com.amazon.carbonado.sequence
Class SequenceValueGenerator

java.lang.Object
  com.amazon.carbonado.sequence.AbstractSequenceValueProducer
      com.amazon.carbonado.sequence.SequenceValueGenerator

All Implemented Interfaces:

SequenceValueProducer

public class SequenceValueGenerator
extends AbstractSequenceValueProducer

General purpose implementation of a sequence value generator.

Since:

1.2

Author:

Brian S O'Neill, bcastill

See Also:

Sequence, StoredSequence

Field Summary

static int	DEFAULT_INCREMENT
static int	DEFAULT_INITIAL_VALUE
static int	DEFAULT_RESERVE_AMOUNT

Constructor Summary

SequenceValueGenerator(Repository repo, String name)
Construct a new SequenceValueGenerator which might create persistent sequence data if it does not exist.

SequenceValueGenerator(Repository repo, String name, long initialValue, int increment)
Construct a new SequenceValueGenerator which might create persistent sequence data if it does not exist.

SequenceValueGenerator(Repository repo, String name, long initialValue, int increment, int reserveAmount)
Construct a new SequenceValueGenerator which might create persistent sequence data if it does not exist.

Method Summary

int	nextIntValue() Returns the next value from the sequence, which may wrap negative if all positive values are exhausted.
long	nextLongValue() Returns the next value from the sequence, which may wrap negative if all positive values are exhausted.
void	reset(int initialValue) Reset the sequence.
boolean	returnReservedValues() Allow any unused reserved values to be returned for re-use.

Methods inherited from class com.amazon.carbonado.sequence.AbstractSequenceValueProducer

nextDecimalValue, nextNumericalValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_RESERVE_AMOUNT

public static final int DEFAULT_RESERVE_AMOUNT

See Also:

Constant Field Values

DEFAULT_INITIAL_VALUE

public static final int DEFAULT_INITIAL_VALUE

See Also:

Constant Field Values

DEFAULT_INCREMENT

public static final int DEFAULT_INCREMENT

See Also:

Constant Field Values

Constructor Detail

SequenceValueGenerator

public SequenceValueGenerator(Repository repo,
                              String name)
                       throws RepositoryException

Construct a new SequenceValueGenerator which might create persistent sequence data if it does not exist. The initial sequence value is one, and the increment is one.

Parameters:

repo - repository to persist sequence data

name - name of sequence

Throws:

RepositoryException

SequenceValueGenerator

public SequenceValueGenerator(Repository repo,
                              String name,
                              long initialValue,
                              int increment)
                       throws RepositoryException

Construct a new SequenceValueGenerator which might create persistent sequence data if it does not exist.

Parameters:

repo - repository to persist sequence data

name - name of sequence

initialValue - initial sequence value, if sequence needs to be created

increment - amount to increment sequence by

Throws:

RepositoryException

SequenceValueGenerator

public SequenceValueGenerator(Repository repo,
                              String name,
                              long initialValue,
                              int increment,
                              int reserveAmount)
                       throws RepositoryException

Construct a new SequenceValueGenerator which might create persistent sequence data if it does not exist.

Parameters:

repo - repository to persist sequence data

name - name of sequence

initialValue - initial sequence value, if sequence needs to be created

increment - amount to increment sequence by

reserveAmount - amount of sequence values to reserve

Throws:

RepositoryException

Method Detail

reset

public void reset(int initialValue)
           throws FetchException,
                  PersistException

Reset the sequence.

Parameters:

initialValue - first value produced by sequence

Throws:

FetchException

PersistException

nextLongValue

public long nextLongValue()
                   throws PersistException

Returns the next value from the sequence, which may wrap negative if all positive values are exhausted. When sequence wraps back to initial value, the sequence is fully exhausted, and an exception is thrown to indicate this.

Note: this method throws PersistException even for fetch failures since this method is called by insert operations. Insert operations can only throw a PersistException.

Throws:

PersistException - for fetch/persist failure or if sequence is exhausted.

nextIntValue

public int nextIntValue()
                 throws PersistException

Returns the next value from the sequence, which may wrap negative if all positive values are exhausted. When sequence wraps back to initial value, the sequence is fully exhausted, and an exception is thrown to indicate this.

Note: this method throws PersistException even for fetch failures since this method is called by insert operations. Insert operations can only throw a PersistException.

Specified by:

nextIntValue in interface SequenceValueProducer

Overrides:

nextIntValue in class AbstractSequenceValueProducer

Throws:

PersistException - for fetch/persist failure or if sequence is exhausted for int values.

returnReservedValues

public boolean returnReservedValues()
                             throws FetchException,
                                    PersistException

Allow any unused reserved values to be returned for re-use. If the repository is shared by other processes, then reserved values might not be returnable.

This method should be called during the shutdown process of a repository, although calling it does not invalidate this SequenceValueGenerator. If getNextValue is called again, it will reserve values again.

Returns:

true if reserved values were returned

Throws:

FetchException

PersistException