org.apache.avalon.excalibur.datasource.ids
Class SequenceIdGenerator

java.lang.Object
  org.apache.avalon.framework.logger.AbstractLogEnabled
      org.apache.avalon.excalibur.datasource.ids.AbstractIdGenerator
          org.apache.avalon.excalibur.datasource.ids.AbstractDataSourceIdGenerator
              org.apache.avalon.excalibur.datasource.ids.SequenceIdGenerator

All Implemented Interfaces:

Component, Configurable, Disposable, IdGenerator, Initializable, LogEnabled, Serviceable, ThreadSafe

public class SequenceIdGenerator

extends AbstractDataSourceIdGenerator

The SequenceIdGenerator requests each Id using a sequence in a database. While not actually pooling batches of Ids like other IdGenerator implementations, making use of this class does make code compatable with other IdGenerators on a configuration basis.

The Configuration to use a SequenceIdGenerator look like the following:

   <id-generators>
       <sequence name="user-ids" logger="cm.ids">
           <dbpool>user-db</dbpool>
           <query>SELECT NEXTVAL('category_ids')</query>
       </sequence>
   </id-generators>
 

or

   <id-generators>
       <sequence name="user-ids" logger="cm.ids">
           <dbpool>user-db</dbpool>
           <query>SELECT category_ids.nextval FROM DUAL</query>
       </sequence>
   </id-generators>
 

Where user-db is the name of a DataSource configured in a datasources element, and query is any query which will return a single id while maintaining state so that successive calls will continue to return incremented ids.

With the following roles declaration:

   <role name="org.apache.avalon.excalibur.datasource.ids.IdGeneratorSelector"
         shorthand="id-generators"
         default-class="org.apache.avalon.excalibur.component.ExcaliburComponentSelector">
       <hint shorthand="sequence"
             class="org.apache.avalon.excalibur.datasource.ids.SequenceIdGenerator"/>
   </role>
 

To configure your component to use the IdGenerator declared above, its configuration should look something like the following:

   <user-service logger="cm">
       <dbpool>user-db</dbpool>
       <id-generator>user-ids</id-generator>
   </user-service>
 

Your component obtains a reference to an IdGenerator using the same method as it obtains a DataSource, by making use of a ComponentSelector.

Since:

4.1

Version:

CVS $Revision: 1.4 $ $Date: 2004/02/28 11:47:17 $

Author:

Avalon Development Team

Field Summary

Fields inherited from class org.apache.avalon.excalibur.datasource.ids.AbstractDataSourceIdGenerator

m_allocated, m_dataSource, m_nextId

Fields inherited from interface org.apache.avalon.excalibur.datasource.ids.IdGenerator

ROLE

Constructor Summary

SequenceIdGenerator()

Method Summary

void	configure(Configuration configuration) Called by the Container to configure the component.
protected java.math.BigDecimal	getNextBigDecimalIdInner() Gets the next id as a Big Decimal.
protected long	getNextLongIdInner() Gets the next id as a long.

Methods inherited from class org.apache.avalon.excalibur.datasource.ids.AbstractDataSourceIdGenerator

dispose, getConnection, initialize, service

Methods inherited from class org.apache.avalon.excalibur.datasource.ids.AbstractIdGenerator

getNextBigDecimalId, getNextByteId, getNextIntegerId, getNextLongId, getNextLongIdChecked, getNextShortId, isUsingBigDecimals, setUseBigDecimals

Methods inherited from class org.apache.avalon.framework.logger.AbstractLogEnabled

enableLogging, getLogger, setupLogger, setupLogger, setupLogger

Methods inherited from class java.lang.Object

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

Constructor Detail

SequenceIdGenerator

public SequenceIdGenerator()

Method Detail

getNextBigDecimalIdInner

protected java.math.BigDecimal getNextBigDecimalIdInner()
                                                 throws IdException

Gets the next id as a Big Decimal. This method will only be called when synchronized and when the data type is configured to be BigDecimal.

Specified by:

getNextBigDecimalIdInner in class AbstractIdGenerator

Returns:

the next id as a BigDecimal.

Throws:

IdException - if an Id could not be allocated for any reason.

getNextLongIdInner

protected long getNextLongIdInner()
                           throws IdException

Gets the next id as a long. This method will only be called when synchronized and when the data type is configured to be long.

Specified by:

getNextLongIdInner in class AbstractIdGenerator

Returns:

the next id as a long.

Throws:

IdException - if an Id could not be allocated for any reason.

configure

public void configure(Configuration configuration)
               throws ConfigurationException

Called by the Container to configure the component.

Specified by:

configure in interface Configurable

Overrides:

configure in class AbstractDataSourceIdGenerator

Parameters:

configuration - configuration info used to setup the component.

Throws:

ConfigurationException - if there are any problems with the configuration.