`	`isCoordinatedWithProperty()` This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used to check whether a valueholder that has been weaved into a class is coordinated with the underlying property
`boolean`	`isEasilyInstantiated()` INTERNAL: Answers if this valueholder is easy to instantiate.
`boolean`	`isInstantiated()` Return a boolean indicating whether the object has been read from the database or not.
`boolean`	`isNewlyWeavedValueHolder()` This method is used as part of the implementation of WeavedAttributeValueHolderInterface.
`abstract boolean`	`isPessimisticLockingValueHolder()` Answers if this valueholder is a pessimistic locking one.
`boolean`	`isSerializedRemoteUnitOfWorkValueHolder()` Used to determine if this is a remote uow value holder that was serialized to the server.
`protected boolean`	`isTransactionalValueHolder()` Answers if this valueholder is referenced only by a UnitOfWork valueholder.
`void`	`privilegedSetValue(Object value)` Set the object.
`void`	`releaseWrappedValueHolder()` Releases a wrapped valueholder privately owned by a particular unit of work.
`protected void`	`resetFields()` Reset all the fields that are not needed after instantiation.
`void`	`setInstantiated()` Set the instantiated flag to true.
`void`	`setIsCoordinatedWithProperty(boolean coordinated)` This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used internally by TopLink to set whether a valueholder that has been weaved into a class is coordinated with the underlying property
`void`	`setIsNewlyWeavedValueHolder(boolean isNew)` This method is used as part of the implementation of WeavedAttributeValueHolderInterface A DatabaseValueHolder is set up by TopLink and will never be a newly weaved valueholder As a result, this method is stubbed out.
`void`	`setRow(AbstractRecord row)` Set the row.
`void`	`setSession(AbstractSession session)` Set the session.
`void`	`setUninstantiated()` Set the instantiated flag to false.
`void`	`setValue(Object value)` Set the object.
`String`	`toString()`

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - value
```
protected Object value
```
    Stores the object after it is read from the database.
  - isInstantiated
```
protected boolean isInstantiated
```
    Indicates whether the object has been read from the database or not.
  - session
```
protected transient AbstractSession session
```
    Stores the session for the database that contains the object.
  - row
```
protected AbstractRecord row
```
    Stores the row representation of the object.
  - isCoordinatedWithProperty
```
protected boolean isCoordinatedWithProperty
```
    The variable below is used as part of the implementation of WeavedAttributeValueHolderInterface It is used to track whether a valueholder that has been weaved into a class is coordinated with the underlying property Set internally in TopLink when the state of coordination between a weaved valueholder and the underlying property is known
- Constructor Detail
  - DatabaseValueHolder
```
public DatabaseValueHolder()
```
- Method Detail
  - clone
```
public Object clone()
```
    Overrides:
    
    clone in class Object
  - getRow
```
public AbstractRecord getRow()
```
    Return the row.
  - getSession
```
public AbstractSession getSession()
```
    Return the session.
  - getValue
```
public Object getValue()
```
    Return the object.
    
    Specified by:
    
    getValue in interface ValueHolderInterface
  - instantiate
```
protected abstract Object instantiate()
                               throws DatabaseException
```
    Instantiate the object.
    
    Throws:
    
    DatabaseException
  - instantiateForUnitOfWorkValueHolder
```
public abstract Object instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder unitOfWorkValueHolder)
```
    Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).
    When in transaction and/or for pessimistic locking the UnitOfWorkValueHolder needs to be triggered directly without triggering the wrapped valueholder. However only the wrapped valueholder knows how to trigger the indirection, i.e. it may be a batchValueHolder, and it stores all the info like the row and the query. Note: Implementations of this method are not necessarily thread-safe. They must be used in a synchronizaed manner
  - isCoordinatedWithProperty
```
public boolean isCoordinatedWithProperty()
```
    This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used to check whether a valueholder that has been weaved into a class is coordinated with the underlying property
    
    Specified by:
    
    isCoordinatedWithProperty in interface WeavedAttributeValueHolderInterface
    
    Returns:
  - isNewlyWeavedValueHolder
```
public boolean isNewlyWeavedValueHolder()
```
    This method is used as part of the implementation of WeavedAttributeValueHolderInterface. A DatabaseValueHolder is set up by TopLink and will never be a newly weaved valueholder. As a result, this method is stubbed out.
    
    Specified by:
    
    isNewlyWeavedValueHolder in interface WeavedAttributeValueHolderInterface
    
    Returns:
  - isEasilyInstantiated
```
public boolean isEasilyInstantiated()
```
    INTERNAL: Answers if this valueholder is easy to instantiate.
    
    Returns:
    
    true if getValue() won't trigger a database read.
  - isInstantiated
```
public boolean isInstantiated()
```
    Return a boolean indicating whether the object has been read from the database or not.
    
    Specified by:
    
    isInstantiated in interface ValueHolderInterface
  - isPessimisticLockingValueHolder
```
public abstract boolean isPessimisticLockingValueHolder()
```
    Answers if this valueholder is a pessimistic locking one. Such valueholders are special in that they can be triggered multiple times by different UnitsOfWork. Each time a lock query will be issued. Hence even if instantiated it may have to be instantiated again, and once instantatiated all fields can not be reset. Note: Implementations of this method are not necessarily thread-safe. They must be used in a synchronizaed manner
  - isTransactionalValueHolder
```
protected boolean isTransactionalValueHolder()
```
    Answers if this valueholder is referenced only by a UnitOfWork valueholder. I.e. it was built in valueFromRow which was called by buildCloneFromRow.
    Sometimes in transaction a UnitOfWork clone, and all valueholders, are built directly from the row; however a UnitOfWorkValueHolder does not know how to instantiate itself so wraps this which does.
    On a successful merge must be released to the session cache with releaseWrappedValueHolder.
  - isSerializedRemoteUnitOfWorkValueHolder
```
public boolean isSerializedRemoteUnitOfWorkValueHolder()
```
    Used to determine if this is a remote uow value holder that was serialized to the server. It has no reference to its wrapper value holder, so must find its original object to be able to instantiate.
  - privilegedSetValue
```
public void privilegedSetValue(Object value)
```
    Set the object. This is used only by the privileged methods. One must be very careful in using this method.
  - releaseWrappedValueHolder
```
public void releaseWrappedValueHolder()
```
    Releases a wrapped valueholder privately owned by a particular unit of work.
    When unit of work clones are built directly from rows no object in the shared cache points to this valueholder, so it can store the unit of work as its session. However once that UnitOfWork commits and the valueholder is merged into the shared cache, the session needs to be reset to the root session, ie. the server session.
  - resetFields
```
protected void resetFields()
```
    Reset all the fields that are not needed after instantiation.
  - setIsCoordinatedWithProperty
```
public void setIsCoordinatedWithProperty(boolean coordinated)
```
    This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used internally by TopLink to set whether a valueholder that has been weaved into a class is coordinated with the underlying property
    
    Specified by:
    
    setIsCoordinatedWithProperty in interface WeavedAttributeValueHolderInterface
  - setIsNewlyWeavedValueHolder
```
public void setIsNewlyWeavedValueHolder(boolean isNew)
```
    This method is used as part of the implementation of WeavedAttributeValueHolderInterface A DatabaseValueHolder is set up by TopLink and will never be a newly weaved valueholder As a result, this method is stubbed out.
    
    Specified by:
    
    setIsNewlyWeavedValueHolder in interface WeavedAttributeValueHolderInterface
  - setInstantiated
```
public void setInstantiated()
```
    Set the instantiated flag to true.
  - setRow
```
public void setRow(AbstractRecord row)
```
    Set the row.
  - setSession
```
public void setSession(AbstractSession session)
```
    Set the session.
  - setUninstantiated
```
public void setUninstantiated()
```
    Set the instantiated flag to false.
  - setValue
```
public void setValue(Object value)
```
    Set the object.
    
    Specified by:
    
    setValue in interface ValueHolderInterface
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class DatabaseValueHolder

Field Summary

Fields inherited from interface oracle.toplink.essentials.indirection.ValueHolderInterface

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

value

isInstantiated

session

row

isCoordinatedWithProperty

Constructor Detail

DatabaseValueHolder

Method Detail

clone

getRow

getSession

getValue

instantiate

instantiateForUnitOfWorkValueHolder

isCoordinatedWithProperty

isNewlyWeavedValueHolder

isEasilyInstantiated

isInstantiated

isPessimisticLockingValueHolder

isTransactionalValueHolder

isSerializedRemoteUnitOfWorkValueHolder

privilegedSetValue

releaseWrappedValueHolder

resetFields

setIsCoordinatedWithProperty

setIsNewlyWeavedValueHolder

setInstantiated

setRow

setSession

setUninstantiated

setValue

toString