Any plans for built-in optimistic locking for future version

[mboulatian]

I posted several times about built-in optimistic locking for jboss. I've received no responses from any of the developers or jboss people themselves. After my own tests, and considering the fact that no one responded my postings from jboss as well, I came to conclusion that there is no built-in optimistic locking for jboss. I don't know how someone can use ejb 2.0 with jboss if xdoclet suggested soft locking mechanism does not seem to work because ejbStore is called many times during the transaction even when there is no update to the bean's state. I would like to find out though if there are any plans for implementing built-in optimistic locking for jboss in future versions.

[darryl_staflund]

Hi there,

Optimistic Locking is built into JBoss 3.2 as far as I can tell. I've used it a bit and it works fairly well although it still seems buggy to me in some places. For example, if I have two entity beans A and B such that Entity Bean A contains an aggregation of Entity Bean B's and Entity Bean B references an Entity Bean A (but in such a way that no circles are formed, i.e. the Entity Bean A referenced by Entity Bean B does not itself contain Entity Bean B in its aggregation of Entity Bean B's) then the counts involved in the locking get out of synch.

So optimistic locking is there but it's a bit buggy -- or at least I think it is in some cases because I can find no docs to check my problem against :-)

Darryl

PS: I will attach a code sample in a subsequent post to show you how I implemented it.

[darryl_staflund]

Hi again,

Okay, attached is a zip file that demonstrates how I implemented optimistic locking in my code. There are four files:

security.sql
========
This is the PostgreSQL database schema of a table named 'group'. It defines a field called 'versionCount' that JBoss will use to implement optimistic locking via versioning.

jbosscmp_jdbc.xml
=============
This contains the CMP definition for the 'group' bean. It shows how to mapping the optimistic locking field to the database.

jboss.xml
=======
This defines a new container configuration that uses optimistic locking and also specifies that my 'group' bean should use it. I created this file a long time before 3.2 went gold so JBoss 3.2's standard-jboss.xml file might contain optimistic locking container configurations. I haven't checked.

TALEntityBean
==========
This just shows that I defined the versionCount fields in my entity bean as I do other CMP fields even though the versionCount field is defined differently in the jbosscmp-jdbc.xml file.

Hope this helps. Locking works for the most part except in the situation I mentioned in my previous post. Having said this. Without actually seeing any official JBoss documentation on optimistic locking (which, I hope, will be soon), I could be totally out to left field :-)

Good luck.

Darryl


Hmmmm.....it doesn't look like it's gonna let me attach my files. I'll paste them below. Sorry for the long post...




/* *"******************************************************************** */

-- table: securitygroup
create table security.securitygroup
(
grpid int4 primary key,
name varchar (60) unique,
description varchar (255),

-- Meta-data.
creationDate timestamp not null default current_timestamp,
modificationDate timestamp not null default current_timestamp,
createdBy text not null default current_user,
modifiedBy text not null default current_user,
versionCount int4 not null default 1
)
with oids;
comment on table security.securitygroup is 'table used to store information on security groups created by the user.';




<!-- SecurityGroup -->

<ejb-name>SecurityGroupEJB</ejb-name>
<table-name>security.view_securitygroup</table-name>
<cmp-field>
<field-name>groupId</field-name>
<column-name>grpId</column-name>
<not-null/>
</cmp-field>
<cmp-field>
<field-name>name</field-name>
<column-name>name</column-name>
<not-null/>
</cmp-field>
<cmp-field>
<field-name>description</field-name>
<column-name>description</column-name>
</cmp-field>
<cmp-field>
<field-name>creationDate</field-name>
<column-name>creationDate</column-name>
</cmp-field>
<cmp-field>
<field-name>modificationDate</field-name>
<column-name>modificationDate</column-name>
</cmp-field>
<cmp-field>
<field-name>createdBy</field-name>
<column-name>createdBy</column-name>
</cmp-field>
<cmp-field>
<field-name>modifiedBy</field-name>
<column-name>modifiedBy</column-name>
</cmp-field>
<optimistic-locking>
<version-column/>
<field-name>versionCount</field-name>
<column-name>versionCount</column-name>
<jdbc-type>INTEGER</jdbc-type>
<sql-type>INT4</sql-type>
</optimistic-locking>




<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE jboss PUBLIC
"-//JBoss//DTD JBOSS 3.2//EN"
"http://www.jboss.org/j2ee/dtd/jboss_3_2.dtd">





<enterprise-beans>

<ejb-name>SecurityGroupEJB</ejb-name>
<configuration-name>TalAdmin CMP 2.x EntityBean</configuration-name>

</enterprise-beans>


<container-configurations>

<!-- CMP 2.x EntityBean -->
<container-configuration extends="Standard CMP 2.x EntityBean">
<container-name>TalAdmin CMP 2.x EntityBean</container-name>
<locking-policy>org.jboss.ejb.plugins.lock.JDBCOptimisticLock</locking-policy>
<commit-option>A</commit-option>
</container-configuration>

</container-configurations>







package ca.talonline.business.ejb;

// Sun Java classes.
import java.io.*;
import java.util.*;
import javax.ejb.*;
import javax.naming.*;


/**
* Implements the methods used by most entity beans used by TAL Online. Methods
* include lifecycle methods, etc. Also implements the meta-data methods shared by
* all entity beans, such as version counts (for optimistic locking), timestamps
* (for auditing), etc.
*
* @author Darryl A. J. Staflund
*/
public abstract class TALEntityBean extends TALEnterpriseBean implements EntityBean
{
/**
* This entity bean's EntityContext.
*/
protected EntityContext entityContext;


/**
* Lifecycle method called by the EJB container when the entity bean is activated.
*/
public void ejbActivate ()
{
}


/**
* Lifecycle method called by the EJB container when the entity bean is loaded.
*/
public void ejbLoad ()
{
}


/**
* Lifecycle method called by the EJB container when the entity bean is passivated.
*/
public void ejbPassivate ()
{
}


/**
* Lifecycle method called by the EJB container when the entity bean is removed.
*/
public void ejbRemove ()
{
}


/**
* Lifecycle method called by the EJB container when the entity bean is stored.
*/
public void ejbStore ()
{
}


/**
* Called by the EJB container in order to pass the entity context to this entity bean.
*
* @param ctx The entity context of this entity bean.
*/
public void setEntityContext (EntityContext ctx)
{
this.entityContext = ctx;
}


/**
* Called by the EJB container in order to unset the entity context before the bean is removed.
*/
public void unsetEntityContext ()
{
this.entityContext = null;
}


/**
* Called when the entity bean wants the instance of the entity context.
*
* @return EntityContext The entity context of this entity bean.
*/
protected EntityContext getEntityContext ()
{
return (this.entityContext);
}


/**
* Increments the number of times this record has been modified. Is used to
* implement optimistic locking by JBoss.
*
* @param versionCount The new version count to assign to this bean.
*/
// public abstract void setVersionCount (Integer versionCount);


/**
* Returns the number of times this record has been modified. It is used to
* implement optimistic locking by JBoss.
*
* @return Integer The version count currently assigned to this bean.
*/
// public abstract Integer getVersionCount ();


/**
* Associates a creation date with the given entity bean.
*
* @param timestamp The creation date to associate with this entity bean.
*/
public abstract void setCreationDate (Date timestamp);


/**
* Returns the creation date of this entity bean.
*
* @return Date The creation date of this entity bean.
*/
public abstract Date getCreationDate ();


/**
* Associates a modification date with the given entity bean.
*
* @param timestamp The modification date to associate with this entity bean.
*/
public abstract void setModificationDate (Date timestamp);


/**
* Returns the modification date of this entity bean.
*
* @return Date The modification date of this entity bean.
*/
public abstract Date getModificationDate ();


/**
* Stores the username of the individual who first created this entity.
*
* @param username The name of the user who first created this entity.
*/
public abstract void setCreatedBy (String username);


/**
* Returns the username of the individual who first created this entity.
*
* @return String The name of the user who first created this entity.
*/
public abstract String getCreatedBy ();


/**
* Stores the username of the individual who last modified this entity.
*
* @param username The name of the user who last modified this entity.
*/
public abstract void setModifiedBy (String username);


/**
* Returns the username of the individual who last modified this entity.
*
* @return String The name of the user who last modified this entity.
*/
public abstract String getModifiedBy ();
}