org.apache.torque.oid
Class IDBroker

java.lang.Object
  org.apache.torque.oid.IDBroker

All Implemented Interfaces:

Runnable, IdGenerator

public class IDBroker
extends Object
implements Runnable, IdGenerator

This method of ID generation is used to ensure that code is more database independent. For example, MySQL has an auto-increment feature while Oracle uses sequences. It caches several ids to avoid needing a Connection for every request. This class uses the table ID_TABLE defined in conf/master/id-table-schema.xml. The columns in ID_TABLE are used as follows:
ID_TABLE_ID - The PK for this row (any unique int).
TABLE_NAME - The name of the table you want ids for.
NEXT_ID - The next id returned by IDBroker when it queries the database (not when it returns an id from memory).
QUANTITY - The number of ids that IDBroker will cache in memory.

Use this class like this:

 int id = dbMap.getIDBroker().getNextIdAsInt(null, "TABLE_NAME");
  - or -
 BigDecimal[] ids = ((IDBroker)dbMap.getIDBroker())
     .getNextIds("TABLE_NAME", numOfIdsToReturn);
 

NOTE: When the ID_TABLE must be updated we must ensure that IDBroker objects running in different JVMs do not overwrite each other. This is accomplished using using the transactional support occuring in some databases. Using this class with a database that does not support transactions should be limited to a single JVM.

Version:

$Id: IDBroker.java 1379249 2012-08-31 01:37:19Z tfischer $

Author:

Frank Y. Kim, John D. McNally, Henning P. Schmiedehausen

Field Summary

static String	COL_NEXT_ID Next_ID column name
static String	COL_QUANTITY Quantity column name
static String	COL_TABLE_ID ID column name
static String	COL_TABLE_NAME Table_Name column name
static String	ID_TABLE Name of the ID_TABLE = ID_TABLE
static String	NEXT_ID Fully qualified Next_ID column name
static String	QUANTITY Fully qualified Quantity column name
static String	TABLE_ID Fully qualified ID column name
static String	TABLE_NAME Fully qualified Table_Name column name

Constructor Summary

IDBroker(Database database)
Constructs an IdBroker for the given Database.

Method Summary

boolean	exists(String tableName)
BigDecimal	getIdAsBigDecimal(Connection connection, Object tableName) Returns an id as a BigDecimal.
int	getIdAsInt(Connection connection, Object tableName) Returns an id as a primitive int.
long	getIdAsLong(Connection connection, Object tableName) Returns an id as a primitive long.
String	getIdAsString(Connection connection, Object tableName) Returns an id as a String.
BigDecimal[]	getNextIds(String tableName, int numOfIdsToReturn) This method returns x number of ids for the given table.
BigDecimal[]	getNextIds(String tableName, int numOfIdsToReturn, Connection connection) This method returns x number of ids for the given table.
protected BigDecimal	getQuantity(String tableName) Returns the quantity value for a table.
boolean	isConnectionRequired() A flag to determine whether a Connection is required to generate an id.
boolean	isPostInsert() A flag to determine the timing of the id generation
boolean	isPriorToInsert() A flag to determine the timing of the id generation *
boolean	isThreadRunning() Returns whether the idbroker thread is running.
void	run() A background thread that tries to ensure that when someone asks for ids, that there are already some loaded and that the database is not accessed.
void	setConfiguration(org.apache.commons.configuration.Configuration configuration) Set the configuration
void	start() Starts the idBroker.
void	stop() Shuts down the IDBroker thread.
protected void	updateQuantity(Connection con, String tableName, BigDecimal quantity) Helper method to update a row in the ID_TABLE.

Methods inherited from class java.lang.Object

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

Field Detail

ID_TABLE

public static final String ID_TABLE

Name of the ID_TABLE = ID_TABLE

See Also:

Constant Field Values

COL_TABLE_NAME

public static final String COL_TABLE_NAME

Table_Name column name

See Also:

Constant Field Values

TABLE_NAME

public static final String TABLE_NAME

Fully qualified Table_Name column name

See Also:

Constant Field Values

COL_TABLE_ID

public static final String COL_TABLE_ID

ID column name

See Also:

Constant Field Values

TABLE_ID

public static final String TABLE_ID

Fully qualified ID column name

See Also:

Constant Field Values

COL_NEXT_ID

public static final String COL_NEXT_ID

Next_ID column name

See Also:

Constant Field Values

NEXT_ID

public static final String NEXT_ID

Fully qualified Next_ID column name

See Also:

Constant Field Values

COL_QUANTITY

public static final String COL_QUANTITY

Quantity column name

See Also:

Constant Field Values

QUANTITY

public static final String QUANTITY

Fully qualified Quantity column name

See Also:

Constant Field Values

Constructor Detail

IDBroker

public IDBroker(Database database)

Constructs an IdBroker for the given Database.

Parameters:

database - the database where this IdBroker is running in.

Method Detail

start

public void start()

Starts the idBroker.

setConfiguration

public void setConfiguration(org.apache.commons.configuration.Configuration configuration)

Set the configuration

Parameters:

configuration - the configuration

getIdAsInt

public int getIdAsInt(Connection connection,
                      Object tableName)
               throws TorqueException

Returns an id as a primitive int. Note this method does not require a Connection, it just implements the KeyGenerator interface. if a Connection is needed one will be requested. To force the use of the passed in connection set the configuration property torque.idbroker.usenewconnection = false

Specified by:

getIdAsInt in interface IdGenerator

Parameters:

connection - A Connection.

tableName - an Object that contains additional info.

Returns:

An int with the value for the id.

Throws:

Exception - Database error.

TorqueException - if a Database error occurs.

getIdAsLong

public long getIdAsLong(Connection connection,
                        Object tableName)
                 throws TorqueException

Returns an id as a primitive long. Note this method does not require a Connection, it just implements the KeyGenerator interface. if a Connection is needed one will be requested. To force the use of the passed in connection set the configuration property torque.idbroker.usenewconnection = false

Specified by:

getIdAsLong in interface IdGenerator

Parameters:

connection - A Connection.

tableName - a String that identifies a table.

Returns:

A long with the value for the id.

Throws:

Exception - Database error.

TorqueException - if a Database error occurs.

getIdAsBigDecimal

public BigDecimal getIdAsBigDecimal(Connection connection,
                                    Object tableName)
                             throws TorqueException

Returns an id as a BigDecimal. Note this method does not require a Connection, it just implements the KeyGenerator interface. if a Connection is needed one will be requested. To force the use of the passed in connection set the configuration property torque.idbroker.usenewconnection = false

Specified by:

getIdAsBigDecimal in interface IdGenerator

Parameters:

connection - A Connection.

tableName - a String that identifies a table..

Returns:

A BigDecimal id.

Throws:

Exception - Database error.

TorqueException - if a Database error occurs.

getIdAsString

public String getIdAsString(Connection connection,
                            Object tableName)
                     throws TorqueException

Returns an id as a String. Note this method does not require a Connection, it just implements the KeyGenerator interface. if a Connection is needed one will be requested. To force the use of the passed in connection set the configuration property torque.idbroker.usenewconnection = false

Specified by:

getIdAsString in interface IdGenerator

Parameters:

connection - A Connection should be null.

tableName - a String that identifies a table.

Returns:

A String id

Throws:

Exception - Database error.

TorqueException - if a Database error occurs.

isPriorToInsert

public boolean isPriorToInsert()

A flag to determine the timing of the id generation *

Specified by:

isPriorToInsert in interface IdGenerator

Returns:

a boolean value

isPostInsert

public boolean isPostInsert()

A flag to determine the timing of the id generation

Specified by:

isPostInsert in interface IdGenerator

Returns:

a boolean value

isConnectionRequired

public boolean isConnectionRequired()

A flag to determine whether a Connection is required to generate an id.

Specified by:

isConnectionRequired in interface IdGenerator

Returns:

a boolean value

isThreadRunning

public boolean isThreadRunning()

Returns whether the idbroker thread is running.

Returns:

true if the thread is running, false otherwise.

getNextIds

public BigDecimal[] getNextIds(String tableName,
                               int numOfIdsToReturn)
                        throws Exception

This method returns x number of ids for the given table.

Parameters:

tableName - The name of the table for which we want an id.

numOfIdsToReturn - The desired number of ids.

Returns:

A BigDecimal.

Throws:

Exception - Database error.

getNextIds

public BigDecimal[] getNextIds(String tableName,
                               int numOfIdsToReturn,
                               Connection connection)
                        throws TorqueException

This method returns x number of ids for the given table. Note this method does not require a Connection. If a Connection is needed one will be requested. To force the use of the passed in connection set the configuration property torque.idbroker.usenewconnection = false

Parameters:

tableName - The name of the table for which we want an id.

numOfIdsToReturn - The desired number of ids.

connection - A Connection.

Returns:

A BigDecimal.

Throws:

TorqueException - on a database error.

exists

public boolean exists(String tableName)
               throws Exception

Parameters:

tableName - a String value that is used to identify the row

Returns:

a boolean value

Throws:

TorqueException - if a Torque error occurs.

Exception - if another error occurs.

run

public void run()

A background thread that tries to ensure that when someone asks for ids, that there are already some loaded and that the database is not accessed.

Specified by:

run in interface Runnable

stop

public void stop()

Shuts down the IDBroker thread. Calling this method stops the thread that was started for this instance of the IDBroker.

updateQuantity

protected void updateQuantity(Connection con,
                              String tableName,
                              BigDecimal quantity)
                       throws TorqueException

Helper method to update a row in the ID_TABLE.

Parameters:

con - A Connection.

tableName - The properly escaped name of the table to identify the row.

quantity - An int with the value of the quantity.

Throws:

TorqueException - Database error.

getQuantity

protected BigDecimal getQuantity(String tableName)

Returns the quantity value for a table.

Parameters:

tableName - the name of the table.

Returns:

the quantity value for the table, or null if the table is (still) unknown.