Re: Locking stratergy of an Entity Bean in absence of transaction

Hi,
Adding one more question:
Now, apart from this concurrent access problem,The Bean locking can also occur
due to the high load?
Say, I have max number of possible instances of a Entitybean as 1000. but I am
processing 2000 records , from multiple clients. (Assume that it's a common routine
like a scheduler which gets executed for each client accessing the same set of
records), Is it that such a situation can lead to bean locking? If yes, Which
parameter needs to be tweaked? If I increase the bean instance parameter to 1500
(say changing maxBeansInCache to 2000 and maxBeansInFreePool to 40 (from 20) will
it have any performance problems? )
Thanks a lot for your response in Advance.
A summary of all the questions asked so far is attached herewith. Thank you again
for your time and patience to read and responding , in Advance.
Regards,
Nilesh.
"Nilesh" <[email protected]> wrote:
>
Hi,
Adding some more details:
To add:
The deployment descriptor provides option to mention the "isolationLevel"
. Might
be I have not understood/interpreted this correctly , If weblogic 4.5.1
uses only
Exclusive locking, then what is the use of mentioning isolation level
? Or might
be what this means is :
Generally weblogic uses mentioned transaction isolation level. Howver,
its in
case of concurrent users ONLY it uses pessimistic approach. i.e. say
Given two
users accessing the same row (say company based on company_id : we use
a separate
primary key class), only one will be allowed to commit at a time, the
row would
be exclusively locked by the first user.
Does custom primary key has anything to do with performance or bean
locking?
Thanks a lot in advance for answering.
Regards,
Nilesh.
Nilesh <[email protected]> wrote:
Agreed. In my case we are using webogic 4.5.1. However, assuming weblogic
used Pessimistic locking, Is there some way it can be tweaked? (say
to Optimistic locking), might be change some Transaction attribute in
Deployment descriptor ?
Some way?
[Bean Locking Questions.txt]

Similar Messages

NON-transactional session bean access entity bean

We are currently profiling our product using Borland OptmizeIt tool, and we
found some interesting issues. Due to our design, we have many session beans which
are non transactional, and these session beans will access entity beans to do
the reading operations, such as getWeight, getRate, since it's read only, there
is no need to do transaction commit stuff which really takes time, this could
be seen through the profile. I know weblogic support readonly entity bean, but
it seems that it only has benefit on ejbLoad call, my test program shows that
weblogic still creates local transaction even I specified it as transaction not
supported, and Transaction.commit() will always be called in postInvoke(), from
the profile, we got that for a single method call, such as getRate(), 80% time
spent on postInvoke(), any suggestion on this? BTW, most of our entity beans are
using Exclusive lock, that's the reason that we use non-transactional session
bean to avoid dead lock problem.
Thanks

Slava,
Thanks for the link, actually I read it before, and following is what I extracted
it from the doc:
<weblogic-doc>
Do not set db-is-shared to "false" if you set the entity bean's concurrency
strategy to the "Database" option. If you do, WebLogic Server will ignore the
db-is-shared setting.
</weblogic-doc>
Thanks
"Slava Imeshev" <[email protected]> wrote:
Hi Jinsong,
You may want to read this to get more detailed explanation
on db-is-shared (cache-between-transactions for 7.0):
http://e-docs.bea.com/wls/docs61/ejb/EJB_environment.html#1127563
Let me know if you have any questions.
Regards,
Slava Imeshev
"Jinsong HU" <[email protected]> wrote in message
news:[email protected]...
Thanks.
But it's still not clear to me in db-is-shared setting, if I specifiedentity
lock as database lock, I assumed db-is-shared is useless, because foreach
new
transaction, entity bean will reload data anyway. Correct me if I amwrong.
Jinsong
"Slava Imeshev" <[email protected]> wrote:
Jinsong,
See my answers inline.
"Jinsong Hu" <[email protected]> wrote in message
news:[email protected]...
Hi Slava,
Thanks for your reply, actually, I agree with you, we need to
review
our db
schema and seperate business logic to avoid db lock. I can not say,guys,
we need
to change this and that, since it's a big application and developedsince
EJB1.0
spec, I think they are afraid to do such a big change.Total rewrite is the worst thing that can happen to an app. The
better aproach would be identifying the most critical piece and
make a surgery on it.
Following are questions in my mind:
(1) I think there should be many companies using weblogic serverto
develop
large enterprise applications, I am just wondering what's the maintransaction/lock
mechanism that is used? Transional session / database lock,
db-is-shared
entity
I can't say for the whole community, as for my experience the standard
usage patthern is session fasades calling Entity EJBs while having
Required TX attribute plus plain transacted JDBC calls for bulk
reads or inserts.
is the dominant one? It seems that if you speficy database lock,
the
db-is-shared
should be true, right?Basically it's not true. One will need db-is-shared only if thereare
changes
to the database done from outside of the app server.
(2) For RO bean, if I specify read-idle-timeout to 0, it shouldonly
load
once at the first use time, right?I assume read-timeout-seconds was meant. That's right, but if
an application constantly reads new RO data, RO beans will be
constantly dropped from cache and new ones will be loaded.
You may want to looks at server console to see if there's a lot
of passivation for RO beans.
(3) For clustering part, have anyone use it in real enterpriseapplication?
My concern, since database lock is the only way to choose, how aboutthe
affect
of ejbLoad to performance, since most transactions are short live,if high
volume
transactions are in processing, I am just scared to death about
the
ejbLoad overhead.
ejbLoad is a part of bean's lifecycle, how would you be scared ofit?
If ejbLoads take too much time, it could be a good idea to profile
used SQLs. Right index optimization can make huge difference.
Also you may want cosider using CMP beans to let weblogic
take care about load optimization.
(4) If using Optimization lock, all the ejbStore need to do
version
check
or timestamp check, right? How about this overhead?As for optimistic concurrency, it performs quite well as you can
use lighter isolation levels.
HTH,
Slava Imeshev
"Jinsong Hu" <[email protected]> wrote in message
news:[email protected]...
We are using Exclusive Lock for entity bean, because of we do
not
want
to
load
data in each new transaction. If we use Database lock, that means
we
dedicate
data access calls to database, if database deadlock happens,
it's
hard
to
detect,
while using Exclusive lock, we could detect this dead lock in
container
level.
The problem is, using Exclusive concurrency mode you serialize
access to data represented by the bean. This aproach has negative
effect on ablity of application to process concurrent requests.As
a
result the app may have performance problems under load.
Actually, at the beginnning, we did use database lock and usingtransactional
The fact that you had database deadlocking issues tells that
application logic / database schema may need some review.
Normally to avoid deadlocking it's good to group database
operations mixing in updattes and inserts into one place so
that db locking sequence is not spreaded in time. Moving to
forced serialized data access just hides design/implementation
problems.
session bean, but the database dead lock and frequent ejbLoad
really
kill
us,
so we decided to move to use Exclusive lock and to avoid dead
lock,
we
change
some session bean to non-transactional.Making session beans non-transactions makes container
creating short-living transactions for each call to entity bean
methods. It's a costly process and it puts additional load to
both container and database.
We could use ReadOnly lock for some entity beans, but since weblogicserver will
always create local transaction for entity bean, and we found
transaction
commit
is expensive, I am arguing why do we need create container leveltransaction for
read only bean.First, read-only beans still need to load data. Also, you may seeRO
beans
contanly loading data if db-is-shared set to true. Other reason
can
be
that
RO semantics is not applicable the data presented by RO bean (forinstance,
you have a reporting engine that constantly produces "RO" data,
while
application-consumer of that data retrieves only new data and neverasks
for "old" data). RO beans are good when there is a relatively stable
data
accessed repeatedly for read only access.
You may want to tell us more about your app, we may be of help.
Regards,
Slava Imeshev
I will post the performance data, let's see how costful
transaction.commit
is.
"Cameron Purdy" <[email protected]> wrote:
We are currently profiling our product using Borland
OptmizeIt
tool,
and we
found some interesting issues. Due to our design, we have
many
session
beans which
are non transactional, and these session beans will access
entity
beans
to
do
the reading operations, such as getWeight, getRate, since
it's
read
only,
there
is no need to do transaction commit stuff which really takes
time,
this
could
be seen through the profile. I know weblogic support readonly
entity
bean,
but
it seems that it only has benefit on ejbLoad call, my test
program
shows
that
weblogic still creates local transaction even I specified
it
as
transaction not
supported, and Transaction.commit() will always be called
in
postInvoke(),
from
the profile, we got that for a single method call, such as
getRate(),
80%
time
spent on postInvoke(), any suggestion on this? BTW, most of
our
entity
beans are
using Exclusive lock, that's the reason that we use
non-transactional
session
bean to avoid dead lock problem.I am worried that you have made some decisions based on an improper
understand of what WebLogic is doing.
First, you say "non transactional", but from your description
you
should
have those marked as tx REQUIRED to avoid multiple transactions
(since
non-transactional just means that the database operation becomesits
own
little transaction).
Second, you say you are using exclusive lock, which you shouldonly
use
if
you are absolutely sure that you need it, (and note that it
does
not
work in
a cluster).
Peace,
Cameron Purdy
Tangosol, Inc.
http://www.tangosol.com/coherence.jsp
Tangosol Coherence: Clustered Replicated Cache for Weblogic
"Jinsong Hu" <[email protected]> wrote in message
news:[email protected]...
>

How to use same transaction when calling CMP entity beans and DAO (JDBC)

We are currently using Weblogic 8.1 SP2 with an Oracle 10g database (using XA thin and non-XA drivers).
We have a session bean that invokes an entity bean and a DAO (data access object pattern) in order to add data in 2 separate tables (account and history). Rows are added to the first (account) table using a CMP Entity bean while inserts are done in the 2nd (history) table using a DAO. Here is some pseudo code:
addHistorySessionBean (trans-attribute="Required")
begin
Step #1 - call addAccountEntityBean (trans- attribute="Required")
Step #2 - call addHistoryDAO (get datasource, connection)
end
The 2nd table (history) has a foreign key constraint to ensure that the corresponding key exists in the first (account) table. Unfortunately, DAO inserts on the 2nd (history) table fail with a foreign key constraint violation (INTEGRITY CONSTRAINT VIOLATION - PARENT KEY NOT FOUND!) since they cannot see the row added to the 1st (account) table in step #1 by the CMP entity bean.
How does one ensure that all this is done in a single transaction ? It appears that the app server creates two seperate transactions (one for the session bean facade and the entity bean and a 2nd transaction (when we retrieve a connection using the same data source JNDI name) for the DAO.
A post on server side suggested using a "<resource-ref>" in the session bean to tie the two potentially separate transactions together, but that does not work for us. However, I am not sure if we are doing that correctly. After we define the resource ref in the session facade bean, do we use the resource ref "name" attribute to lookup the datasource or do we still lookup the datasource by JNDI name ? Do we need to define the resource-ref tag in the entity bean also ?
Does Weblogic allow using a single transaction for this type of a scenario ? How does one specify within Weblogic that the same transaction should be utilized by the entity bean and any subsequent DAOs?
People have also suggested that we defer constraint checking until the transaction(s) are committed but that sounds like a work acount without addressing this issue. Would postponing the constraint checking in Oracle cause any additional overhead ?
Any suggestions with specific examples or documentation on how to address this issue will be gratefully appreciated.

Thanks for your suggestion. Unfortunately, this does not work since it appears that there are 2 separate transactions going on here. One, the original one initiated by the session bean and used by the entity bean and the other initiated by the DAO. Any other ideas appreciated.
Hi,
Try setting the delay-database-inserts tag to
ejbCreate in RDBMS descriptor file.
http://bernal/stage/wls/docs81/ejb/DDreference-cmp-jar
.html#1113981
vasanthi ramesh

Where to see the SQL statement that CMP Entity bean excuted?

hi, I'm wondering where I can find the SQL that a CMP entity bean executed in a transaction?
thank you!

You can do it in many ways. If you are using eclipse then using eclipse
plugins for weblogic you van do it. I have heard that in weblogic workshop
also you can do it. If the above do doesn;t solves your problem then check
this out.
http://www.p6spy.com/documentation/install.htm
Hope that helps.
<Xin Zhuang> wrote in message news:[email protected]..
hi, I'm wondering where I can find the SQL that a CMP entity bean executed
in a transaction?
thank you!

Use direct JDBC with CMP entity bean in one transaction

I am trying to use direct JDBC call with CMP entity bean within a session
bean method that requires transaction. The problem is that it appears these
are not in the same transaction. When I use the JDBC call, the CMP entity
bean update to the DB has not been committed yet.
We are using Weblogic 5.1 SP6. The DB is Oracle.
What I do for the JDBC is get a new connection from the pool using weblogic
jdbc pool driver.
Any help would be appreciated.
Patrick

Hi. You can do JDBC and invoke CMP EJBs and have this all treated
as one transaction, if your hand-written code explicitly starts
a JTS transaction, then uses the jts driver or a TxDataSource to
get the JDBC connection. Then your code can call transactional
EJBs and their work will be included in the transaction you started.
Assuming the bean work went OK, and your manual JDBC went OK, you
can manually commit the UserTransaction at that time. This is 5.1
talk. For 6.0, with @PC, this may be even easier...
Joe
Patrick Shen wrote:
>
But if I do that, then they would not be in the same transaction anymore.
Is there any way to use JDBC with CMP Entity bean in the same transaction?
Patrick
"L'artiste" <[email protected]> wrote in message
news:[email protected]...
Are you calling all the CMP create in the session Bean ? If so, beforeyou
make the JDBC call from the session bean, the CMP in 2. should commit. Try
to set its attribute to TX_REQUIRES_NEW. This way, the calling client will
block until this transaction is done (committed) before the execution
continues. There might be some overhead involved in doing so if you are
anticipating a lot of users.
"Patrick Shen" <[email protected]> wrote in message
news:[email protected]...
What I am trying to do is:
In a Session bean method -
1. create a new CMP entity bean (a new row in DB table)
2. create another new CMP entity bean that uses previous bean as foreignkey
3. use JDBC to update the row just created
And all these 3 calls have to be in one transaction.
Thanks,
Patrick
"L'artiste" <[email protected]> wrote in message
news:[email protected]...
Can you give a little bit more information?
Do you have methods in your session bean that creates this CMP entitybeans?
It looks like
you might wanna try to change the isolation level to
TRANSACTION_READ_COMITTED
to preven dirty_read.
"Patrick Shen" <[email protected]> wrote in message
news:[email protected]...
I am trying to use direct JDBC call with CMP entity bean within a
session
bean method that requires transaction. The problem is that it
appears
these
are not in the same transaction. When I use the JDBC call, the CMP
entity
bean update to the DB has not been committed yet.
We are using Weblogic 5.1 SP6. The DB is Oracle.
What I do for the JDBC is get a new connection from the pool usingweblogic
jdbc pool driver.
Any help would be appreciated.
Patrick
PS: Folks: BEA WebLogic is expanding rapidly, with both entry and advanced positions
for people who want to work with Java, XML, SOAP and E-Commerce infrastructure products.
We have jobs at Nashua NH, Liberty Corner NJ, San Francisco and San Jose CA.
Send resumes to [email protected]

How to Create and Remove CMP Entity with Toplink in same transaction??

Hi, i have a problem to create and delete cmp intances with toplink.
I create a entity bean and remove the same entity bean in the same transaction.
ie. my method have this code:
bean a = homeBean.create(pk);
a.remove();
bean a = homeBean.create(pk);
this code throws a javax.ejb.DuplicateKeyException
Toplink not remove CMP, execute the two calls of create first.
What configure toplink to support this case ??
Is this possible ??
I Can't controling the transaction manualy i'm using CMP entity beans with CMT.
tanks.
Message was edited by:
Carlos Lacerda

BM,
If you want to import the utils package into your code, then the location of the utils package has to be in your CLASSPATH. JDeveloper uses libraries to define a project's CLASSPATH.
I'm not sure exactly what's going on here, but you might want to read the information about packages and class libraries in the online documentation. It's under:
User Guides
-> Working with JDeveloper
-> Packages and Class Libraries
Blaise

Object locking of entity bean in a SSBean[Environment: WebLogic 10.0, EJB3.0, Kodo/OpenJPA]

Hello friends,
I am facing bottle neck with Object Locking for an Entity bean using OpenJPA Persistence Manager under Weblogic 10.0 application server deployments.
I want to block [ for the specific method ] entity bean being accessed from other client programs when they invoke common method in a Stateless Session EJB. Particularly, Consider the situation:
Client1: Modifying Customer entity with id: 100. Then I locked that entity using OpenJPA Entity Manager within the transaction block. And i entered that thread to sleep before committing the transaction.
At this time, started new thread, Client2: Modifying the same Customer entity with id:100. I expected this thread will be get blocked when control pass to the lock() method. But it doesn't happened. It goes through the line of codes and also put into sleep.
After thread sleep timeout, first thread Client1 commit successfully. But the second gets Rollback Exception due to optimistic lock exception occurring since customer entity is modified in another transaction.
This exception is occurred because of Database level concurrency control for optimistic locking in a weblogic server. Its default to weblogic.
But, what i expected is to assert lock at the object level, thereby the 2nd thread - Client2 will be blocked while Client1 is in the middle of a transaction and then Client2 use modified Customer entity . But it doesn't happened. I used Kodo Persistance Provider as Persistence Unit, OpenJPAEntityManager to do transaction, locking , finding and merging the entity bean.
Can anyone provide help to fine grain this object locking functionality ??? I look forward to your brilliant thoughts......
Rajesh KR
Geojit Technologies

Dear Chicon,
I made thread to sleep for checking the "Object Locking" functionality of OpenJPAEntityManager. My intention was to block the second thread when the first thread being locked when a concurrent access occurs. But it doesn't happened and code execution passed to thread sleep.
I mean when 2 client access the same entity at same time (in same milliseconds) , and what happens to 2nd thread when 1st thread locks the entity object.
I guarantee you that i started the 2nd thread before the 4sec time stamp given to the object locking. I tested it with a bigger timestamp, still it given concurrent blocking of the same entity bean.
My question is why the object locking is not working with concurrent access to same entity bean from more than one thread???
I think you get the correct question what i intended ????
Regards,
Raj...

EJB entity beans and BC4J

I have looked at BC4J and it looks good. Buy my question is that isn't this frame work in direct conflict with EJB entity beans. I know lot of stuff that is there in BC4J should have been in EJB enitiy beans, but as a developer why should I go with BC4J and not the standard EJB stuff considering the fact that BC4J is properietery to Oracle?Any thoughts?

Vimal,
Without going into exhaustive detail here, I would like to recommend that you take a look at the BC4J Technical White Paper available from the JDeveloper page on OTN (in the 3.0 Technical Information section):
http://technet.oracle.com/products/jdev/info/techwp20/wp.html
Amoung other things to note, BC4J is based on pure Java, and is what we consider a 'white box', meaning, you as a developer have complete control over what is going on. You can extend any of the code generated to customize it.
Primarily though, the major benefit of BC4J is that we have taken care of most of the complicated communication code for you. Communication between the client and the data server, transaction handling, row locking, etc are already written for you. You just use, extend, customize what we have provided.
In addition, BC4J allows you flexibility in your deployment environment decision. Regardless of where and how you deploy your BC4J Application Module, the client is unchanged.
Those are the key advantages. Again, for more details, I would take a look at the white paper to see if it more fully addresses your questions.

Proxy object and entity Bean interaction

Hello,
I'd like to have some precisions on the interactions between the proxy object (client) and the entity bean(server):
- does J2EE provides ways for a bean to manage clients, to define roles and permissions, lock, etc ... ? What informations an entity bean can know about the clients ?.
- how does the context mechanism work on the entity bean side ?
- how does an entity bean identify different clients ? how does it recognize one from another ? I mean if client c1 and client c2 use same entity bean B, how B can manage different roles for c1 and c2, and how can B returns specific values to a particular client.
Thx.

If you can read some tutorial, you will get all the information.
I'll suggest a book EJB by richard manson publicvations oreilly.
The activities you are talking about is responsibility of container and user developed bean are totally absytracted from this system level activities.
Primary service include security which take care of activities like Authentication, access control and secure communication.
for role based access control u have container providing the identity by Principal object. DDescriptors declare which logical roles are allowed to access even perticular method of the bean.

Problem in creating CMP Entity Bean - Pls Help

I am trying to build one simple project having jsps to get connected to CMP Entity Bean.
But while deploying I am getting the following error...
Nov 15, 2004 10:59:09... Info: End of log messages of the target system.
Nov 15, 2004 10:59:09... Info: ***** End of SAP J2EE Engine Deployment (J2EE Application) *****
Nov 15, 2004 10:59:09... Error: Execution of deployment action for "EntityCMPAppln" aborted:
Caught exception during application deployment from SAP J2EE Engine's deploy service:
java.rmi.RemoteException: Error occurred while starting application bcone.com/EntityCMPAppln and wait.
Reason: Complex error : server ID 6155350:Application bcone.com/EntityCMPAppln cannot be started, because it has hard reference to resource CONFIG_DB with type javax.sql.DataSource, but it is not active on the server.
(message ID: com.sap.sdm.serverext.servertype.inqmy.extern.EngineApplOnlineDeployerImpl.performAction(DeploymentActionTypes).REMEXC)
Nov 15, 2004 10:59:09... Error: Deployment NOT successful for EntityCMPAppln
Nov 15, 2004 10:59:09... Info: SDM configuration: Do not automatically start/stop J2EE Engine. Do not restore state of J2EE Engine now.
Nov 15, 2004 10:59:09... Error: -
At least one of the Deployments failed -
Nov 15, 2004 11:05:16... Info: Request for Logon as admin accepted
===========================================
Nov 15, 2004 11:05:08... Info: =   Starting to execute command 'remotegui'   =
Nov 15, 2004 11:05:08... Info: ===============================================
Nov 15, 2004 11:05:10... Info: SDM started successfully.
Please tell me how to activate the CONFIG_DB reference in database. Or what Extra I have to do to run this example.
Regards,
Vivek Ojha

Dear Benny,
The code of the required files is pasted below....
Application.XML
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE application PUBLIC "-//Sun Microsystems, Inc.//DTD J2EE Application 1.3//EN"
                             "http://java.sun.com/dtd/application_1_3.dtd">
<application>
    <display-name>EntityCMPAppln</display-name>
    <description>EAR description</description>
    <module>
        <ejb>EntityCMPEjb.jar</ejb>
    </module>
    <module>
        <web>
            <web-uri>EntityCMPWeb.war</web-uri>
            <context-root>/student</context-root>
        </web>
    </module>
</application>
Application-j2ee-engine.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE application-j2ee-engine SYSTEM "application-j2ee-engine.dtd">
<application-j2ee-engine>
     <provider-name>bcone.com</provider-name>
     <fail-over-enable
          mode="disable"/>
</application-j2ee-engine>
data-source-aliases.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE data-source-aliases SYSTEM "data-source-aliases.dtd">
<data-source-aliases>
     <aliases>
          <data-source-name>${com.sap.datasource.default}</data-source-name>
          <alias>STUDENTDB</alias>
     </aliases>
</data-source-aliases>
ejb-j2ee-engine.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ejb-j2ee-engine SYSTEM "ejb-j2ee-engine.dtd">
<ejb-j2ee-engine>
     <enterprise-beans>
          <enterprise-bean>
               <ejb-name>StudentBean</ejb-name>
               <resource-ref>
                    <res-ref-name>jdbc/STUDENTDB</res-ref-name>
                    <res-link>STUDENTDB</res-link>
               </resource-ref>
               <entity-props/>
          </enterprise-bean>
     </enterprise-beans>
</ejb-j2ee-engine>
ejb-jar.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
     <description>EJB JAR description</description>
     <display-name>EJB JAR</display-name>
     <enterprise-beans>
          <entity>
               <ejb-name>StudentBean</ejb-name>
               <home>com.bcone.ejb.StudentHome</home>
               <remote>com.bcone.ejb.Student</remote>
               <ejb-class>com.bcone.ejb.StudentBean</ejb-class>
               <persistence-type>Container</persistence-type>
               <prim-key-class>java.lang.String</prim-key-class>
               <reentrant>False</reentrant>
               <cmp-version>2.x</cmp-version>
               <abstract-schema-name>StudentBean</abstract-schema-name>
               <cmp-field>
                    <field-name>studentId</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>lname</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>standard</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>fyear</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>fname</field-name>
               </cmp-field>
               <primkey-field>studentId</primkey-field>
               <resource-ref>
                    <res-ref-name>jdbc/STUDENTDB</res-ref-name>
                    <res-type>javax.sql.DataSource</res-type>
                    <res-auth>Container</res-auth>
               </resource-ref>
          </entity>
     </enterprise-beans>
</ejb-jar>
persistent.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE persistent-ejb-map SYSTEM "persistent.dtd">
<persistent-ejb-map>
     <locking
          type="Table"/>
     <db-properties>
          <data-source-name>CONFIG_DB</data-source-name>
          <database-vendor
               name="SAPDB"/>
     </db-properties>
     <entity-beans>
          <entity-bean>
               <ejb-name>StudentBean</ejb-name>
               <table-name>TMP_STUDENTNEW</table-name>
               <field-map
                    key-type="PrimaryKey">
                    <field-name>studentId</field-name>
                    <column>
                         <column-name>STUDENTID</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>lname</field-name>
                    <column>
                         <column-name>LNAME</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>standard</field-name>
                    <column>
                         <column-name>STANDARD</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>fyear</field-name>
                    <column>
                         <column-name>FYEAR</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>fname</field-name>
                    <column>
                         <column-name>FNAME</column-name>
                    </column>
               </field-map>
          </entity-bean>
     </entity-beans>
     <relationships/>
</persistent-ejb-map>
StudentBean.java
package com.bcone.ejb;
import javax.ejb.EntityBean;
import javax.ejb.EntityContext;
import javax.ejb.RemoveException;
import javax.ejb.CreateException;
@abstractSchemaName StudentBean
@cmpVersion 2.x
@ejbHome <{com.bcone.ejb.StudentHome}>
@ejbPrimaryKey <{java.lang.String}>
@ejbRemote <{com.bcone.ejb.Student}>
@hasSimplePK true
public abstract class StudentBean implements EntityBean {
     public void ejbLoad() {
     public void ejbStore() {
     public void ejbRemove() throws RemoveException {
     public void ejbActivate() {
     public void ejbPassivate() {
     public void setEntityContext(EntityContext context) {
          myContext = context;
     public void unsetEntityContext() {
          myContext = null;
     private EntityContext myContext;
@primKeyField
     public abstract String getStudentId();
     public abstract void setStudentId(String studentId);
     public abstract String getLname();
     public abstract void setLname(String lname);
     public abstract String getFname();
     public abstract void setFname(String fname);
     public abstract String getStandard();
     public abstract void setStandard(String standard);
     public abstract String getFyear();
     public abstract void setFyear(String fyear);
Create Method.
     public String ejbCreate(
          String studentId,
          String fname,
          String lname,
          String standard,
          String fyear)
          throws CreateException {
          setStudentId(studentId);
          setFname(fname);
          setLname(lname);
          setStandard(standard);
          setFyear(fyear);
          return null;
Post Create Method.
     public void ejbPostCreate(
          String studentId,
          String fname,
          String lname,
          String standard,
          String fyear) {
          // TODO : Implement
StudentData.java
Created on Nov 14, 2004
To change the template for this generated file go to
Window>Preferences>Java>Code Generation>Code and Comments
package com.bcone.data;
@author Administrator
To change the template for this generated type comment go to
Window>Preferences>Java>Code Generation>Code and Comments
public class StudentData {
     private String studentId;
     private String fname;
     private String lname;
     private String standard;
     private String fyear;
@return
     public String getFname() {
          return fname;
@return
     public String getFyear() {
          return fyear;
@return
     public String getLname() {
          return lname;
@return
     public String getStandard() {
          return standard;
@return
     public String getStudentId() {
          return studentId;
@param string
     public void setFname(String string) {
          fname = string;
@param string
     public void setFyear(String string) {
          fyear = string;
@param string
     public void setLname(String string) {
          lname = string;
@param string
     public void setStandard(String string) {
          standard = string;
@param string
     public void setStudentId(String string) {
          studentId = string;
student.jsp
<%@ page language="java" %>
<html>
     <head>
          <title>
               Title
          </title>
     </head>
     <body>
          <form method="POST" action="WEBBOT-SELF" name="Student" onSubmit="">

<br>
<a href="/student/manageStudent.jsp?action=add" method="post"> Create </a>
<a href="/student/manageStudent.jsp?action=modify" method="post"> Modify </a>
<a href="/student/manageStudent.jsp?action=delete" method="post"> Delete </a>
<br><br>
<table border="1" width="32%">
    <tr>
      <td width="39%">Student ID </td>
      <td width="61%"><input type="text" name="studentId" size="20"></td>
    </tr>
    <tr>
      <td width="39%">First Name</td>
      <td width="61%"><input type="text" name="fname" size="20"></td>
    </tr>
    <tr>
      <td width="39%">Last Name</td>
      <td width="61%"><input type="text" name="lname" size="20"></td>
    </tr>
    <tr>
      <td width="39%">Standard</td>
      <td width="61%"><input type="text" name="standard" size="20"></td>
    </tr>
    <tr>
      <td width="39%">Fiscal Year</td>
      <td width="61%"><input type="text" name="fyear" size="20"></td>
    </tr>
    <tr>
      <td width="39%" align="center"><input type="submit" value="Submit" name="submit"></td>
      <td width="61%" align="center"><input type="reset" value="Reset" name="reset"></td>
    </tr>
</table>
</form>
     </body>
</html>
mamageStudent.jsp
<%@ page language="java"
import="javax.naming.,java.sql.,javax.sql,com.bcone.ejb."
%>
<html>
     <head>
          <title>
               Manage Student
          </title>
     </head>
     <body>
          <h1>
          </h1>
<jsp:useBean id="stu" class="com.bcone.data.StudentData" ></jsp:useBean>
<jsp:setProperty name="stu" property="*" />
<%
try {
     InitialContext ctx = new InitialContext();
     StudentHome home = (StudentHome) ctx.lookup("java:comp/env/StudentBean");
     String str = request.getParameter("action");
     if("action".equals(str)) {
          Student rem = home.create(remote.setFname(stu.getStudentId(),stu.getFname(),stu.getLname(),stu.getStandard(),stu.getFyear());
          out.println(stu.getStudentId() + "Student Created");
     } else if ("modify".equals(str)) {
          Student remote = home.findByPrimaryKey(stu.getStudentId());
          remote.setFname(stu.getFname());
          remote.setFname(stu.getLname());
          remote.setFname(stu.getStandard());
          remote.setFname(stu.getFyear());
          out.println(stu.getStudentId() + "Student modified");
     } else if ("delete".equals(str)) {
          Student stu1 = home.findByPrimaryKey(stu.getStudentId());
          stu1.remove();
          out.println(stu.getStudentId() + "Student deleted");
} catch (Exception e) {
     out.println("Exception e"+e.toString());
%>
     </body>
</html>
Regards,
Vivek Ojha

Can Entity Bean with Home Business Method replace Stateless Session Bean?

Since Entity Bean can have business methods in the Home Interface, can we use Entity Bean with Home Business Methods to replace Stateless Session Bean?
I am assuming we can get better performance by doing this since the overhead of creating Component Object can be avoided as compared to stateless session beans.

Requires-new makes the container start a new transaction. Only use that flag
          at the point that you are certain that a NEW transaction should BEGIN. I
          suggest you use Required as your default for all methods in the application,
          and only change that to anything else when you are certain that you should.
          Peace,
          Cameron Purdy
          Tangosol Inc.
          << Tangosol Server: How Weblogic applications are customized >>
          << Download now from http://www.tangosol.com/download.jsp >>
          "A.J,LEE" <[email protected]> wrote in message
          news:3ba5adb2$[email protected]..
          >
          > I find it result in "dead lock"
          > when I call RequiresNew attributed CMP method in session Bean.
          > Then, Is it possible to use CMP which is set with "RequiresNew"
          transaction attribute?
          >
          > I Wonder why.
          >
          > Thanx in advance.

Are EJB ( entity beans) are cached ?

Are EJB ( entity beans) are cached ?
I have a doubt here . As per my understanding , the entity beans are cached from the database. In that case , If I delete a row in the database by an external application ( say using TOAD tool) , how the Entity bean will be updated / reloaded ? Entity bean will be out of sync then .
Application server : weblogic/webspehere .

>
You can use the refresh method of the EntityManager interface to read new values from the database (if you expect it to be out of sync), and use locks to prevent others from changing your data while the application is performing actions in a transaction.Did you mean I have to write code for this ? can't be made it automatic refresh by the container ? Is there any settings I can configure so that container can do it by itself proactively ?
Also, using locks ...is this a container settings or I need to configure myself in ejb-jar.xml ? Could you please shed some light here ?

Using JDO under BMP entity beans

I have an entity bean that is a BMP which uses JDO under the hood. The Oc4J document says that "Bean-managed persistence entity beans manage the resource locking within the bean implementation themselves" in the advanced subject chapter. Ok can someone in oracle add an extra line eloborating on that statement ?
I am stuck in trying to pass a test that can do concurrent modify of an entity bean. I had 2 or more threads trying to modify one single BMP entity bean object concurrently. The database vendor recognizes one bean had the lock and deny locks to any other beans. Who should block the call to the database until one thread releases the lock on the object ? The developer ? J2EE container ? Database ?
J2EE tenet "Developers are shielded from concurrency and threading issues while implementing business logic" Does that still hold ??
An object Person's salary value and his benefit information are tried to be modified at the same time by different external system(salary administrator, benefit's administrator). But I dont want the user to see the lock on the object error, but instead I require a pessimistic lock on the BMP. Why does Oc4J not support pessimistic concurrency option for BMP ?

Kurien,
If you wish to bring something to the attention of the "Oracle dev team", I suggest you try Oracle's "MetaLink" Web site:
http://metalink.oracle.com
It is the official Oracle support Web site.
These forums are for the Oracle community. Oracle Corporation employees are not obliged to even visit these forums.
By the way, I am not an Oracle employee.
Good Luck,
Avi.
P.S. For your information, you may find Debu Panda's blogs of help:
http://radio.weblogs.com/0135826/

Help! My database connection from BMP Entity bean dies after a while!!!

Hi all!
I posted a related post about this lately How do I use connection pooling from BMP Entity Beans in OC4J 10.1.2? but it didn't solve my problems.
I have some entity beans coded with BMP, so I handle all database stuff myself. I have set up datasources.xml like this:
    <data-source
        class="com.evermind.sql.DriverManagerDataSource"
        name="OracleDS"
        location="jdbc/OracleCoreDS"
        xa-location="jdbc/xa/OracleXADS"
        ejb-location="jdbc/OracleDS"
        connection-driver="oracle.jdbc.driver.OracleDriver"
        username="scott"
        password="tiger"
        url="jdbc:oracle:thin:@//URL TO DB:SID"
        inactivity-timeout="30"
        min-connections="10"
        max-connections="50"
    />All JNDI connection lookup is done through the ejb-location as I should. I have been through all my try {} catch {} finally {} blocks, so ensure that I close all objects after use.
After a few hours of inactivity, my program dies. I have inserted a lot of debug statements (System.out.println()), and it seems like the program hangs when it's trying to execute a PreparedStatement.
I.e. it dies when I do ps.ExecuteQuery in the code below (NOTE: to make things easier to read, I have stripped out all error handling here):
    Context ic = new InitialContext();
    DataSource ds = (DataSource)ic.lookup("jdbc/OracleDS");
    c = ds.getConnection();
    System.out.println("DEBUG: Got database connection.");
    PreparedStatement ps = c.prepareStatement("SELECT foobar FROM footable WHERE foo=?");
    System.out.println("DEBUG: Prepared SQL statement.");
    ps.setString(1,"foo");
    ResultSet rs = ps.executeQuery();
    // Close all objects (rs, ps, c) here.My database is on another physical server, so I wonder if this is caused by an unstable network, or?
Please help!
~Morten

Hi again!
Sorry for the delay, but I have been busy lately.
Anyway: Our application server is 10.1.2, so I don't think patch 4307303 is relevant here. Database server is Oracle 9.2.0.6. Everything runs on Linux (of course) ;-).
Here's a thread dump:
Full thread dump Java HotSpot(TM) Server VM (1.4.2_04-b05 mixed mode):
"ApplicationServerThread-8" prio=1 tid=0x089a9448 nid=0x5902 in Object.wait() [885e6000..885e687c]
     at java.lang.Object.wait(Native Method)
     at EDU.oswego.cs.dl.util.concurrent.SynchronousChannel.poll(SynchronousChannel.java:353)
     - locked <0x91a31e60> (a EDU.oswego.cs.dl.util.concurrent.LinkedNode)
     at EDU.oswego.cs.dl.util.concurrent.PooledExecutor.getTask(PooledExecutor.java:767)
     at com.evermind.util.ReleasableResourcePooledExecutor.myGetTask(ReleasableResourcePooledExecutor.java:151)
     at com.evermind.util.ReleasableResourcePooledExecutor.access$000(ReleasableResourcePooledExecutor.java:33)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:190)
     at java.lang.Thread.run(Thread.java:534)
"AJPRequestHandler-ApplicationServerThread-7" prio=1 tid=0x08d78a58 nid=0x5902 runnable [8b2f4000..8b2f587c]
     at java.net.SocketInputStream.socketRead0(Native Method)
     at java.net.SocketInputStream.read(SocketInputStream.java:129)
     at oracle.net.ns.Packet.receive(Unknown Source)
     at oracle.net.ns.DataPacket.receive(Unknown Source)
     at oracle.net.ns.NetInputStream.getNextPacket(Unknown Source)
     at oracle.net.ns.NetInputStream.read(Unknown Source)
     at oracle.net.ns.NetInputStream.read(Unknown Source)
     at oracle.net.ns.NetInputStream.read(Unknown Source)
     at oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:978)
     at oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:950)
     at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:434)
     at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:181)
     at oracle.jdbc.driver.T4CPreparedStatement.execute_for_describe(T4CPreparedStatement.java:661)
     at oracle.jdbc.driver.OracleStatement.execute_maybe_describe(OracleStatement.java:959)
     at oracle.jdbc.driver.T4CPreparedStatement.execute_maybe_describe(T4CPreparedStatement.java:693)
     at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1065)
     at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:2901)
     at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:2942)
     - locked <0x914cad08> (a oracle.jdbc.driver.T4CPreparedStatement)
     - locked <0x920256c0> (a oracle.jdbc.driver.T4CConnection)
     at com.evermind.sql.FilterPreparedStatement.executeQuery(FilterPreparedStatement.java:270)
     at com.evermind.sql.FilterPreparedStatement.executeQuery(FilterPreparedStatement.java:270)
     at com.evermind.sql.PreparedStatementBCELProxy.executeQuery(PreparedStatementBCELProxy.java:31)
     at com.brunata.servicerapport.ejb.CustomerBean.ejbCreate(Unknown Source)
     at CustomerLocalHome_EntityHomeWrapper2.create(CustomerLocalHome_EntityHomeWrapper2.java:420)
     at com.brunata.servicerapport.BeanFactory.getCustomerBean(Unknown Source)
     at com.brunata.servicerapport.CustomerOpenAction.execute(Unknown Source)
     at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
     at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
     at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
     at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
     at com.evermind.server.http.ResourceFilterChain.doFilter(ResourceFilterChain.java:65)
     at com.brunata.servicerapport.CustomerAuthorizationFilter.doFilter(Unknown Source)
     at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:649)
     at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:322)
     at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:790)
     at com.evermind.server.http.AJPRequestHandler.run(AJPRequestHandler.java:208)
     at com.evermind.server.http.AJPRequestHandler.run(AJPRequestHandler.java:125)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
     at java.lang.Thread.run(Thread.java:534)
"Thread-23" daemon prio=1 tid=0x092ebb18 nid=0x5902 in Object.wait() [88565000..8856587c]
     at java.lang.Object.wait(Native Method)
     - waiting on <0x920000f0> (a java.util.TaskQueue)
     at java.util.TimerThread.mainLoop(Timer.java:429)
     - locked <0x920000f0> (a java.util.TaskQueue)
     at java.util.TimerThread.run(Timer.java:382)
"Thread-22" daemon prio=1 tid=0x092eb988 nid=0x5902 in Object.wait() [8dfa0000..8dfa087c]
     at java.lang.Object.wait(Native Method)
     - waiting on <0x92000188> (a java.util.TaskQueue)
     at java.util.TimerThread.mainLoop(Timer.java:429)
     - locked <0x92000188> (a java.util.TaskQueue)
     at java.util.TimerThread.run(Timer.java:382)
"AJPRequestHandler-ApplicationServerThread-6" prio=1 tid=0x08c03240 nid=0x5902 runnable [8b0f1000..8b0f187c]
     at java.net.SocketInputStream.socketRead0(Native Method)
     at java.net.SocketInputStream.read(SocketInputStream.java:129)
     at com.evermind.io.SingleReadBufferInputStream.readChunk(SingleReadBufferInputStream.java:116)
     at com.evermind.io.SingleReadBufferInputStream.read(SingleReadBufferInputStream.java:35)
     at com.evermind.server.http.AJPRequestHandler.readAJPPackets(AJPRequestHandler.java:462)
     at com.evermind.server.http.AJPRequestHandler.initRequest(AJPRequestHandler.java:396)
     at com.evermind.server.http.AJPRequestHandler.run(AJPRequestHandler.java:185)
     at com.evermind.server.http.AJPRequestHandler.run(AJPRequestHandler.java:125)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
     at java.lang.Thread.run(Thread.java:534)
"DestroyJavaVM" prio=1 tid=0x08053278 nid=0x5902 waiting on condition [0..bfffcac4]
"OC4JMonitorThread" daemon prio=1 tid=0x08d7a5a0 nid=0x5902 in Object.wait() [88667000..8866787c]
     at java.lang.Object.wait(Native Method)
     - waiting on <0x92aed1f8> (a java.lang.Object)
     at oracle.ons.NotificationQueue.internalDequeue(NotificationQueue.java:253)
     - locked <0x92aed1f8> (a java.lang.Object)
     at oracle.ons.NotificationQueue.dequeue(NotificationQueue.java:226)
     at oracle.ons.Subscriber.receive(Subscriber.java:136)
     at com.evermind.server.OC4JMonitorThread.run(OC4JMonitorThread.java:315)
     at java.lang.Thread.run(Thread.java:534)
"Thread-6" daemon prio=1 tid=0x087f9f98 nid=0x5902 in Object.wait() [886e8000..886e887c]
     at java.lang.Object.wait(Native Method)
     - waiting on <0x92aed368> (a java.lang.Object)
     at java.lang.Object.wait(Object.java:429)
     at oracle.ons.NotificationQueue.internalDequeue(NotificationQueue.java:255)
     - locked <0x92aed368> (a java.lang.Object)
     at oracle.ons.NotificationQueue.dequeue(NotificationQueue.java:215)
     at oracle.ons.SenderThread.run(SenderThread.java:81)
"Thread-5" daemon prio=1 tid=0x087f9d10 nid=0x5902 runnable [88769000..8876987c]
     at java.net.SocketInputStream.socketRead0(Native Method)
     at java.net.SocketInputStream.read(SocketInputStream.java:129)
     at oracle.ons.InputBuffer.readMoreData(InputBuffer.java:267)
     at oracle.ons.InputBuffer.getNextString(InputBuffer.java:222)
     at oracle.ons.ReceiverThread.run(ReceiverThread.java:228)
"TaskManager" prio=1 tid=0x087f9b30 nid=0x5902 waiting on condition [887ea000..887ea87c]
     at java.lang.Thread.sleep(Native Method)
     at com.evermind.util.TaskManager.run(TaskManager.java:247)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:186)
     at java.lang.Thread.run(Thread.java:534)
"Thread-4" prio=1 tid=0x08ca2fb8 nid=0x5902 in Object.wait() [891e2000..891e287c]
     at java.lang.Object.wait(Native Method)
     - waiting on <0x92aee258> (a java.util.TaskQueue)
     at java.util.TimerThread.mainLoop(Timer.java:429)
     - locked <0x92aee258> (a java.util.TaskQueue)
     at java.util.TimerThread.run(Timer.java:382)
"AJPConnectionListener [0.0.0.0/0.0.0.0:3302]" prio=1 tid=0x086f1668 nid=0x5902 runnable [8a7ca000..8a7ca87c]
     at java.net.PlainSocketImpl.socketAccept(Native Method)
     at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:353)
     - locked <0x927a0390> (a java.net.PlainSocketImpl)
     at java.net.ServerSocket.implAccept(ServerSocket.java:448)
     at java.net.ServerSocket.accept(ServerSocket.java:419)
     at com.evermind.server.http.AJPConnectionListener.run(AJPConnectionListener.java:60)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:186)
     at java.lang.Thread.run(Thread.java:534)
"RMIServer [0.0.0.0:3202] count:2" prio=1 tid=0x086cbff0 nid=0x5902 runnable [8b172000..8b17287c]
     at java.net.PlainSocketImpl.socketAccept(Native Method)
     at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:353)
     - locked <0x927a0850> (a java.net.PlainSocketImpl)
     at java.net.ServerSocket.implAccept(ServerSocket.java:448)
     at java.net.ServerSocket.accept(ServerSocket.java:419)
     at com.evermind.server.rmi.RMIServer.run(RMIServer.java:464)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:186)
     at java.lang.Thread.run(Thread.java:534)
"JMSServer[webprod:3702]" prio=1 tid=0x0879aff0 nid=0x5902 runnable [8b1f3000..8b1f387c]
     at java.net.PlainSocketImpl.socketAccept(Native Method)
     at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:353)
     - locked <0x92746aa0> (a java.net.PlainSocketImpl)
     at java.net.ServerSocket.implAccept(ServerSocket.java:448)
     at java.net.ServerSocket.accept(ServerSocket.java:419)
     at com.evermind.server.jms.JMSServer.run(JMSServer.java:516)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:186)
     at java.lang.Thread.run(Thread.java:534)
"LogFlusher" daemon prio=1 tid=0x081b91a0 nid=0x5902 waiting on condition [8b274000..8b27487c]
     at java.lang.Thread.sleep(Native Method)
     at oracle.core.ojdl.BufferedLogWriter$Flusher.run(BufferedLogWriter.java:354)
"Signal Dispatcher" daemon prio=1 tid=0x080ba9e0 nid=0x5902 waiting on condition [0..0]
"Finalizer" daemon prio=1 tid=0x080b61a8 nid=0x5902 in Object.wait() [8e9a7000..8e9a787c]
     at java.lang.Object.wait(Native Method)
     at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:111)
     - locked <0x925b0378> (a java.lang.ref.ReferenceQueue$Lock)
     at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:127)
     at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)
"Reference Handler" daemon prio=1 tid=0x080b5dc8 nid=0x5902 in Object.wait() [8ea28000..8ea2887c]
     at java.lang.Object.wait(Native Method)
     at java.lang.Object.wait(Object.java:429)
     at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:115)
     - locked <0x925b02a0> (a java.lang.ref.Reference$Lock)
"VM Thread" prio=1 tid=0x080b52e0 nid=0x5902 runnable
"VM Periodic Task Thread" prio=1 tid=0x080bee08 nid=0x5902 waiting on condition
"Suspend Checker Thread" prio=1 tid=0x080b9fc8 nid=0x5902 runnable As far as I can see, my PreparedStatement (or connection) is locked.... Any ideas?
~Morten ;-)

Entity beans caching non-persistent data between transactions

Some of the properties in our entity bean implementation classes are not declared
in our descriptor files, and therefore, are non-persistent (we are using container-managed
persistence); I will refer to these properties as "non-persistent properties".
In WebLogic 5.1, we've noticed that the non-persistent properties are cached in
between transactions. For instance, I ask for a particular Person (Person(James)),
and I set one of the non-persistent properties (Property(X)) inside Transaction(A).
In Transaction(B) (which is exclusive of Transaction(A)), I access Property(X)
and find that it is the same value as I had set in Transaction(A)- this gives
the appearance that non-persistent entity properties are being cached in between
transactions.
The same appears to hold true in WebLogic 7 SP1, however, we must use the "Exclusive"
concurrency-strategy to maintain this consistency.
I am worried that this assumption we are making of non-persistent properties is
not valid in all cases, and the documentation does not promise anything in the
way of such an assumption. I am worried that the container could kill the Person(James)
entity implementation instance in the pool after Transaction(A), and create a
new Person(James) instance to serve Transaction(B)- once that happens our assumption
fails.
"Database" concurrency strategy seems to fail our assumption on a regular basis,
but that makes sense, since the documentation states that the "database will maintain
the cache", and the container seems more willing to kill instances when they are
finished with, or create new instances for new transactions.
So my question is this: What is exactly guaranteed by the "Exclusive" concurrency-strategy?
Will the assumption that we've made above ever fail under this strategy?
Thanks in advance for any help.
Regards,
James

It simply means that there is only one entity bean instance per PK in the
server, and transaction which uses it locks it exclusively.
James DeFelice <[email protected]> wrote:
Thank you for the suggestion. I have considered taking this path, but before I
make a final decision, I was hoping to get a clear answer to the question that
I stated below:
What EXACTLY is guaranteed by the "Exclusive" concurrency-strategy? Maybe someone
from BEA knows?
"Cameron Purdy" <[email protected]> wrote:
To be safe: You should clear those values before the ejb load or set
them
after (or both).
Peace,
Cameron Purdy
Tangosol, Inc.
http://www.tangosol.com/coherence.jsp
Tangosol Coherence: Clustered Replicated Cache for Weblogic
"James DeFelice" <[email protected]> wrote in message
news:[email protected]...
Some of the properties in our entity bean implementation classes arenot
declared
in our descriptor files, and therefore, are non-persistent (we areusing
container-managed
persistence); I will refer to these properties as "non-persistentproperties".
In WebLogic 5.1, we've noticed that the non-persistent properties arecached in
between transactions. For instance, I ask for a particular Person(Person(James)),
and I set one of the non-persistent properties (Property(X)) insideTransaction(A).
In Transaction(B) (which is exclusive of Transaction(A)), I accessProperty(X)
and find that it is the same value as I had set in Transaction(A)-this
gives
the appearance that non-persistent entity properties are being cachedin
between
transactions.
The same appears to hold true in WebLogic 7 SP1, however, we must usethe
"Exclusive"
concurrency-strategy to maintain this consistency.
I am worried that this assumption we are making of non-persistentproperties is
not valid in all cases, and the documentation does not promise anythingin
the
way of such an assumption. I am worried that the container could killthe
Person(James)
entity implementation instance in the pool after Transaction(A), andcreate a
new Person(James) instance to serve Transaction(B)- once that happensour
assumption
fails.
"Database" concurrency strategy seems to fail our assumption on a regularbasis,
but that makes sense, since the documentation states that the "databasewill maintain
the cache", and the container seems more willing to kill instanceswhen
they are
finished with, or create new instances for new transactions.
So my question is this: What is exactly guaranteed by the "Exclusive"concurrency-strategy?
Will the assumption that we've made above ever fail under this strategy?
Thanks in advance for any help.
Regards,
James
Dimitri

Re: Locking stratergy of an Entity Bean in absence of transaction

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