org.apache.ojb.broker.util.sequence
Class SequenceManagerStoredProcedureImpl

java.lang.Object
  org.apache.ojb.broker.util.sequence.AbstractSequenceManager
      org.apache.ojb.broker.util.sequence.SequenceManagerStoredProcedureImpl

All Implemented Interfaces:

SequenceManager

public class SequenceManagerStoredProcedureImpl
extends AbstractSequenceManager

This solution will give those seeking an oracle-style sequence generator a final answer (Identity columns really suck).
The SequenceManagerStoredProcedureImpl implementation enabled database sequence key generation for all databases (e.g. MSSQL, MySQL, DB2, ...) with a JDBC 2.0 compliant driver.
First add a new table OJB_NEXTVAL_SEQ to your database.

 CREATE TABLE OJB_NEXTVAL_SEQ
 (
     SEQ_NAME    VARCHAR(150) NOT NULL,
     MAX_KEY     BIGINT,
     CONSTRAINT SYS_PK_OJB_NEXTVAL_SEQ PRIMARY KEY(SEQ_NAME)
 )
 

You will also need the stored procedure OJB_NEXTVAL will will take care of giving you a guaranteed unique sequence number, in multi server environments.

 CREATE PROCEDURE ojb_nextval_proc @SEQ_NAME varchar(100)
              AS
                declare @MAX_KEY BIGINT
              -- return an error if sequence does not exist
              -- so we will know if someone truncates the table
              set @MAX_KEY = 0

              UPDATE OJB_NEXTVAL_SEQ
              SET    @MAX_KEY = MAX_KEY = MAX_KEY + 1
              WHERE  SEQ_NAME = @SEQ_NAME

                if @MAX_KEY = 0
                        select 1/0
                else
                        select @MAX_KEY

              RETURN @MAX_KEY
 

It is possible to define a sequence-name field-descriptor attribute in the repository file. If such an attribute was not found, the implementation build an extent aware sequence name by its own.
Keep in mind when define a sequence name, that you are responsible to be aware of extents, that is: if you ask for an uid for an interface with several implementor classes, or a baseclass with several subclasses the returned uid have to be unique accross all tables representing objects of the extent in question. Thus you have to use the same sequence-name for all extents.

Implementation configuration properties:

Property Key	Property Values
autoNaming	Default was 'true'. If set 'true' OJB try to build a sequence name automatic if none found in field-descriptor and set this generated name as sequence-name in field-descriptor. If set 'false' OJB throws an exception if none sequence name was found in field-descriptor.

Limitations:

• do not use when other application use the native key generation ditto

Version:

$Id: SequenceManagerStoredProcedureImpl.java,v 1.1 2007-08-24 22:17:29 ewestfal Exp $

Author:

Ryan Vanderwerf, Edson Carlos Ericksson Richter, Rajeev Kaul, Thomas Mahler, Armin Waibel

Field Summary

protected static String	PROCEDURE_NAME
protected static String	SEQ_ID_STRING
protected static String	SEQ_NAME_STRING
protected static String	SEQ_TABLE_NAME

Fields inherited from class org.apache.ojb.broker.util.sequence.AbstractSequenceManager

GLOBAL_SEQUENCE_NAME, PROPERTY_AUTO_NAMING

Constructor Summary

SequenceManagerStoredProcedureImpl(PersistenceBroker broker)
Constructor

Method Summary

protected long	buildNextSequence(PersistenceBroker broker, ClassDescriptor cld, String sequenceName) Calls the stored procedure stored procedure throws an error if it doesn't exist.
protected void	createSequence(PersistenceBroker broker, FieldDescriptor field, String sequenceName, long maxKey) Creates new row in table
protected long	getUniqueLong(FieldDescriptor field) Gets the actual key - will create a new row with the max key of table if it does not exist.
protected String	sp_createSequenceQuery(String sequenceName, long maxKey) Insert syntax for our special table

Methods inherited from class org.apache.ojb.broker.util.sequence.AbstractSequenceManager

afterStore, calculateSequenceName, getBrokerForClass, getConfigurationProperties, getConfigurationProperty, getPlatform, getUniqueValue, setConfigurationProperties, setConfigurationProperty, setReferenceFKs, useAutoNaming

Methods inherited from class java.lang.Object

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

Field Detail

PROCEDURE_NAME

protected static final String PROCEDURE_NAME

See Also:

Constant Field Values

SEQ_NAME_STRING

protected static final String SEQ_NAME_STRING

See Also:

Constant Field Values

SEQ_ID_STRING

protected static final String SEQ_ID_STRING

See Also:

Constant Field Values

SEQ_TABLE_NAME

protected static final String SEQ_TABLE_NAME

See Also:

Constant Field Values

Constructor Detail

SequenceManagerStoredProcedureImpl

public SequenceManagerStoredProcedureImpl(PersistenceBroker broker)

Constructor

Parameters:

broker -

Method Detail

sp_createSequenceQuery

protected String sp_createSequenceQuery(String sequenceName,
                                        long maxKey)

Insert syntax for our special table

Parameters:

sequenceName -

maxKey -

Returns:

sequence insert statement

getUniqueLong

protected long getUniqueLong(FieldDescriptor field)
                      throws SequenceManagerException

Gets the actual key - will create a new row with the max key of table if it does not exist.

Specified by:

getUniqueLong in class AbstractSequenceManager

Parameters:

field -

Returns:

Throws:

SequenceManagerException

buildNextSequence

protected long buildNextSequence(PersistenceBroker broker,
                                 ClassDescriptor cld,
                                 String sequenceName)
                          throws LookupException,
                                 SQLException,
                                 PlatformException

Calls the stored procedure stored procedure throws an error if it doesn't exist.

Parameters:

broker -

cld -

sequenceName -

Returns:

Throws:

LookupException

SQLException

PlatformException

createSequence

protected void createSequence(PersistenceBroker broker,
                              FieldDescriptor field,
                              String sequenceName,
                              long maxKey)
                       throws Exception

Creates new row in table

Parameters:

broker -

field -

sequenceName -

maxKey -

Throws:

Exception