Package com.helger.commons.id.factory

Class AbstractPersistingLongIDFactory

java.lang.Object
com.helger.commons.id.factory.AbstractPersistingLongIDFactory
All Implemented Interfaces:
IBaseIDFactory, ILongIDFactory
Direct Known Subclasses:
FileLongIDFactory
@ThreadSafe public abstract class AbstractPersistingLongIDFactory extends Object implements ILongIDFactory
This implementation of ILongIDFactory reads IDs from a device. It does it by reserving a range of n IDs so that not each ID reservation requires IO. If only 1 ID is effectively used, the other n-1 IDs are lost and will never be assigned to any object again.
Author:
Philip Helger

  • Field Details

  • Constructor Details

    • AbstractPersistingLongIDFactory

      protected AbstractPersistingLongIDFactory(@Nonnegative int nReserveCount)
      Constructor.
      Parameters:
      nReserveCount - The number of IDs to reserve per persistence layer access. Must be > 0.

  • Method Details

    • getReserveCount

      @Nonnegative public final int getReserveCount()
      Returns:
      The number of IDs to reserve, as provided in the constructor. Always > 0.

    • readAndUpdateIDCounter

      @IsLocked(WRITE) protected abstract long readAndUpdateIDCounter(@Nonnegative int nReserveCount)
      Read the current ID from the device. In case the method is called for a non-initialized device, 0 should be returned.
      The update should write the read value plus the passed reserve count back to the device. This method should perform an atomic read and update to avoid that ID can be reused.
      Pseudo code: 
       protected long readAndUpdateIDCounter (int nReserveCount)
 {
   final long nRead = FileIO.read (file);
   FileIO.write (file, nRead + nReserveCount);
   return nRead;
 }
      Parameters:
      nReserveCount - the number that should be added to the read value. Always > 0.
      Returns:
      0 if this method is called for a non-initialized device, the value read from the device otherwise or CGlobal.ILLEGAL_ULONG in case of an error.

    • getNewID

      public final long getNewID()
      Description copied from interface: ILongIDFactory
      Create a new unique long ID.
      Specified by:
      getNewID in interface ILongIDFactory
      Returns:
      The newly created ID.

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object