Module org.eclipse.persistence.core
Package org.eclipse.persistence.internal.indirection

Class QueryBasedValueHolder<T>

java.lang.Object
org.eclipse.persistence.internal.indirection.DatabaseValueHolder<T>
org.eclipse.persistence.internal.indirection.QueryBasedValueHolder<T>
All Implemented Interfaces:
Serializable, Cloneable, ValueHolderInterface<T>, WeavedAttributeValueHolderInterface<T>
Direct Known Subclasses:
BatchValueHolder, EISOneToManyQueryBasedValueHolder
public class QueryBasedValueHolder<T> extends DatabaseValueHolder<T>
QueryBasedValueHolder wraps a database-stored object and implements behavior to access it. The object is read from the database by invoking a user-specified query.
See Also:

  • Field Details

    • query

      protected transient ReadQuery query
      Stores the query to be executed.

    • sourceObject

      protected transient Object sourceObject

    • refreshCascade

      protected Integer refreshCascade

  • Constructor Details

  • Method Details

    • getRefreshCascadePolicy

      public Integer getRefreshCascadePolicy()
      INTERNAL: Returns the refresh cascade policy that was set on the query that was used to instantiate the valueholder a null value means that a non refresh query was used.

    • getValue

      public T getValue(UnitOfWorkImpl uow)
      Process against the UOW and attempt to load a local copy before going to the shared cache If null is returned then the calling UOW will instantiate as normal.
      Overrides:
      getValue in class DatabaseValueHolder<T>

    • getQuery

      public ReadQuery getQuery()
      Return the query. The query for a QueryBasedValueHolder is constructed dynamically based on the original query on the parent object and the mapping configuration. If modifying a query the developer must be careful not to change the results returned as that may cause the application to see incorrect results.

    • instantiate

      protected T instantiate() throws DatabaseException
      Description copied from class: DatabaseValueHolder
      Instantiate the object.
      Specified by:
      instantiate in class DatabaseValueHolder<T>
      Throws:
      DatabaseException

    • instantiate

      protected T instantiate(AbstractSession session) throws DatabaseException
      Instantiate the object by executing the query on the session.
      Throws:
      DatabaseException

    • instantiateForUnitOfWorkValueHolder

      public T instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder<T> 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: This method is not thread-safe. It must be used in a synchronized manner

      Specified by:
      instantiateForUnitOfWorkValueHolder in class DatabaseValueHolder<T>

    • postInstantiate

      public void postInstantiate()
      INTERNAL: Run any extra code required after the valueholder instantiates For query based VH, we notify the cache that the valueholder has been triggered
      Overrides:
      postInstantiate in class DatabaseValueHolder<T>
      See Also:

    • releaseWrappedValueHolder

      public void releaseWrappedValueHolder(AbstractSession targetSession)
      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.

      Overrides:
      releaseWrappedValueHolder in class DatabaseValueHolder<T>

    • resetFields

      protected void resetFields()
      Reset all the fields that are not needed after instantiation.
      Overrides:
      resetFields in class DatabaseValueHolder<T>

    • setQuery

      protected void setQuery(ReadQuery theQuery)
      Set the query.

    • isPessimisticLockingValueHolder

      public boolean isPessimisticLockingValueHolder()
      INTERNAL: 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 instantiated all fields can not be reset.

      Since locks will be issued each time this valueholder is triggered, triggering this directly on the session in auto commit mode will generate an exception. This only UnitOfWorkValueHolder's wrapping this can trigger it. Note: This method is not thread-safe. It must be used in a synchronized manner

      Specified by:
      isPessimisticLockingValueHolder in class DatabaseValueHolder<T>

    • setSourceObject

      public void setSourceObject(Object sourceObject)

    • setRefreshCascadePolicy

      public void setRefreshCascadePolicy(Integer refreshCascadePolicy)
      INTERNAL: