Entity bean for shared acces without database access

Hi all,
I would like to create an entity bean to store data common for all application users. This bean does not have to have a database link, it should only keep data in memory until no user left.
Is it possible ? And if yes, how ?
I have already created a session bean that works but only keep data for one users session, and I have created an entity bean but it seems that it requires a database link.
Thanks
Sylvain

Sylvain,
I am assuming that you are using webdynpro for this.
You have a provision to use 'Dictionary' objects to handle CRUD operations in webdynpro and also at EJB level.
I can suggest you to handle this scenario in two ways.
1) If you are trying to perform the persistance at Webdynpro level, You can create the dictionary object straightaway in the webdynpro component.
2) If you are trying to perform persistance at EJB level using entity bean, I suggest you to maintain/create a dictionary object using your NWDS and access that Dictionary object at your entity bean using dictionary by packagename. Ofcourse you may have to write the CRUD operations code by urself.
I hope that this information would be most useful.

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SOS problem using one Entity bean for editing records. please help me

Hello
I have one great problem using one entity bean 2.1 and i am working with this problem several days and i dont solve it.
i am using this jb 2.1 for add new records to one oracle database and for editing records.
I have one great problem for editing records
I have one objets that is as one of my database table. (PersonaObj.java)
     //personaObj.java
     public class PersonaObj implements Serializable{
          private Integer id_persona; //this ishte database table autonumeric
          private java.lang.String nombre;
          now the set/get methods.
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     From one session bean i call the entity bena passing the objet
     into the entity bean (interface) i have one methods:
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          obj.setId_persona(getId_persona());
          obj.setNombre(getNombre());
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          setId_persona(obj.getId_persona());
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But i have one graet problem.
adding new record to the database i runs well but if i want to edit one recor appears this error:
=> Error <=
java.rmi.RemoteException: EJB Exception: ; nested exception is: javax.ejb.EJBException: EJB Exception: : java.lang.IllegalStateException:[EJB:010144]The setXXX method for a primary key field may only be called during ejbCreate.
at PersonasEJB_a43o8n__WebLogic_CMP_RDBMS.setId_persona(PersonasEntityEJB_a43o8n__WebLogic_CMP_RDBMS.java:328)
at PersonasEntityBean.setPersona(PersonasEntityBean.java:114)
at PersonasEntityEJB_a43o8n_ELOImpl.setPersona(PersonasEntityEJB_a43o8n_ELOImpl.java:45)
at PersonasSessionBean.editarPersona(PersonasSessionBean.java:849)
at PersonasSessionBean_bszo9t_EOImpl.editarPersona(PersonasSessionBean_bszo9t_EOImpl.java:208)
at PersonasSessionBean_bszo9t_EOImpl_WLSkel.invoke(Unknown Source)
into the session bean i make this (the session recibes one PersonaObj obj):
T56aContactosEntityLocal personaLocal ;
               try {
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                    objTmp.setEstado_a04("false");
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Please can you help me to solve this problem?

Hello Werner,
The mappings seem to be alright at a first glance.
Have you tried out un- and redeploying your application? Sometimes values appear to be cached in the server. So if you have deployed the application before you entered DB_BANK as alias this might solve the problem...
BR
Daniel

Entity bean for more than one table

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Yes, probably either using BMP entity beans, or creating a database view of the two tables.
However, the actual implementation depends a lot on your database and EJB container. Since I didn't see any details of these in your post, I suggest you research the documentation for both your EJB container and database.
[Of-course, I'm assuming that you are already using a database and EJB container :-]
Are you familiar with the following Web sites:
http://java.sun.com/j2ee/tutorial/1_3-fcs/
http://www.theserverside.com
Have you read the specification?
http://java.sun.com/j2ee/download.html
Hope this helps.
Good Luck,
Avi.

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Hi,
I am not able to create Entity and View objects for tables in TimesTen database using ADF. I have installed TimesTen client on my machine.
I have created a database connection by using connection type as "Generic JDBC" and giving driver class and JDBC URL. I am attaching screen shot of the same.
I am right clicking on Model project and selecting New option after that I am selecting ADF Business components and in it I am selecting Business components from tables and there I am querying for tables.I am getting list of tables and when I am trying to create a Entity object from the table after clicking finish Jdev is closing by itself giving an error.
Can anyone please help me how to create Entity objects for tables using TimesTen as database.I might be missing some jars or the way I am creating connection might be wrong or any plugins required to connect to TimesTen.

What is the actual error being given by Jdev? Are you sure that the JDBC connection is using the TimesTen JDBC driver JAR and not some other JDBC driver or the Generic JDBC/ODBC bridge?
Is ADF even supported with TimesTen?
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JDBC or Entity Beans for Read-Only Data?

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One query pulls about 700 rows from 6 different tables taking up to 20 seconds. The same call using JDBC takes 2 seconds. What is the proper thing to do?

One query pulls about 700 rows from 6 different
tables taking up to 20 seconds. The same call using
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EJB3.0 simple entity bean for customer example...

Can anyone provide a simple step by step instruction on how to start my application of a customer entity bean. like i could add / delete an entry to mySQL DB, i will use Sun as my appserver. im a newbie to ejb. i want to start with that CUSTOMER bean can anybody help pls ? thx! tata-yang

hello batzee i already have my appserver running
and found out that he place my EJBSample under Enterprise Application.
and with these modules inside:
-EJBsampleSun-ejb.jar EJBModule
-EJBsampleSun-war.war WebModule
my appserver has:
EJBsampleSun true ${com.sun.aas.instanceRoot}/applications/j2ee-apps/EJBsampleSun Redeploy
inside my application:
1. ejbsamplesun-ejb/src/conf/persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="EJBsampleSun-ejbPU" transaction-type="JTA">
<provider>oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider</provider>
<jta-data-source>jdbc/mySample_dbo</jta-data-source> //question: i have db in mysql named mySample_dbo with customer as my table did i declare it right?
<properties>
</properties>
</persistence-unit>
</persistence>
================
2. ejbsamplesun-ejb/src/java/ph/icomm/customer.class
package myejb.ph;
import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.*;
@Entity
@Table(name="Customer")
public class Customer implements Serializable {
private int id;
private String name;
private String email;
private String phone;
@Id
@Column(name="ID")
public int getId() {
return id;
public void setId(int pk) {
id = pk;
@Column(name="Name")
public String getName() {
return name;
public void setName(String n) {
name = n;
@Column(name="Email")
public String getEmail() {
return email;
public void setEmail(String e) {
email = e;
@Column(name="Phone")
public String getPhone() {
return phone;
public void setPhone(String p) {
name = p;
================
3. ejbsamplesun-war/src/java/web/postcustomer.class
// and here is my servlet
//simply trying to fetch the data in my customer table with ID = 11
package web;
import java.io.*;
import java.net.*;
import javax.servlet.*;
import javax.servlet.http.*;
import ph.icomm.Customer;
import web.PostCustomer;
public class PostCustomer extends HttpServlet {
/** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
* @param request servlet request
* @param response servlet response
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
/* TODO output your page here*/
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet PostCustomer</title>");
out.println("</head>");
out.println("<body>");
try {
Customer pCustomer = new Customer();
pCustomer.setId(new Integer("11"));
out.println("Customer Name is"+pCustomer.getName());
out.println("<br>");
out.println("Customer Id is:"+pCustomer.getId());
out.println("<br>");
out.println("Customer Email is:"+pCustomer.getEmail());
out.println("<br>");
out.println("Customer Phone is:"+pCustomer.getPhone());
} catch(Exception e) {
System.out.println("I am inside Exception");
out.println("<h1>Servlet PostCustomer at " + request.getContextPath() + "</h1>");
out.println("</body>");
out.println("</html>");
out.close();
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/** Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
/** Handles the HTTP <code>POST</code> method.
* @param request servlet request
* @param response servlet response
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
/** Returns a short description of the servlet.
public String getServletInfo() {
return "Short description";
// </editor-fold>
Now, is this complete ejb3.0 already? coz if ill try to RUN this project it give this error:
Deploying application in domain failed; Deployment Error -- null
C:\Inetpub\wwwroot\myfolder\_Project\EJBsampleSun\EJBsampleSun-ejb\nbproject\build-impl.xml:312: Deployment error:
The module has not been deployed.
See the server log for details.
BUILD FAILED (total time: 1 second)
This is quite a long post but have to make sure ill get your kind help and assistance. Thanks!
tata-yang

Mapping refresh without database access

Hello. I asked this before about 10 months ago (and the answer was in the
negative back then), but am wondering if there's been any change...
Is it now possible to run mappingtool refresh without it trying to access
the database? i.e. Without the need to specify the following Connection
parameters:
javax.jdo.option.ConnectionUserName: xxx
javax.jdo.option.ConnectionPassword: xxx
javax.jdo.option.ConnectionURL: jdbc:oracle:thin:@xyz:1521:ABC
I just want to update/create the (file based) mappings without connecting to
a database.
..droo.

No, it is not possible.

Deploying EJB 3.0 entity beans without a Datasource

[Cross-posted from the TopLink list]
My question: Is there any way to configure the container or persistence provider to defer trying to connect to the Datasource until I make some call that involves persistence? Or any other way to deploy an app containing entity beans without having a database configured?
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However in my prototype of the application, when I try to deploy to OC4J 10.1.3, as soon as the entity beans are detected the TopLink persistence provider tries to establish a connection to the db via either the configured or default DataSource. So if the db is unavailable, deployment fails. Since this is occuring at deployment, it happens regardless of whether I am actually using any persistence features or not.

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Concurrent entity beans access

I have failed to come up with a workable solution for concurrent entity bean access on the SUN reference implementation together with cloudscape.
I have created a test case and a webpage which describes my problem. If anyone can come up with a working solution (must work on the RI) I would be very thankful.
Please have a look at
http://www.offermanns.de/~rolf/ejb-concurrency/
and tell me what you think.
-Rolf

Hi,
I thought that this is a problem. But this isn't just
about this pattern. It is a general question about how
to get concurrent access to entity beans to work on
the RI.Entity Beans are the shared components , same instance is being shared between all the concurrent users so if the same component is a part of the longer transaction then the component can lead to the data corruption and to avoid that you have to set the ISOLATION Level for the concurrent running long transactions.Remember the Entity beans are shared components and are shared between all the cliens not like the Sessoin BEans where different clients can get different instances.
I tried to alter the cloudscape setting to SERIAZABLE,
but that won't help. (from the cloudscape log, it
seems, that the container switches back to READ_COMMIT
before every transaction.You dont have to change the setting in the Cloudscape,you require add the Isolation-level tag in the deployment descriptor.These can take the values as
1)READ_COMMITED
2)READ_UNCOMMITTED
3)REPEATABLE_READ
4)SERIALIZABLEI hope this will help.
Regards
Vicky

Entity bean (ejb 3.0) refactoring problem

I didn't find a better method than regenerating an entity bean after modifying the table definition and renaming the class after deleting the old one.
I'm not sure i can delete the old class representing the entity bean before regenerating it without any effects into the others entity beans.
It work fine but still a little problem. The refactoring process didn't change the name of the entity bean into the select clauses into queynamed injection.

I am facing a similar problem. Does JDeveloper 10g (10.1.3.3.0) provide an automatic process to update an Entity Bean definition when the underlying database table definition changes?
I also noticed that for JDeveloper to create all the relationships (i.e. @OneToMany, @ManyToOne) between multiple Entity beans, I need to create all the Entity beans together in one pass using the wizard. If two entities depend on each other, and not created together, JDeveloper will not create the relationships between them. Is there a way around that?
Thank you

Global Variable in entity beans

Dear Friends,
For example let us think that we have an entity bean for Customer.
and we created an instance of that bean for customer A and then for customer B.
So will the global variables in Customer bean be shared across Customer A and Customer B or will there be seperate instances for both Customers.
Thanking You,
Chamal.

Your concepts seem to be a little messed up.
For entity bean, remember the following:
1. each object/instance of entity bean represents a record in a database
2. when a client looks up an entity bean (typcially by using findByPrimaryKey method on home object), the record from database is searched and its values are stored in Entity Beans variables (this is probably what you mean by Global Variable. But thats an incorrect terminology in Java/J2EE. Class attribute is the correct word)
3. In step 2, you fetched a record and that record is represented by a java object, which is nothing but entity bean.
4. Now if you make changes to this java object, these changes will persist in the database. That is the essence of entity bean.
5. If you use the home object's findByPrimaryKey method and look for the same record, no new object will be created. The 2 remote objects will point to the same entity bean on the server.
6. If yo use the home object's findByPrimaryKey method and look for another record/customer, a new object will be created on the server. This new entity bean will map to the new record.
Note taht the attribtues of CustomerA and customerB will never be shared.
hope that helps

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.

Can anyone explain the advantage of entity beans

Hi All,
I was wondering if anyone can explain the advantage of entity beans versus session beans. We argue that session beans can perform retrival/storage more efficiently than having an extra layer of entity beans. Basically we can't see any advantage entity beans have to offer except caching a row in a database table. I'd like to see the other side of the argument. So please if someone is an expert in this field, please advise us.
Thanks in advance for any argument
Regards,
Di

-Caching the data is one.
-Seperation of logical layer. Entity beans are used to represent the data layer, while session beans hold the business rules. This is some what nebulous as some business rules are often best implement directly in the database, although they might be replicated at a different level as well.
-Mapping a logical layout to a physical layout. For example 'customer' might have a 'fax' and 'voice' line which is represented as a Customer class with two TN classes hanging off of it. The database might represent this in one of two ways: two tables (customer and TN) or one table (customer with two tn fields).
Both of the above are more readily apparent when dealing with distributed data. If one database holds the customer and another holds the TNs, then caching of data is more relevant and dealing with the actual CRUD stuff is much more complicated. This is likely to lead to a session bean offloading the logic to another class anyways - and it becomes a defacto bean.
And a really excellent example is when the entity bean represents data that isn't accessed via normal database calls. For example the customer record might be on a legacy system which can only be accessed via screen scrapping and batch input. That single customer entity is now the front end for a large sub-system.
All such answers are usually pretty wishy-washy anyways. Why should one use java over C++? Most decisions of this nature are made because developers want to use something rather than because there is any strong technical reason to do so. And even though keeping the data layer seperate for the rules layer seems like a good idea, compromises are always required and adding layers adds complexity.

BC4J DAOs vs. Local Entity Beans

We are beginning a brand new project and trying to evaluate the costs/benefits of using BC4J entity objects versus local entity beans for our persistence needs.
I've read the "Simplifying J2EE and EJB Development with BC4J" white paper including the "How Does EJB 2.0 Change the Picture?" section, but that seems to have been written at a time when EJB 2.0 support was a rarity.
I'd like to get some feedback from people who have had experience with both. We are basically starting this application from scratch, although we have relational tables from our legacy C++ application that will serve as the basis for the Java object model. So what would we gain/lose by using entity objects?
I must admit, I'm leaning toward using entity beans over a vendor-specific persistence framework, but if there are compelling reasons to choose entity objects (besides those mentioned in the white paper), I'd like to hear them. Please speak slowly, as I'm new to BC4J. :)
Thanks for your time.

I've read the "Simplifying J2EE and EJB Development with BC4J" white paper including the "How Does EJB 2.0 Change the Picture?" section, but that seems to have been written at a time when EJB 2.0 support was a rarity.IMO there's no change.
What Sun doesn't tell you in the specs, but is much talked about on theserverside.com and in most
anti-patterns threads, and in the up coming book J2EE Anti-Patterns; EJB Entities are basically
broke with no solution. Reason: EjbStore() can throw an exception due to DB constraint violation
after the business method returns. This drives the scenario where all business integrity is
forced up into the middle tiers (EJB and business mediator tiers). etc etc ... EJB Entities are
useful for the 5% to 1% of a business model and application that is transactional IMO.
I.E. 95%++ of most apps/web sites are read only. Why use a heavy and expensive transactional
component for reading rows from a DB to be displayed on an Inventory screen? The only reason
to do this is if you have stock in Sun and your appserver vendor or want your project to last
forever or get canceled. -- Seriously, do your home work, using Entities as your persistance
tier mediator, for the 95% of your project that's read only, and for reports which involve
joins, select criteria etc etc will be a serious problem to just code and even bigger problem
to be responsive and scalable.
Do this experiment: implement a report that joins several tables, selects on where criteria,
orders by some attribute in EJB Entity bean technology. Seriously try to code this solution.
Hint: spray water on your appserver box since it'll almost explode. :)
Then try: do the same report in SQL. One SQL statement usually will do it and it's all in the
DB. The data returned to the middle tier is ready for JSP formating.
Try another EJB experiment: implement a finder based on criteria that returns a Collection.
Do the same in SQL: time the perf difference.
Hint: Maybe you're getting the picture, that EJB Entity 2.0 --> 10.0 what-ever, never wrote into
the specs any means for joins, or high perf finders based on criteria.
My opinion and experience: EJB Entity is good for one portion of a project if that; the single
part that's transactional (usually the shopping cart or similar). All other data access needs
to be through a DAO tier that's SQL based. With BC4J you get transactional support too, so
why bother with EJB, except to be wrapped by SLSB's for remotability from the client.
I'd like to get some feedback from people who have had experience with both. We are basically starting this application from scratch, although we have relational tables from our legacy C++ application that will serve as the basis for the Java object model. So what would we gain/lose by using entity objects? I'm at the end of phase one of a medium scale BC4J project which was initiated after scrapping
a Sun Blueprint J2EE 1.2 architecture for the above reasons, plus the unmentioned time to market
issue. We found hand coding the Sun architecture to be 400% slower, if you don't hit any of the
above mentioned bumps in the road. We never got to reports, which would have been imposible without
custom DAOs.
I must admit, I'm leaning toward using entity beans over a vendor-specific persistence framework, but if there are compelling reasons to choose entity objects (besides those mentioned in the white paper), I'd like to hear them. Please speak slowly, as I'm new to BC4J. :)You're not the first to ask this question nor the last. Sun's happy talk in the face of their
king has great cloths sell job to fend off .net will take more than just J2EE Anti-patterns books
to displell. Try the reports and finders experiements in EJB 2.0. You'll no doubt learn alot
and read more news group posts in the process.
Heck, you might even discover that 903 oc4j's CMR and EQL can instantiate 1000's of Entity beans,
JNDI entries, return a Collection of handles, your client get the ValueObjects and build a report
in less than a minute and 100's of customers can do this simultanteously. __NOT__ :)
Cheers,
curt

Entity bean for shared acces without database access

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