Entity Bean Database Access Problem

I have developed the CustomerBook application from the NetBeans 4.1 quick start tutorial with SJAS8.1Q2 (http://www.netbeans.org/kb/41/quickstart-j2ee.html) with MySQL. I get the following set of errors. I am new to SJAS. I've tried a lot of different things. For the life of me, I can't understand why this isn't working. I know the problem is with the entity bean accessing the database because the session bean communicates well with the client when calling the entity bean.
Thank you in advance for any efforts made to help me on this.
Seymour
[#|2005-08-15T15:58:50.250-0500|INFO|sun-appserver-pe8.1_02|javax.enterprise.system.container.ejb|_ThreadID=21;|EJB5018: An exception was thrown during an ejb invocation on [CustomerFacadeBean]|#]
[#|2005-08-15T15:58:50.251-0500|INFO|sun-appserver-pe8.1_02|javax.enterprise.system.container.ejb|_ThreadID=21;|
javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean; nested exception is: com.sun.jdo.api.persistence.support.JDOFatalInternalException: JDO76519: Failed to identify vendor type for the data store.
NestedException: java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : org.gjt.mm.mysql.jdbc2.optional.MysqlDataSource
com.sun.jdo.api.persistence.support.JDOFatalInternalException: JDO76519: Failed to identify vendor type for the data store.
NestedException: java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : org.gjt.mm.mysql.jdbc2.optional.MysqlDataSource
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.initializeSQLStoreManager(SQLPersistenceManagerFactory.java:870)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.getFromPool(SQLPersistenceManagerFactory.java:786)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.getPersistenceManager(SQLPersistenceManagerFactory.java:673)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.PersistenceManagerFactoryImpl.getPersistenceManager(PersistenceManagerFactoryImpl.java:849)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.PersistenceManagerFactoryImpl.getPersistenceManager(PersistenceManagerFactoryImpl.java:681)
     at ejb.CustomersBean_2122496195_ConcreteImpl.jdoGetPersistenceManager(CustomersBean_2122496195_ConcreteImpl.java:862)
     at ejb.CustomersBean_2122496195_ConcreteImpl.ejbFindByPrimaryKey(CustomersBean_2122496195_ConcreteImpl.java:417)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.enterprise.security.SecurityUtil.invoke(SecurityUtil.java:147)
     at com.sun.ejb.containers.EntityContainer.invokeFindByPrimaryKey(EntityContainer.java:738)
     at com.sun.ejb.containers.EJBLocalHomeInvocationHandler.invoke(EJBLocalHomeInvocationHandler.java:181)
     at $Proxy15.findByPrimaryKey(Unknown Source)
     at ejb.CustomerFacadeBean.getCompanyInfo(CustomerFacadeBean.java:73)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.enterprise.security.SecurityUtil$2.run(SecurityUtil.java:153)
     at java.security.AccessController.doPrivileged(Native Method)
     at com.sun.enterprise.security.application.EJBSecurityManager.doAsPrivileged(EJBSecurityManager.java:950)
     at com.sun.enterprise.security.SecurityUtil.invoke(SecurityUtil.java:158)
     at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:128)
     at $Proxy18.getCompanyInfo(Unknown Source)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie._invoke(ReflectiveTie.java:123)
     at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(CorbaServerRequestDispatcherImpl.java:648)
     at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(CorbaServerRequestDispatcherImpl.java:192)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(CorbaMessageMediatorImpl.java:1709)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:1569)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleInput(CorbaMessageMediatorImpl.java:951)
     at com.sun.corba.ee.impl.protocol.giopmsgheaders.RequestMessage_1_2.callback(RequestMessage_1_2.java:181)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:721)
     at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.dispatch(SocketOrChannelConnectionImpl.java:469)
     at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.doWork(SocketOrChannelConnectionImpl.java:1258)
     at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.run(ThreadPoolImpl.java:409)
NestedStackTrace:
java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : org.gjt.mm.mysql.jdbc2.optional.MysqlDataSource
     at com.sun.gjc.spi.DataSource.getConnection(DataSource.java:74)
     at com.sun.jdo.spi.persistence.support.sqlstore.ejb.TransactionHelperImpl.getConnection(TransactionHelperImpl.java:181)
     at com.sun.jdo.spi.persistence.support.sqlstore.ejb.EJBHelper.getConnection(EJBHelper.java:166)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.getConnection(SQLPersistenceManagerFactory.java:892)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.initializeSQLStoreManager(SQLPersistenceManagerFactory.java:857)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.getFromPool(SQLPersistenceManagerFactory.java:786)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.SQLPersistenceManagerFactory.getPersistenceManager(SQLPersistenceManagerFactory.java:673)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.PersistenceManagerFactoryImpl.getPersistenceManager(PersistenceManagerFactoryImpl.java:849)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.PersistenceManagerFactoryImpl.getPersistenceManager(PersistenceManagerFactoryImpl.java:681)
     at ejb.CustomersBean_2122496195_ConcreteImpl.jdoGetPersistenceManager(CustomersBean_2122496195_ConcreteImpl.java:862)
     at ejb.CustomersBean_2122496195_ConcreteImpl.ejbFindByPrimaryKey(CustomersBean_2122496195_ConcreteImpl.java:417)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.enterprise.security.SecurityUtil.invoke(SecurityUtil.java:147)
     at com.sun.ejb.containers.EntityContainer.invokeFindByPrimaryKey(EntityContainer.java:738)
     at com.sun.ejb.containers.EJBLocalHomeInvocationHandler.invoke(EJBLocalHomeInvocationHandler.java:181)
     at $Proxy15.findByPrimaryKey(Unknown Source)
     at ejb.CustomerFacadeBean.getCompanyInfo(CustomerFacadeBean.java:73)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.enterprise.security.SecurityUtil$2.run(SecurityUtil.java:153)
     at java.security.AccessController.doPrivileged(Native Method)
     at com.sun.enterprise.security.application.EJBSecurityManager.doAsPrivileged(EJBSecurityManager.java:950)
     at com.sun.enterprise.security.SecurityUtil.invoke(SecurityUtil.java:158)
     at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:128)
     at $Proxy18.getCompanyInfo(Unknown Source)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie._invoke(ReflectiveTie.java:123)
     at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(CorbaServerRequestDispatcherImpl.java:648)
     at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(CorbaServerRequestDispatcherImpl.java:192)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(CorbaMessageMediatorImpl.java:1709)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:1569)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleInput(CorbaMessageMediatorImpl.java:951)
     at com.sun.corba.ee.impl.protocol.giopmsgheaders.RequestMessage_1_2.callback(RequestMessage_1_2.java:181)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:721)
     at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.dispatch(SocketOrChannelConnectionImpl.java:469)
     at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.doWork(SocketOrChannelConnectionImpl.java:1258)
     at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.run(ThreadPoolImpl.java:409)
javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean; nested exception is: com.sun.jdo.api.persistence.support.JDOFatalInternalException: JDO76519: Failed to identify vendor type for the data store.
NestedException: java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : org.gjt.mm.mysql.jdbc2.optional.MysqlDataSource
     at com.sun.ejb.containers.BaseContainer.checkExceptionClientTx(BaseContainer.java:2674)
     at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:2526)
     at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:819)
     at com.sun.ejb.containers.EJBLocalHomeInvocationHandler.invoke(EJBLocalHomeInvocationHandler.java:199)
     at $Proxy15.findByPrimaryKey(Unknown Source)
     at ejb.CustomerFacadeBean.getCompanyInfo(CustomerFacadeBean.java:73)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.enterprise.security.SecurityUtil$2.run(SecurityUtil.java:153)
     at java.security.AccessController.doPrivileged(Native Method)
     at com.sun.enterprise.security.application.EJBSecurityManager.doAsPrivileged(EJBSecurityManager.java:950)
     at com.sun.enterprise.security.SecurityUtil.invoke(SecurityUtil.java:158)
     at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:128)
     at $Proxy18.getCompanyInfo(Unknown Source)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at com.sun.corba.ee.impl.presentation.rmi.ReflectiveTie._invoke(ReflectiveTie.java:123)
     at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(CorbaServerRequestDispatcherImpl.java:648)
     at com.sun.corba.ee.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(CorbaServerRequestDispatcherImpl.java:192)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(CorbaMessageMediatorImpl.java:1709)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:1569)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleInput(CorbaMessageMediatorImpl.java:951)
     at com.sun.corba.ee.impl.protocol.giopmsgheaders.RequestMessage_1_2.callback(RequestMessage_1_2.java:181)
     at com.sun.corba.ee.impl.protocol.CorbaMessageMediatorImpl.handleRequest(CorbaMessageMediatorImpl.java:721)
     at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.dispatch(SocketOrChannelConnectionImpl.java:469)
     at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.doWork(SocketOrChannelConnectionImpl.java:1258)
     at com.sun.corba.ee.impl.orbutil.threadpool.ThreadPoolImpl$WorkerThread.run(ThreadPoolImpl.java:409)

NestedException: java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : org.gjt.mm.mysql.jdbc2.optional.MysqlDataSourcePlease check that you have the driver in appserver's class path.

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Current Code
Session Bean C
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Required:
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Not Supported
     findByPrimary and getOrder methods

"The entity bean has a "void setOrder(Order param)" function that writes the Order to a database"
This functionality should be performed in the ejbStore method().
"a "Order getOrder()" function that clones and returns the internal Order object."
Sounds reasonable, except for the cloning part.
"The "ejbLoad()" function reads the Order object from the database"
Cool.
""ejbStore()" function is not implemented."
Whoops. Looks like your setOrder method is doing too much. It should do the inverse of getOrder (namely, setting the interal Order object), nothing more. Defer the persistence code to the ejbStore method.
"According to the SilverStream manual it does not maintain a pool of idle/unused entity beans, instead it instantiates beans as requested."
Manual? What's that? Assuming that is correct, better hope you don't ever get a high load. You might wanna look into JBoss.
"2) We sometimes get a TransactionRequired exception thrown when we have concurrent updates to two different objects of the entity bean."
How can you have concurrent access to two different objects?? Concurrency is inherently applicable to only one object.
In summary:
Write your beans properly, ejbLoad populates the bean with data, ejbStore persists the bean's data.
Get a better (and possibly free) appserver.

Cmp Entity Beans and collections

I am doing a proof of concept application and I have implemented an Entity bean which accesses through a DAO object to my Informix database and returns records based on a serial field called sightID. This works fine and I can access the records and store new records. I now need to demonstrate the power of CMP beans and return a collection showing all records for a particular field called Type. Here is where my problems start. If I am using CMP I need to map the primary key field to the primary key field of the database (this is sightID) the field I need to get the collection on is not a key field and is only a text field with one of four values. How can I use CMP to return a collection based on a non priomary key field? is this possible? I am willing to post all my code but there is 14 pages.
any help greatly appreciated
Connie

EJBQL???..
SELECT object(o) from table_object 0 where non_primarykey = 'value i want'
sanjay.

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...

Caching CMP Entity Beans with 9.0.2

Hi,
my CMP Entity Bean is accessed from a JSP-Page through a Stateless Session Bean. The Session-Bean executes findAll() on the Entity-Bean and the JSP-Page iterates over the Collection and displays the Fields through their getter-Methods. It turns out that every getXXX Methods results in a complete load of the Bean from the Database, so for 3 database-records with 4 attributes i get 12 SELECT - statements and 12 Activate/Load/Passivate cycles of the Entity Bean!!!!
I tried to setup the attributes in orion-ejb-jar.xml correctly, but that didn't show a difference:
-) exclusive-write-access="true" does only work in "read-only" mode (see oc4j_ejb_guide_r2.pdf)
-) setting timeouts didnt work
My Entity Bean settings are:
exclusive-write-access="true"
instance-cache-timeout="60"
max-instances="100"
max-tx-retries="0"
pool-cache-timeout="100"
The EJB-Callbacks are:
first the Session-Bean is created, and findAll() is executed - then all Entity-Beans are passivated again:
TestManBean Constructor called 1
TestManBean.setSessionContext() 1
TestManBean.ejbCreate() 1
PersonBean Constructor called 1
PersonBean.setEntityContext() 1
PersonBean.ejbActivate() 1
PersonBean.ejbLoad() 1
PersonBean Constructor called 2
PersonBean.setEntityContext() 2
PersonBean.ejbActivate() 2
PersonBean.ejbLoad() 2
PersonBean Constructor called 3
PersonBean.setEntityContext() 3
PersonBean.ejbActivate() 3
PersonBean.ejbLoad() 3
PersonBean.ejbPassivate() 1
PersonBean.ejbPassivate() 2
PersonBean.ejbPassivate() 3
now for every getXXX-Methods the following occurs:
PersonBean.ejbActivate() 3
PersonBean.ejbLoad() 3
PersonBean.ejbPassivate() 3
I user OC4J 9.0.2 Production with Oracle 8.1.6.
How can I turn on Entity-Bean Caching?
Thanks,
Gilbert

Hi Gilbert,
Someone recently asked a similar question to yours. Perhaps that thread will
be helpful to you?
Author: Valeri Kireitchik
Subject: how to set exclusive-write-access="true"
Date: May 17, 2002 10:18 PT
URL:
Re: Get the Table name by providing the Sequence name
The same person (Valeri) also asked his question on two other forums:
http://www.elephantwalker.com/rfa?id=549
http://www.mail-archive.com/orion-interest%40orionserver.com/msg19037.html
Good Luck,
Avi.

Entity Beans not getting garbage collected

Hi,
I am developing an application that is using EJBs utilizing several common design patterns (i.e. Session Facade, DAO, and Fast Lane Reader). All of the patterns used have come from books by Sun Microsystems Press.
As I have understood the pattern, the Session Facade pattern uses Stateless Session Beans (SLSB) to implement a desired functionality and accesses the entity beans locally. The results from the entity beans are placed into Value Objects and passed back to the client separating any direct access with the entity beans from the client. In my case, I am using BMP for my entity beans.
The problem I am seeing with Optimizeit is that none of my entity beans are getting garbage collected despite no references to them. The SLSB creates what entities it needs to perform a task at the local level, puts the data into a value object and goes out of scope.
Shouldn't the entity beans get removed if the object that references them has gone away or am I missing something?
Is there a proper way to set an entity bean (or any EJB for that matter) for garbage collection.
thanks in advance for any help...

You might even discover that entity beans can get created even before you use them.
Your application server creates "pools" of bean instances that it can use when it needs to. It is part of this role, and is done in order to optimize performances.
You cannot force them to be garbage collected. Even if you stop referencing them, the app server will.
When your create references to a bean, it (usually) won't create an instance. It will take an existing one, and load data into it, using ejbCreate or ejbActivate.
Hope this helps.
/Stephane

Very Basic Question about Entity Beans !!! Need your help.

Hi,
I have the following requirement:-
==============================
There is an application A, whose multiple instances can run
at the same time. There is some data/variable which is to be
globally shared (i.e by all the instances). I have thought of using
Entity Beans and putting that data in a single record in DB.
Approach A:-
~~~~~~~~~~~
Instance 1 of A (with Entity Bean ) -
-> Database (only 1 row exist)
Instance 2 of A (with Entity Bean ) -
Approach B:-
~~~~~~~~~~~
Instance 1 of A
-> Entity Bean -> Database (only 1 row exist)
Instance 2 of A
My Query is:-
1) In Approach A, both the instances of Application
have their own Entity Bean (running in same JVM as them,
packaged with Application)..Now both the entity bean instances
represent 1 row on Database...At one time only 1 Entity bean
will be performing the operation (read/write, other will be
disallowed).
2) In Approach B, both the instances of application(or Client) using
the same Entity Bean - which is representing 1 row of Database
Which is correct....I have read somewhere instance of Entity Bean
corresponds to 1 row of database....If that is the case, Approach
A would be wrong..
Please help.

1 Entity bean for 1 row is not true. An entity bean can represent data from multiple tables also. The correct statement is 1Entitybean for 1 resultset.
So in case 1, u have 2 instances of Application running so it should not be an issue.

Entity Bean Database Access Problem

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