Object Oriented Databases and entity beans?

Does one of the authors care to comment on the benefits of using OODBMS models versus RDBMS models for entity beans? Any differences between BMP and CMP in this scenario?
Thanks!
Peter

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Object Oriented Databases

Has anyone had any experience with connecting Forte with an Object Oriented
Database (such as ObjectStore)?
Two things:
1. Impact on application architecture
2. Speed of database operations.
Thanks
Dan Parker
Michelin North America (Canada) Inc
902 753 1789
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Is oracle OODBMS (Object Oriented database management system)?

Hello, All
Is oracle OODBMS (Object Oriented database management system)? and if yes, please explain.
I have query in my mind so, I just posted here.
Regards,
Rahul
Edited by: Rahul K. Thakar on Nov 3, 2010 12:03 PM
Edited by: Rahul K. Thakar on Nov 3, 2010 12:04 PM

I believe the precise answer is that Oracle is ORDBMS (Object-Relational DBMS).For a brief period in time Oracle Corporation offered a product called Object Oriented Oracle (OOO).
It was such a wonderous product that it was buried in the trash can of history when it did neither task very well.

Only oracle object tables to create object oriented database

Can we use only oracle object tables for a database and if it can be done, can we create pure object oriented database with oracle. How it can be done?
help..
thank you..

PriyashanthaHP wrote:
I have no my own definitions for OODB. There are lot in the internet. I'm asking, can't we use that OODB concept with oracle. And gave you an example with 'employee' and 'department' tables. I asked that can we create object tables for these two tables keeping their relationship
thank you..
There is no way to answer that without knowing what YOU mean by OODB.
See the database concepts doc
http://docs.oracle.com/cd/B28359_01/server.111/b28318/schema.htm
Nested Tables
You can create a table with a column whose datatype is another table. That is, tables can be nested within other tables as values in a column. The Oracle database server stores nested table data out of line from the rows of the parent table, using a store table that is associated with the nested table column. The parent row contains a unique set identifier value associated with a nested table instance.
Oracle Database Object-Relational Developer's Guidefor further information on nested tables
Oracle Database Advanced Application Developer's Guide

JSF and entity beans

I'm trying to create an application using JSF for the presentation layer and entity beans and stateless session beans in the model layer using CMP, for deployment with JBoss. I'm basically stuck though on the communication between the backing bean and the session bean (where do I define the JNDI names, the database connection etc). Can anybody suggest a good tutorial/example showing JSF with EJBs?

Well I was interested in the same topic, I once thought `Sun Java Studio Creator EA2` will have an easier approach ... well it dun seems easy to me neither.
Anyone of you tried acheiving the purpose by using that approach b4?
I'm currently working on a `JSF-based portlet` project with `entity beans + managed beans` ... well its very much source shared ... but I'm still green :P
Anywhere, I'm starting a new thread called `JSF Portlet developement` in my blog (`http://avatar21.superihost.com`), feel free to comment(any ideas will be mostly appreciate).
Regards,
Avatar
there is no specific support in JSF for EJBs.
the definition of connection pools and other JNDI
resources are subject to the servlet spec which JSF
is built on top of.
you can find usefull examples in the sun J2EE
tutorial.

Flow of sessiob bean and entity bean

Hi All,
Can any one help me how is the flow of session and entity beans i.e
What method is called first and what method is called next.
There are so many methods like create(),ejbcreate(),
ejbActivate(),ejbPassivate(),ejbDelete() etc.
What is the flow of these methods and when they are called.

Hi vasudulla,
If you can, go to the bookstore and look for the book:
Entreprise JavaBeans 3rd Edition by Richard Monson-Haefel.
In the Appendix B, you can see the State and Sequence Diagrams, all the things you want to know about the Flow.
--Paul.

How many ejbCreate() can be in Session and Entity Bean???

Hi,
How many ejbCreate() method can be in a Session and Entity
Bean???
How many can be in Stateless and Stateful SessionBean???
How many can be in CMP and BMP SessionBean???
Thanks,
JavaCrazyLover

How many ejbCreate() method can be in a Session
ion and Entity
Bean???For Stateful Session Beans and Entity Beans, as many as you'd like.
Stateless Session beans can only have one, since their ejbCreate methods can not take any parameters.
>
>
How many can be in CMP and BMP SessionBean???If you mean CMT/BMT(Container-Managed transactions / Bean-Managed Transactions), then
the answer is the same. The create method requirements are independent of the transactional nature of the bean.
If you really mean CMP/BMP(Container-Managed Persistence / Bean-Managed Persistence) , it doesn't apply to session beans, only entity beans. However, even for entity beans, CMP vs. BMP has no bearing on the rules regarding # of create methods.
--ken
>
>
Thanks,
JavaCrazyLover

Object Oriented Analysis And Design

Hi,
Can somebody suggest how to satrt the Object Oriented Analysis And Design. Is there any suitable site for this?
Thanks,
Subodh.
SCJP 1.4, SCWCD 1.4, SCBCD 1.3.

Many thanks Leelavati for your response.
chariflakchiri , I think you interpreted in a different way.Can you visit
http://www.objectdiscovery.com/programming/java/ooad/outline.html.
Then you will come to know what is required for you to say that you know OOAD. See what percentage of the tutorial you really need to get SCJP, SCWCD, SCBCD.

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.

Why generate object-oriented database schema

Let me begin with an example:
public class Base
protected int id = 0;
protected String name = null;
public class Derived extends Base
protected int type = 0;
Derived class and Base class form an object-oriented inheritence. After
using SchemaToolTask, the following table definition is generated :
create table base
id INT NOT NULL,
name VARCHAR(255),
PRIMARY KEY (id)
create table derived
id INT NOT NULL,
type INT,
PRIMARY KEY (id)
Actually, RDBMS is ER-oriented. Every meaningful entity corresponds to a
database table. But in this example, maybe "Base" has no any meaning, just
for abstraction. So why we must generate this table ? Why cannot be
configurated to just generate
create table derived
id INT NOT NULL,
name VARCHAR(255),
type INT,
PRIMARY KEY (id)
This will not only avoid join operation in SELECT, but also reduce the table
size according to Base class.
Thanks
Liang Zhilong
EMail : [email protected]
Tel : (021)54235858-6650
Fax : (021)54235800
PhotonicBridges Co., Ltd.
12F, 900 Yi Shan Rd., Shanghai 200233

As I said, this is quite high on our project plans.
On Wed, 25 Jun 2003 14:41:29 +0800, Liang Zhilong wrote:
I believe your concern is reasonable. However, in our application, the
operation you assumed( to find all base instances owned by class C) is
rare, so it'll be useful if my suggested mapping is taken as an option.
Moreover, we should not get better performance at the cost of worse
database schema. Kodo should have enough capacity to optimize database
operations. For example, to find all base instances owned by class C, kodo
should issue a "SELECT col1, col2 FROM a UNION SELECT col1, col2 FROM b".
"Stephen kim" <[email protected]>
??????:[email protected]...
This sort of mapping is on our project plan but know that there a number
of severe performance penalties that can happen with the mapping you
describe. If you desire to lack the join, a flat-class mapping is the
most efficient table structure.
Take for example the multiple classes problem:
base
|_ A
|_ B
which would result in table a and table b. Now try to do an ordering
query. You would issue 2 selects and then have to merge in memory. To
do any relation join, again you multiply the number of SQL statements by
the number of subclasses (e.g. to find all base instances owned by class
C, you would have to query against a and b).
On Wed, 25 Jun 2003 12:39:39 +0800, Liang Zhilong wrote:
Let me begin with an example:
public class Base
protected int id = 0;
protected String name = null;
public class Derived extends Base
protected int type = 0;
Derived class and Base class form an object-oriented inheritence.
After using SchemaToolTask, the following table definition is
generated :
create
table base
id INT NOT NULL,
name VARCHAR(255),
PRIMARY KEY (id)
create table derived
id INT NOT NULL,
type INT,
PRIMARY KEY (id)
Actually, RDBMS is ER-oriented. Every meaningful entity corresponds to
a database table. But in this example, maybe "Base" has no any
meaning,just
for abstraction. So why we must generate this table ? Why cannot be
configurated to just generate
create table derived
id INT NOT NULL,
name VARCHAR(255),
type INT,
PRIMARY KEY (id)
This will not only avoid join operation in SELECT, but also reduce the
table size according to Base class.
Thanks
Liang Zhilong
EMail : [email protected]
Tel : (021)54235858-6650
Fax : (021)54235800
PhotonicBridges Co., Ltd.
12F, 900 Yi Shan Rd., Shanghai 200233--
Steve Kim
[email protected]
SolarMetric Inc.
http://www.solarmetric.com
Steve Kim
[email protected]
SolarMetric Inc.
http://www.solarmetric.com

Basic difference between stateful and entity beans???

Could anyone please explain the basic diff between stateful bean and an entity bean.as per my understanding,stateful beans are extensions to clients.they perform a job of a client and they r not persistent.also their state goes off when the server crashes or the machine is reeboted.while in contrast,an entity bean can retain its session coz' they represent a persistent field in the DB.What i have seen in few books(O'reilly,etc)where a session bean can insert some values into the DB,which means it also represents a persistent object in the DB,which contradicts the statement that "stateful session beans dont represent any persistent object in the DB".Could anyone please elaborate on this.Thanks in advance.
Jameel

Thank u very much crackers for ur valuable
suggestions.I'll throw a different one in here for free: clarity of writing is a highly-valued and useful skill in a software professional. This is especially true these days when concepts need to be clearly explained to a variety of technical peoples from all over the world. And then there's the other side of the coin: Management.
You have to get your thoughts across in a very precise manner and, unfortunately for those who have to learn it as a second lanugage, English seems to be the overall preferred medium. Which makes it even more important to use "correct" English in written communications. If you don't, your credibility diminishes and you appear to be (horrors!) unprofessional It's not that much harder to type "you" than it is to use a single letter. Besides, most people that "pay by the byte" appreciate the clarity, as well (as I've seen on Usenet, by way of covering my ass).
Now, back to our regularly scheduled post...
Is this wat u were trying to say if i
understood u correctly.Yes, the EntityBean is directly related to the data being persisted: in this case, a database table. So, using your example from below, the DB table would have two fields: a VARCHAR 'Name' and an INT 'Age.' The EntityBean would have corresponding fields/properties/variables, String name and int age.
"WHICH BEAN (Entity
or Sateful Session) SHOULD I GO 4???"No easy answer. The best one is: it depends. On what? It depends upon what you're trying to do with the data, how it's presented/manipulated, load requirements, environmental requirements, caching strategies, and about another dozen or so other high-level requirements.
My personal preference is if I need caching and the number of EntityBeans actually in existence is pretty "low" (another nebulous and arbitrary value, depending), I'll use a StatelessSessionBean as a Facade (search for "patterns" here in the forum), with the persistence in CMP EntityBeans. Which is influenced by the fact that I like playing with CMP. ;D

8.1.7 and Entity Beans. Where is Patch 8.1.7.1???

I would like to be able to deploy CMP Entity Beans to 8.1.7 on Solaris using JDeveloper 3.2.2
The release notes indicate that this is a bug and is awaiting a patch. My two questions are:
1. When can we expect Patchset 8.1.7.1 for Solaris?
2. Could someone please describe for me the best way to write a CMP Entity Bean in JDeveloper 3.2.2 (w/descriptors & JAR'ed etc...) and then use the Oracle Command Line tools to load this bean? ie. what are the pitfalls?
Thanks in advance.

Thx alot..
When will JDev 3.2 be available for evaluation download ?
(The firm im working for is about to buy a complete system from the east, and i need to know how things perform before recommending purchase of system/archtecture and oracle tools).
Incedently, i experienced a problem with session beans on 8.1.6, if i killed my client app somewhere along a lookup and remote.create the sessionbean would completely die, only thing to do was to redeploy it(not even reboot cured it) (i could create it, but reading serilized objects gave a marshall exception every single time..)
I want to know if this is a known issue? and if it is, has it been 'fixed' in 8.1.7?
By the way, everything is running on localhost on a win2k pro box.
Thx alot for your time.

RemoteExceptions and Entity bean failover

The documentation gives an example of how to achieve failover with
          entity beans. (See below). How can one tell that the RemoteException
          is due to the server being down rather than some other reason.
          For example in EJB 1.0 aren't many exceptions generated in the bean
          wrapped in a RemoteException? For example if there is an SQLException
          the bean might throw a RemoteException that wraps the SQLException. In
          such a case it doesn't make sense to try it again.
          So what is the correct way to find out whether the exception is due to a
          server failure rather than some other reason?
          dan
          AccountHome home =
          (AccountHome)ctx.lookup("example.AccountHome");
          Account account;
          int attempts;
          while (attempts < LIMIT) {
          try {
          tx.begin();
          account = home.findByPrimaryKey(ACCOUNT);
          account.deposit(500);
          account.withdraw(10);
          tx.commit();
          break;
          catch (RemoteException re ) {
          // Retry
          try {
          tx.rollback();
          attempts++;
          catch (Exception e) {
          // Something unrecoverable has happened
          throw e;


Yes, this is the "nasty" case as I've heard several people put it. It's among the
          problems that make distributed programming difficult. Since the database is managing
          the transaction log, the other app servers in the cluster do not know if the tx was
          committed or not either.
          -- Rob
          dan benanav wrote:
          > If a remote exception is thrown from an entity bean then is it the case that we know
          > the transaction has rolled back? What if the server went down after the transaction
          > was committed?
          >
          > dan
          >
          > Rob Woollen wrote:
          >
          > > dan benanav wrote:
          > >
          > > > Isn't there a more definitive way to determine whether the problem is due to a
          > > > connection error or the server being down?
          > > >
          > >
          > > My first answer to your question is why do you need this? Both a db
          > > connection error and the server going down should be relatively rare events in a
          > > production system. RemoteException is meant to indicate that a system-level
          > > error has occured and the transaction has rolled back. Doing another find in
          > > this case is not going to limit your application's performance / scalability.
          > >
          > > -- Rob
          > >
          > > >
          > > > Rob Woollen wrote:
          > > >
          > > > > dan benanav wrote:
          > > > >
          > > > > > The documentation gives an example of how to achieve failover with
          > > > > > entity beans. (See below). How can one tell that the RemoteException
          > > > > > is due to the server being down rather than some other reason.
          > > > >
          > > > > Any application error should be thrown as an application exception that
          > > > > you could obviously distinguish from RemoteException.
          > > > >
          > > > > As you correctly point out, db errors like SQLException are often
          > > > > wrapped in RemoteException when they reach the client.
          > > > >
          > > > > I would code the application to give up if it gets an application
          > > > > exception. For instance, if you try to withdraw more money than you have,
          > > > > there is no sense in retrying.
          > > > >
          > > > > I would retry (up to a small limit) on RemoteExceptions if it makes
          > > > > sense in your application. Even SQLExceptions may be transient. For
          > > > > instance, Oracle may not have been able to serialize your transaction on
          > > > > the first attempt, but your second try might go through.
          > > > >
          > > > > -- Rob
          > > > >
          > > > > >
          > > > > >
          > > > > > For example in EJB 1.0 aren't many exceptions generated in the bean
          > > > > > wrapped in a RemoteException? For example if there is an SQLException
          > > > > > the bean might throw a RemoteException that wraps the SQLException. In
          > > > > > such a case it doesn't make sense to try it again.
          > > > > >
          > > > > > So what is the correct way to find out whether the exception is due to a
          > > > > > server failure rather than some other reason?
          > > > > >
          > > > > > dan
          > > > > >
          > > > > > AccountHome home =
          > > > > > (AccountHome)ctx.lookup("example.AccountHome");
          > > > > > Account account;
          > > > > > int attempts;
          > > > > >
          > > > > > while (attempts < LIMIT) {
          > > > > > try {
          > > > > > tx.begin();
          > > > > > account = home.findByPrimaryKey(ACCOUNT);
          > > > > > account.deposit(500);
          > > > > > account.withdraw(10);
          > > > > > tx.commit();
          > > > > > break;
          > > > > > }
          > > > > > catch (RemoteException re ) {
          > > > > > // Retry
          > > > > > try {
          > > > > > tx.rollback();
          > > > > > attempts++;
          > > > > > }
          > > > > > catch (Exception e) {
          > > > > > // Something unrecoverable has happened
          > > > > > throw e;
          > > > > > }
          > > > > > }

Is Berkeley an object-oriented database?

As the subject described, please help me to understand if the Berkeley is an object-oriented, or a data structure based database.

Hi Kevin,
A Berkeley DB database is like a relational table. Data is stored as key/data pairs and a key/data pair (a record) is similar to an RDBMS row with a primary key.
What Berkeley DB is not: http://www.oracle.com/technology/documentation/berkeley-db/db/ref/intro/dbisnot.html
What is Berkeley DB: http://www.oracle.com/technology/documentation/berkeley-db/db/ref/intro/dbis.html
Do you need Berkeley DB?: http://www.oracle.com/technology/documentation/berkeley-db/db/ref/intro/need.html
Bogdan Coman

Object Oriented Patterns and Visio

Visio question:
Does anyone know if there are established shapes for each (or any) of the object oriented patterns? If not, is anyone working on that or interested in that?
Since they all have names (Momento, Proxy, Iterator, Mediator, Observer, etc.) it seems like they ought to each have their own shape. Since Object Oriented is all about communication of intent, each pattern having its own recognizable shape would go a long way toward a more meaningful communication through diagram. Also, if they each had their own shape, then the super-patterns (based on commonly grouped patterns and interactions) could also be easily represented.
Blaine

I'm kind of making an assumption here and if it's in error then feel free to disregard the rest of this post.
Assumption that you're thinking terms of shapes for representing in UML the various patterns. Everything you need is right there in front of you already regardless of whether you use Visio, Rational, Poseidon or some other UML tool.
Patterns are not individual constructs. One does not make a Mediator class. One makes a Java class that is an implementation of the Mediator pattern. As such you would see in the static class diagram the same grouping of classes for an X Mediator as you would for Y Mediator. That is the image you're looking for. It's not a single widget that you drag onto the screen, it's in the pattern itself.
If, however, you're talking about something like a graphical representation to give to managers that says "Here be Momento patterns", then I would postulate that you're trying to communicate information that they don't need nor should they concern themselves with. Patterns are an implementation issue. They deal with, "How" we will solve a problem, not what problem will we solve. Mangaers, IMNSHO, need only concern themselves with what problems we will solve, not how they will be solved.
Just my 2 krupplenicks on the subject, your milage may of course vary.
PS.

Object Oriented Databases and entity beans?

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