Disadvantages of using entity beans.

can I know the disadvantages of using entity beans.

sigh I guess if someone puts it on a website it must be true...
"Forces the use of a heavy component mechanism for fine grained business objects."
Heaviness is not some arbitrary side-effect. It is directly due to the services provided by the EntityBeans (transactions, etc). If you need those services, you pay the price. If you don't then you shouldn't be using EJB to begin with. Also with the advent of LocalInterfaces, fine-grainedness is no longer a liability.
"More complex than JDO limiting developer productivity."
Perhaps it has less to do with limited productivity, and more to do with limited developers.
"More difficult to achieve good performance."
Compared to a simple data storage mechanism, sure.
"Inheritance not supported."
Really? Wow, I guess all the EJB code I've written for the last 3 years doesn't really work.
"Cannot be used for persistence in non-application server environments."
Uhh, yeah, but seeing as how the decision to use EJBs is not limited to the persistance scheme, the non-use of an application server is moot.
"There is no dynamic query mechanism to lookup entity beans (finders are specified at compile time)."
And what compiled business process (i.e SessionBeans) requires dynamic lookup of arbitrary data? Humans performing search functions can be done via entity beans, but probably should not be done since a large searches do not (or very rarely) need to be transactional.
"It is not easy to write unit tests for beans as it is not possible to use them outside of the application server."
For a long time this was true, but there are now many unit test suites designed for J2EE.
"No support for automatic primary key generation."
In the spec, no. But it's fairly trivial to implement on your own.
"Only relational databases are supported."
If you use CMP, yes. If you use BMP, you can do whatever you want inside your ejbLoad()/ejbStore() methods. Another reason to not use CMP.

Similar Messages

Insert data into table from JSP page using Entity Beans(EJB 3.0)

I want to insert data into a database table from JSP page using Entity Beans(EJB 3.0).
1. I have a table 'FRIENDS', (in Oracle 10g database).
2. It has two columns, 'NAME' and 'CITY'. Both have datatype strings(varchar2).
3. Now from a JSP page, having two textfields, 'NAME' and 'CITY', I want to insert data into table 'FRIENDS'.
4. In between JSP and database is a Entity Bean(EJB 3.0) and a stateless session bean.
5. I am using JDev as editor.
Please provide me code ASAP or link with similar example.
Thank you.
Anurag

Hi,
I am also trying that scenario. So u can
Post the jsp form data to a Servlet which will act as a Controller.
In the servlet invoke the business method.
Similar kind of app is in www.roseindia.net
Hope this would help u.
Meanwhile if u get any optimal solution, pls post it.
Thanks,
Happy Java Coding.

Data Warehouse report query using Entity Beans

I have used the EJB technology on one project, so I am not all that familiar with
best practices.
In my new project, I have to produce reports using a query that goes against a
dimensional database. I am wondering what options I have to run the query and
extract the results given that the application will run on WebLogic.
1) Straight JDBC
2) BMP
3) CMP (could be a problem because the quety is a join query, but I am not sure
if WebLogic requires that the query is against a table rather than a view)
The query is read-only. I am more interested in ease of coding and code management
rather than application performance at this point because I think the query will
spend a relatively large time executing on the Oracle database.
I would like to hear the best practices to be employed in this case. Thanks very
much!
Ravi.

Don't use entity beans for this. Straight JDBC is not perfect either, but it
is preferable to entity beans for this type of work.
Peace,
Cameron Purdy
Tangosol, Inc.
Clustering Weblogic? You're either using Coherence, or you should be!
Download a Tangosol Coherence eval today at http://www.tangosol.com/
"Ravi Navanee" <[email protected]> wrote in message
news:3c92693d$[email protected]..
>
I have used the EJB technology on one project, so I am not all thatfamiliar with
best practices.
In my new project, I have to produce reports using a query that goesagainst a
dimensional database. I am wondering what options I have to run the queryand
extract the results given that the application will run on WebLogic.
1) Straight JDBC
2) BMP
3) CMP (could be a problem because the quety is a join query, but I am notsure
if WebLogic requires that the query is against a table rather than a view)
The query is read-only. I am more interested in ease of coding and codemanagement
rather than application performance at this point because I think thequery will
spend a relatively large time executing on the Oracle database.
I would like to hear the best practices to be employed in this case.Thanks very
much!
Ravi.

Can anyone describe using entity beans for persitance in Software Architect

Can anyone describe using entity beans for persitance in Software Architecture you built for a product?

Although this forum is supposed to help you gain knowledge on entity beans, its not a free rider that's supposed regurgitate everyone's knowledge to you.
Read something first and then clarify your thoughts with this forum.

To use Entity Bean or Oracle stored Package?

Currently, in my project, Weblogic8.1 and Oracle is used, but lots of business logic is implemented using Oracle stored Packages, many of these packages have a package level readonly lookup table(like index-by table or nested table), which is populated with data from database, once the package is called, and is accessed very often in subsequent calls of stored procedures.
Since, in Weblogic server, a connection pool is maintained, and those package level lookup tables would be stored as session data in oracle PGA, I'm afraid this might cause oracle database server to be overloaded.
to fully take advantage of middleware cache service that weblogic provide, should I move those business logic out of oracle and implement them using like read only entity bean?
any help appreciated!

Its very hard to say without knowing the usage patterns of the data. It sounds like you have a lot of read-only entities. These could be spread around a WLS cluster, therefore there is more scalability and performance with this option. However, I would not neccessarily rewrite business logic from SP into EJB just for middle-tier caching.
If its a DB intensive app with lots of SQL, then if the calls are within SP's, there is only 1 call from WLS and the DBA ought o be able to tune the DB usin read-ahead and other DBA semantics. If there is locality of reference in the data, again, DB can use read-ahead better than WLS, although RO cache in middle is more scalable than DBMS.
I wouldnt rewrite business logic from SP to EJB/Entity beans to take advantage of cache, especially if there is no locality of read-only reference to data. Oracle could do this better in my opinion, especially if SP's already exist
Need for information on the usage patterns of the data - how is it CRUD'd.
I would use-case the steel threads and put them under test load to see if the SP's really are an issue, since this is an architecture decision. What state is the project at? Live/Dev? Inception?

Database access using Entity Beans

How does it work? In the examples I've seen, there is no SQL statement
being generated, and I no code establishing the JDBC bridge...
What am I missing? How do I look up a record in a database using an
entity bean?
Thanks!!!
-Dan

The Entity Bean remote interface methods access the database.
InitialContext ic=new InitialContext();
EntityBHome eh = (EntityBHome)ic.lookup("com.ejb.EntityBHome");
EntityB entityB=eh.findByPrimaryKey(primarykey pk);
[email protected] (Dan M) wrote:
How does it work? In the examples I've seen, there is no SQL statement
being generated, and I no code establishing the JDBC bridge...
What am I missing? How do I look up a record in a database using an
entity bean?
Thanks!!!
-Dan

Multiple Database Pooling using Entity Bean

Hi,
Can anyone come across this problem? I have an entity bean (BMP). I want to connect to multiple databases(Oracle, My-SQL, MS-SQL Server). The application is like this. if a request come from the client i have to identify the client request and connect to the database. How to do this. How to connect to get the pool from the connection pooling. Please reply its urgent.
thanks
Prem

Thanks for ur reply.
what the point is i want to identify the client request and send this request to that bean. i have developed 30 cmp beans, if i have to identify i have to change all cmp to bmp, is there any solution to this.

Getting Error while trying to create table using entity beans

This is the output on console.
javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean; neste
d exception is: javax.ejb.EJBException: nested exception is: java.sql.SQLExcepti
on: [Oracle][ODBC][Ora]ORA-00942: table or view does not exist
javax.ejb.EJBException: nested exception is: java.sql.SQLException: [Oracle][ODB
C][Ora]ORA-00942: table or view does not exist
java.sql.SQLException: [Oracle][ODBC][Ora]ORA-00942: table or view does not exis
t
at sun.jdbc.odbc.JdbcOdbc.createSQLException(JdbcOdbc.java:6879)
at sun.jdbc.odbc.JdbcOdbc.standardError(JdbcOdbc.java:7036)
at sun.jdbc.odbc.JdbcOdbc.SQLExecute(JdbcOdbc.java:3104)
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.execute(JdbcOdbcPreparedState
ment.java:214)
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.executeQuery(JdbcOdbcPrepared
Statement.java:89)
at com.sun.ejb.persistence.PersistenceManagerImpl.primaryKeyExists(Persi
stenceManagerImpl.java:289)
at com.sun.ejb.persistence.PartitionImpl.afterEjbCreate(PartitionImpl.ja
va:640)
at CallerBean_PM.ejbCreate(CallerBean_PM.java:96)

This is the output on console.
javax.ejb.TransactionRolledbackLocalException:
Exception thrown from bean; neste
d exception is: javax.ejb.EJBException: nested
exception is: java.sql.SQLExcepti
on: [Oracle][ODBC][Ora]ORA-00942: table or view does
not exist
javax.ejb.EJBException: nested exception is:Look at what the bolded text is telling you. This could be because:
1. The table/view actually does not exist in the oracle instance that you've connected to
2. OR, the user id that you used to connect to the db does not have the right permissions granted to it.

Error while using sybase trigger with the CMP entity bean,ejb version 2.1

Hi All,
I am using ejb version 2.1 and using entity bean (Transaction required) ,i am trying to update data in sybase(ver 12.3) database table
I am using session bean(Transaction required) to update the multiple entity beans in a while loop.It is working fine .But when i am trying to run it with the trigger which updates multiple tables in different sybase databases on update of each entity.Then it throws NoSuchEntityException and it rollback the whole transaction.
My trigger has only few simple update statements and the trigger runs fine without my CMP entity bean.is the CMP does not support the update triggers in sybase or is it the problem with the transaction.
Please help
Thanks
Anshu

If you can have a look at a cmp example in the samples that ship with the server. My guess is that the weblogic-ejb-jar.xml file is missing the <persistence-use> element which for 810 would look like:
<persistence>
<persistence-use>
<type-identifier>WebLogic_CMP_RDBMS</type-identifier>
<type-version>7.0</type-version>
<type-storage>META-INF/weblogic-cmp-rdbms-jar.xml</type-storage>
</persistence-use>
</persistence>
I seem to recall that the elements might be slightly different in structure for the wls700 version of the DTD, so please check that (I cannot, I'm at home and don't have everything here).
Give that a try and see if it doesn't solve your compilation failure.
Also, the compilation should not be throwing a null pointer exception in a case like that, I consider that to be a bug.
-thorick

Using a BLOB data type in a CMP Entity Bean??

Hi all,
i am trying to store blob type data using entity bean, The corresponding field in the Entity bean is defined with data type byte[ ] , and i'm getting error while creating entity bean, could anyone please help me!
This is the error:
[6/7/06 11:19:05:559 EEST] 5b7936b5 ExceptionUtil E CNTR0019E: Non-application exception occurred while processing method "create". Exception data: com.ibm.ejs.container.CreateFailureException: ; nested exception is:
     javax.ejb.EJBException: nested exception is: com.ibm.ws.ejbpersistence.utilpm.PersistenceManagerException: PMGR6022E: Error using adapter to create or execute an Interaction. com.ibm.ws.rsadapter.cci.WSInteractionImpl@6593f6a7
javax.ejb.EJBException: nested exception is: com.ibm.ws.ejbpersistence.utilpm.PersistenceManagerException: PMGR6022E: Error using adapter to create or execute an Interaction. com.ibm.ws.rsadapter.cci.WSInteractionImpl@6593f6a7
com.ibm.ws.ejbpersistence.utilpm.PersistenceManagerException: PMGR6022E: Error using adapter to create or execute an Interaction. com.ibm.ws.rsadapter.cci.WSInteractionImpl@6593f6a7
     at com.ibm.ws.ejbpersistence.dataaccess.DataAccessRequestImpl.execute(Unknown Source)
     at com.ibm.ws.ejbpersistence.beanextensions.ConcreteBeanStatefulInstanceExtensionImpl.executeCreate(Unknown Source)
     at com.ibm.ws.ejbpersistence.beanextensions.CBNotExistState.ejbCreate(Unknown Source)
     at com.ibm.ws.ejbpersistence.beanextensions.ConcreteBeanStatefulInstanceExtensionImpl.ejbPostCreate(Unknown Source)
     at org.epo.dg3.task.ConcreteDocStore_5418fe50.ejbPostCreate(ConcreteDocStore_5418fe50.java:133)
     at org.epo.dg3.task.EJSCMPDocStoreHomeBean_5418fe50.create_Local(EJSCMPDocStoreHomeBean_5418fe50.java:29)
     at org.epo.dg3.task.EJSLocalCMPDocStoreHome_5418fe50.create(EJSLocalCMPDocStoreHome_5418fe50.java:23)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.ibm.etools.utc.model.ReflectionMethodModel.invoke(ReflectionMethodModel.java:68)

Try to use the OCI native driver instead of THIN.

How to delete a database record by using EJB entity beans

Hi, All,
Does anyone know how to use entity bean to delete a database record? I have all the EJB entity beans created, including access beans to each. I can successfully create records, find and update records, however, I haven't find a way to delete records yet.
Your response is appreciated.
Cathy

Please see EJB Forums for continue discussion on this subject.
Reference titile: "how to delete database record by using CMP entity beans "

How can i design a EJB application using session Beans?

Hello,
I am designing a Find application using EJB. Here a user is prompted a search page, where he can enter the search criteria's. Then on click of submit, the query is formed at the server side depending on what criteria's were selected. Then a jdbc query is performed and the results are returned back to the user. Here no session is maintained for the users. Can anyone suggest me how to design this application using EJB. Should i use entity beans for this or session beans will suffice? Should the jdbc query be performed in the bean itself or should it be outside in a helper class? Please kindlu suggest me the design for this application...
Regards,
Subbu

Hi,
First of all, I'm unable to figure out why you need to use EJB for this scenario. You can write a helper class to frame and execute the query.
If you really want to use EJB, then I suggest you use a stateless Session Bean with transaction attribute as TX_NOT_SUPPORTED. From the session bean, you can call the helper class. But, by avoiding the session bean, you can eliminate remote calls, thus improving your performance. Also, check if the database & the db driver you are using supports sql caching.
Regards,
Raj.

Entity bean with primary key generated by trigger

Hi,
We have a table(oracle) with one column as primary key,
but the primary key is generated by trigger every time
a new row is inserted into this table, inside the trigger,
it uses oracle sequence to get the next val.
If we want to use entity bean with it, what should we specify, it's not application-managed primay key, it's
not auto-generated primary key either. How can we resolve
it without change the database part.
Any thought is appreciated.
Thanks
afang

The code is already there with JDBC call inserting
into the table, the inserting trigger then will generate
sequence key and being inserted into primary key column.
Now wondering if it's possible to change the code to use entity bean but without modifying the trigger (since it contains other business logics).

Regarding ENTITY bean local interfaces

Hi all,
I have a component session bean - containing a number of service methods for creating, retrieving, updating & deleting instances of a related entity bean. This session bean is used by another session facade bean, which invokes the various service methods in some sequence to complete a major task.
In the component session bean, the retireve methods return the local interface of the entity bean - on which it operates. The update methods accespt local interfaces of entity bean which can be directly updated.
My question is : Is it a right approach to pass the entity bean instances between method calls.
Thanks in advance,
Baskar

Your pointers regarding pt 2 was nice. Thanks.
This being my first J2ee design, I'am just collecting as much information as possible to stay confident.
Later, I started thinking a bit more regarding pt 1.
Where, I decided using individual session beans for different components(representing unique functionalities).
i.e,, I'am just thinking, should I use individual session beans for each of these different components.
What if I use standard java classes - implementing pre-defined interfaces for each of these components & use the components through these interfaces in session facade.
Now, I'll be using entity bean creates/retrieves/updates/deletes from inside normal java classes.
I thought, this would obviate the need for JNDI lookups - each time I want to use the components in my session facade.
But, I'am not sure of where this will impact..As far as I can visualize, this seems to be normal. Please share ...your thoughts regarding this. (something regarding transactions ??)

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.

Disadvantages of using entity beans.

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