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:

IdGenerator, org.apache.avalon.framework.activity.Disposable, org.apache.avalon.framework.activity.Initializable, org.apache.avalon.framework.component.Component, org.apache.avalon.framework.configuration.Configurable, org.apache.avalon.framework.logger.LogEnabled, org.apache.avalon.framework.service.Serviceable, org.apache.avalon.framework.thread.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

Modifier and Type	Field and Description
private java.lang.String	m_query

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

Constructors

Constructor and Description
SequenceIdGenerator()

Method Summary

Methods

Modifier and Type	Method and Description
void	configure(org.apache.avalon.framework.configuration.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

Field Detail

m_query

private java.lang.String m_query

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(org.apache.avalon.framework.configuration.Configuration configuration)
               throws org.apache.avalon.framework.configuration.ConfigurationException

Called by the Container to configure the component.

Specified by:

configure in interface org.apache.avalon.framework.configuration.Configurable

Overrides:

configure in class AbstractDataSourceIdGenerator

Parameters:

configuration - configuration info used to setup the component.

Throws:

org.apache.avalon.framework.configuration.ConfigurationException - if there are any problems with the configuration.