CMP vs BMP

hi friends
coud any tell me the core benefits/asvantages of using CMP beans on the BMP ot vice versa!!!
or any disadvantage of using any specific type... with that were should be use the CMP and where BMP
thxs!

CMP is advantegous for portability. The sql statement/parameter/tuning is done outside the java code. Very good approach if you are J2EE component vendor because your client may not use to Bea, IBM, Sun, or XXXXX product.
BMP is adventegous if you know how to tune the sql by hand, by assumption that your tuned-by-hand sql far overperform the performance of CMP's SQL, otherwise CMP is still recomended. People won't use this approach if they sell J2EE component, why? Not everyone will use WebLogic+Oracle but your code is optimized for WebLogic+Oracle.
Please pardon my bad english.

Similar Messages

Could I build 1:N relationship between CMP and BMP?

Hi, as subject, Could I build 1:N relationship between CMP and BMP?
Thanks a lot!
a13519

Container managed relationships only apply to CMP beans. You can look at the DTD in appendix B of the EJB spec or chapter 10 where they make this distinction.

Nobody knows this fundamental question - CMP, CMT, BMP, BMT. Surprised !!

Hello,
I've talked to many experts and read books on EJB but none of them gave me a clear cut answers. What are the definitions of CMP, CMT, BMP and BMT? No one could explain "Persistent" from "Transaction" properly. No books clearly define them at all. Some say BMP means BMT and CMP means CMT. Some others say they are totally different concept. Others even say different stories. Actually, when we create EJBs (in Visual Cafe as an example), we can tell whether the bean is CMP or BMP but there os no place where we can define the transaction mode (BMT or CMT). How come do so many people get confused about this fundamental concept? Can anybody explain them clearly please?

CMP = Container Managed Persistence
This means that the container (part of the EJB Server) automatically handles persisting your bean to a DB. So if you have an Entity Bean, for example, that has some properties (like name, size) and a table in the database with the fields name (as a varchar), size (as an integer), then when you set the bean's properties to "Joe" and "14", you can then look in your database and those values will be there. You (the developer) do not have to write any code to put those values into the DB.
BMP = Bean Managed Persistence
This means that (in the above example of an EJB with properties name, size), if you set your bean's name to "joe" and size to 14, those values will NOT go into the DB unless you (the developer) put them there.
CMT = Container Managed Transactions
A transaction is really either one statement (or action) or a bunch of them that are grouped together. If it is a group, then for any one of them to be executed / committed, they must all execute successfully. If even just one of the actions / statements fails, they all fail (or are all "rolled back", i.e. un-done)
CMT means that the container (EJB Server) will handle making sure that all the actions or statements from a transaction (i.e. a particular context of actions kicked off when an EJB is called) are completed successfully. If they are, the container will commit (execute) all the statements and return "success". If any one of them fails, the container will handle rolling back (un-doing) all the statements. This is VERY useful, as you do not need any special if statements or try-catches, the container does it for you.
BMT = Bean Managed Transaction
This means that you (the developer) will have to logically group together all that actions that you consider for a transaction. If any one of them fails, you will need to make sure all of them are rolled back and that "failure" is returned to the caller. If they are all successful, you will have to return success.
You can do this by using the below code:
(in all the code below, they may wrap from one line to the next, just pay attention to where the ";" is)
//import Transaction
import javax.transaction.UserTransaction
//make a new transaction:
UserTransaction userTran = ( UserTransaction ) initialContext.lookup("java:comp/UserTransaction");
try
//And then marking the beginning of the transaction:
userTran.begin();
//Then Do your stuff (i.e. the actions)
myPersonalBusinessMethods();
//commit the transaction cause it's all ok
userTran.commit();
catch (Exception e)
//rollback (un-do) all the stuff cause error occurred
userTran.rollback();
Hope all this helped and finally explained it! Feel free to throw some duke dollars my way if it did! ;P
Robert

Which should I use (CMP or BMP) for my Web Application?

I am developing an Web Application with Oracle Database. In this work, I always use the SQL sentences in complex (Joining many tables with WHERE condition). So that, I want to be adviced in developing this web application with CMP or BMP or other opinions?
Thanks in advance!

If you want to write long (optimized) SQL queries, than you shouldnt use
entity EJB's at all.

CMP and BMP configure for deploying in weblogic

how to run CMP and BMP in weblogic and configure in welogic
tell me the steps to be followed for connection pooling and deployement and configure in weblogic builder....

Disagree that CMP is always better than BMP. CMP is in reality merely an implementation of BMP that provides a declarative method of providing a persistence layer. You could easily use other declarative systems to provide the same service, but you are alway relying on BMP and when CMP fails to provide you need to return to the raw BMP.
It a bit like the difference between high/low level languages. We don't normally write direct assembly (yes, I am aware that real programmers yada yada yada) but we do use it, and sometimes you actually have to write it for specialised applications - most notably for high performance.
Both have their pluses and minuses, and you need to know when to use one over the other.

CMP and BMP in application

I am new to EJB, please help me on this:
Can i have mix of CMP and BMP in my application?
Is it best enforce that all entity bean in either one but not both?

You are impling that BMP is DB-dependent. The SQL generated by the >Container is nothing magical. It is no more DB independent than SQL >written by the developer. You don't have to be DB-specific to use BMP, >but you do have to be appserver-specific to use CMP.By Db independent I mean that the sql code for container call back methods is generated by Container. You dont have to do anything. If you are deploying bean for oracle or sql , container will take care for that. Refer to the specs There is brief para on advantages of CMP.
For BMP you have to change the code according to the database. Container will not do anything for that.
"2. Reduced development efforts."
Yes, marginally, but the reduction in initial development time must >be weighed against:
The tools (or lack thereof) provided to map the beans to the tablesWell even if you are working with BMP you have to be aware of that. There are various performance improvement setting which are app server specific. It doesnt matter if you are using BMP or CMP for that matter
The time spent dealing with appserver vendors when things don't workOfcourse this happens with BMP also.
The inherent limited flexibility of CMPAlmost 90 % of the scenarios can be delt with CMP. Yes if not you can use BMP.
Also if time is such a factor, you should probably be generating your >beans (either CMP or BMP). This eliminates the development effort >difference between them. Of course that means developing BMP will be >faster since you don't have to muck about with the appserver, mapping >beans, marking methods as read-only, etc.Ha... I cannot take it. In general I can say It doesnt matter if you are using BMP or CMP , you have to be aware of different performance and other settings which are app server specific.
Remember CMP is available for 2 reasons:
1) So you can minimize development effort on simple Object-to-RDB >mappingsThey now support various relationships like 1-1,1-many, many-many
2) So that the big vendors (IBM, BEA, etc.) who were involved in >drafting the spec can provide "features" not in the specification, >encouraging vendor lock-in. Any Specification is not complet or exaustive. Vendors need to fill the gap.
--Ashwani

CMP and BMP

hi there,
is this true?
CMP -> JTA
BMP -> EJBContext.getUserTransaction
note: CMP uses JTA to do transaction but BMP uses EJB api to do transaction handling.
Thanks
Neo

Disagree that CMP is always better than BMP. CMP is in reality merely an implementation of BMP that provides a declarative method of providing a persistence layer. You could easily use other declarative systems to provide the same service, but you are alway relying on BMP and when CMP fails to provide you need to return to the raw BMP.
It a bit like the difference between high/low level languages. We don't normally write direct assembly (yes, I am aware that real programmers yada yada yada) but we do use it, and sometimes you actually have to write it for specialised applications - most notably for high performance.
Both have their pluses and minuses, and you need to know when to use one over the other.

How to get connection when mixing cmp with bmp

Hello,
I have a CMP-based system in which I need to have a method in a
stateless session bean to use BMP. In order for that method to
participate in a larger transaction, I need to make sure that I grab
the database connection that is used by that transaction. How would I
do that?
For simple BMP, I would get my connection like this
InitialContext ctx = new InitialContext();
DataSource ds = (javax.sql.DataSource)ctx.lookup("java:/someDataSource");
java.sql.Connection conn = ds.getConnection();
But in this case, how can I be sure that the connection I got is the
one that is used by the current transaction? Or does it happen
auto-magically?
I have pored thru the API and can't seem to find a way to get a
Connection from a javax.ejb.SessionContext, which I do have a handle
to.
Thanks in advance,
Chishun Kwong

[email protected] (Chishun Kwong) wrote in message news:<[email protected]>...
Hello,
I have a CMP-based system in which I need to have a method in a
stateless session bean to use BMP. In order for that method to
participate in a larger transaction, I need to make sure that I grab
the database connection that is used by that transaction. How would I
do that?
For simple BMP, I would get my connection like this
InitialContext ctx = new InitialContext();
DataSource ds = (javax.sql.DataSource)ctx.lookup("java:/someDataSource");
java.sql.Connection conn = ds.getConnection();
But in this case, how can I be sure that the connection I got is the
one that is used by the current transaction? Or does it happen
auto-magically?
I have pored thru the API and can't seem to find a way to get a
Connection from a javax.ejb.SessionContext, which I do have a handle
to.
Thanks in advance,
Chishun KwongI realize after posting this message that this is actually kind of a
dumb question. This has nothing to do with mixing BMP and CMP, even in
pure BMP, you have to wonder if the connection you get is the one used
by the current transaction (if there is one already), and of course it
is the container's responsibility to make sure.
CSK

Default Isolatioin level in CMP and BMP

Hi All,
If we don't set isolation in a descriptor (in case of CMP) then what is the default level ?
and what is the default level in case of BMP?
Is it a Database dependent?

Hi,
Didnt find this reference in any books/pdf?
Did u find the same?
Seetesh
isolation-level defines a valid transaction isolation level to apply to specific EJB
methods. The following are possible values for isolation-level:
TransactionReadUncommitted:: The transaction can view uncommitted updates from other transactions.
TransactionReadCommitted: The transaction can view only committed updates from other transactions.
TransactionRepeatableRead: Once the transaction reads a subset of data, repeated reads of the same data return the same values, even if other transactions have subsequently modified the data.
TransactionSerializable: Simultaneously executing this transaction multiple times has the same effect as executing the transaction multiple times in a serial fashion.
For Oracle databases only:
TransactionReadCommittedForUpdate
TransactionReadCommittedForUpdateNoWait

CMP?? BMP??

BMP ?? isnt it bitmap format?? haha
But after I have seen one of the discussion in the forum, I began to wonder what is CMP and what is BMP??
thanx

Hi ,
As far as my experience goes , I would suggest you that try writing CMPs unless u have very less choice to go for BMPs ......CMPs are always faster than BMPs and are also maintainable.
BMPs always operate in 2 stages ....
- Finding the record in the database and retrieving the primary key
- Retrieving the record data into the buffer ..
CMP allows for optimizing these two database accesses into a single database access whenever it makes sense to do so, allowing retrieval of both the key and the record data in one database call.
But as far as possible , try writing BMPs extending from CMPs . Have your business methods in CMPs and use DAO pattern. And BMPs will only be meant for methods doing database searches which are necessary for BMP (i.e. ejbcreate , ejbstore etc.) .
Please go to the following link and it discusses all the issues which u might be needing in deciding between CMPs and BMPs.
http://developer.java.sun.com/developer/technicalArticles/ebeans/sevenrules/
I suggests u following thing also which are not part of your query -
If u are doing heavy searches , try avoiding entity beans and instead use stateless session beans.
Thanks
- amit

BMP vs CMP

Hi All,
This was one of the questions asked to my friend in an interview. What are the differences between CMP and BMP and on what basis you decide to opt for CMP or BMP ?

Both of these concepts refer to persisting the data into the Database. With BMP as it is named - Bean Managed Persistence - the EJB developer needs to write all the DB routines used to access DB, store and retrieve data to/from DB and also implement any Finder methods defined in the Remote/Local interfaces. Also the relationships need to be implemented programmatically.
With CMP - Container Managed Persistence - the EJB Developer need not worry about the implementation of the DB routines. He/she only needs to define the methods and fields as 'abstract' and the rest should be taken care of by the Container. How does the Container take care of these? Well, the deployment descriptor (ejb-jar.xml) is the place where you will define the CMP fields and also the CMR relationships and also EJB-QL scriptlets for the finder and select methods
CMP is much easier considering different aspects of development. CMP allows portability in that we dont have worry about the underlying datastore since queries are written in EJB-QL which acts on a layer over the underlying DB.
HTH

Can I use oracle blob by CMP bean in weblogic 6?

I use weblogic 6.1(sp3) and Jbuilder 7.when I try to use oracle blob by CMP bean,the
errors are:
javax.ejb.FinderException: Exception raised in findByPrimaryKey
java.io.StreamCorruptedException: InputStream does not contain a serialized object
What should I do?Is there examples about using oracle blob?
thanks a lot!

Great! So what was the problem?
Regards,
Slava Imeshev
"Roger Lee" <[email protected]> wrote in message
news:[email protected]...
>
Finally got it working with CMP, which is my preferred choice (over BMP).
I read the Excel Spreadsheet into a "byte []" array, and the Entity Beanmapped
"byte []" to the Blob column in the Oracle table.
"Slava Imeshev" <[email protected]> wrote:
Roger,
I'm not quite sure I undestand the problem. Could you:
1. Post deployment descriptors in part related to this
CMP bean?
2. Post the piece of code that is failing?
Please post the information above and we will help
you to hunt the problem down.
No, I don't have any problems accessing blobs
from CMP.
Regards,
Slava Imeshev
"Roger Lee" <[email protected]> wrote in message
news:[email protected]...
Yes. I have added;
<dbms_column-type>OracleBlob</dbms-column-type>
It fails because the locater to the blob, obtained by findBYPrimaryKeyis
null.
i.e. an empty_blob() is not created.
Have you got CMP to access Blobs in WLS 6.1?
"Slava Imeshev" <[email protected]> wrote:
Hi Roger,
Have you tried using OracleBlob as dbms-column-type?
Also, could you post that part of your code that is failing?
Regards,
Slava Imeshev
"Roger Lee" <[email protected]> wrote in message
news:[email protected]...
I can access Clobs using CMP. If you are using the Oracle OCI Driveryou
do not
need to add this line.
However if you are using the Oracle Type 4 Thin drivers you need
to
add;
<dbms_column-type>OracleClob</dbms-column-type>
to the file;
weblogic-cmp-rdbms-jar-xml
This DOES NOT work with Blobs.
I am unable to get WebLogic 6.1 sp4 persist a Blob to an Oracle
8.1.x
table and
retrieve it using either CMP or BMP.
Unless any one show me a complete working CMP and BMP example?
Roger Lee
Deepak Vohra <[email protected]> wrote:
BLOB and CLOB DBMS Column Support for the Oracle DBMS
http://edocs.bea.com/wls/docs61/ejb/cmp.html#1061636
shybird wrote:
I use weblogic 6.1(sp3) and Jbuilder 7.when I try to use oracle
blob
by CMP bean,the
errors are:
javax.ejb.FinderException: Exception raised in findByPrimaryKey
java.io.StreamCorruptedException: InputStream does not contain
a
serialized
object
What should I do?Is there examples about using oracle blob?
thanks a lot!

Adding a column to a DB table with CMP entities

Morning all.
I've been asked whether adding a column to a database table will break the CMP entity bean (EJB2) associated with the table. I suspect that it won't and that the new field will be ignored. Another developer here says that it will no longer compile (I can't see how this could be the case but still...) and I can find no evidence to either refute or corroborate either position.
Can anyone tell me for definite - if we add a column to a database table mapped to a CMP entity bean, will we HAVE to update the bean, or can we leave it ignorant of the new column?
(For the purposes of the question, please assume that the column has no constraints i.e. can be null etc.)
Thanks in advance
-- kaideejee
Message was edited by kaideejee : CMB entities? What are they? Typo fix.

Well alterations(adding / removing a column) to the
table should be made available to the bean
irrespective of the persistance(CMP OR BMP) or normal
bean with your own methods that depicts the
behaviour.
reason is simple: probably bean may/may not contain
the corresponding setter or getter or finder methods
related to the ALTERED TABLE(NEW COLUMN)The reason for what is simple? Sorry I may have missed your point there. Are you saying that it's correct practice to make it available to the bean, or that it will be made available behind the scenes, subject to getters/setters being created?
Assuming we choose not to create these getters and setters (we have a horrible hybrid monster which uses stored procedures for some things and EJB for others, so it's feasible that the EJB end may not need to see some fields used by other parts) would the entity beans continue to play nicely with the database rows, or would the additional columns throw it completely?
Cheers
-- kaideejee

Help reg. read only CMP bean in the examples!!

Hi,
I have been working with examples of EJB in WLS 6.1
I used the Access database with CMP.
The basic entity beans, both CMP and BMP worked well.
However when I tried the read-only Stock Bean and write StockWriter Beans... I received the following error... I am not sure what does it say...
==============================================
Beginning readMostly.Client...
Creating a StockWriter for BEAS
There was an exception while creating and using the Beans.
This indicates that there was a problem communicating with the server: java.rmi.RemoteException: EJB Exception:; nested exception is:
java.sql.SQLException: [Microsoft][ODBC Microsoft Access Driver]Optional feature not implemented
Start server side stack trace:
java.rmi.RemoteException: EJB Exception:; nested exception is:
java.sql.SQLException: [Microsoft][ODBC Microsoft Access Driver]Optional feature not implemented
java.sql.SQLException: [Microsoft][ODBC Microsoft Access Driver]Optional feature not implemented
at sun.jdbc.odbc.JdbcOdbc.createSQLException(JdbcOdbc.java:6026)
at sun.jdbc.odbc.JdbcOdbc.standardError(JdbcOdbc.java:6183)
at sun.jdbc.odbc.JdbcOdbc.SQLBindInParameterFloat(JdbcOdbc.java:852)
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.setLong(JdbcOdbcPreparedStatement.java:575)
at weblogic.jdbc.pool.Statement.setLong(Statement.java:369)
at weblogic.jdbc.rmi.internal.PreparedStatementImpl.setLong(PreparedStatementImpl.java:114)
at weblogic.jdbc.rmi.SerialPreparedStatement.setLong(SerialPreparedStatement.java:147)
at ejb.readMostly.StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.__WL_create(StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.java:589)
at ejb.readMostly.StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.ejbCreate(StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.java:518)
at java.lang.reflect.Method.invoke(Native Method)
at weblogic.ejb20.manager.DBManager.create(DBManager.java:519)
at weblogic.ejb20.manager.DBManager.remoteCreate(DBManager.java:489)
at weblogic.ejb20.internal.EntityEJBHome.create(EntityEJBHome.java:190)
at ejb.readMostly.StockWriterBean_u4qwd5_HomeImpl.create(StockWriterBean_u4qwd5_HomeImpl.java:78)
at ejb.readMostly.StockWriterBean_u4qwd5_HomeImpl_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:305)
at weblogic.rmi.cluster.ReplicaAwareServerRef.invoke(ReplicaAwareServerRef.java:93)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:274)
at weblogic.rmi.internal.BasicExecuteRequest.execute(BasicExecuteRequest.java:22)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
End server side stack trace
; nested exception is:
java.sql.SQLException: [Microsoft][ODBC Microsoft Access Driver]Optional feature not implemented
Start server side stack trace:
java.sql.SQLException: [Microsoft][ODBC Microsoft Access Driver]Optional feature not implemented
at sun.jdbc.odbc.JdbcOdbc.createSQLException(JdbcOdbc.java:6026)
at sun.jdbc.odbc.JdbcOdbc.standardError(JdbcOdbc.java:6183)
at sun.jdbc.odbc.JdbcOdbc.SQLBindInParameterFloat(JdbcOdbc.java:852)
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.setLong(JdbcOdbcPreparedStatement.java:575)
at weblogic.jdbc.pool.Statement.setLong(Statement.java:369)
at weblogic.jdbc.rmi.internal.PreparedStatementImpl.setLong(PreparedStatementImpl.java:114)
at weblogic.jdbc.rmi.SerialPreparedStatement.setLong(SerialPreparedStatement.java:147)
at ejb.readMostly.StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.__WL_create(StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.java:589)
at ejb.readMostly.StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.ejbCreate(StockWriterBean_u4qwd5__WebLogic_CMP_RDBMS.java:518)
at java.lang.reflect.Method.invoke(Native Method)
at weblogic.ejb20.manager.DBManager.create(DBManager.java:519)
at weblogic.ejb20.manager.DBManager.remoteCreate(DBManager.java:489)
at weblogic.ejb20.internal.EntityEJBHome.create(EntityEJBHome.java:190)
at ejb.readMostly.StockWriterBean_u4qwd5_HomeImpl.create(StockWriterBean_u4qwd5_HomeImpl.java:78)
at ejb.readMostly.StockWriterBean_u4qwd5_HomeImpl_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:305)
at weblogic.rmi.cluster.ReplicaAwareServerRef.invoke(ReplicaAwareServerRef.java:93)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:274)
at weblogic.rmi.internal.BasicExecuteRequest.execute(BasicExecuteRequest.java:22)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
End server side stack trace
End readMostly.Client...
==========================================
please help
SP
[att1.html]

<entity-cache>
          <max-beans-in-cache>...</max-beans-in-cache>
          <read-timeout-seconds>...</read-timeout-seconds>
          <concurrency-strategy>ReadOnly</concurrency-strategy>
          </entity-cache>
          I believe this is what you are looking for and this is part of entity-descriptor.
          -- Prasad
          Aruna wrote:
          > Hi
          > I am trying to develop few entity beans which is for only reading the
          > data from the data base, As Read only entity beans are treated like stateless
          > session beans(ie lead balancing at method calls as well auto failover) in the
          > cluster. I want to know how to specify an entity bean as read only entity bean???
          > ie in deployment descriptor so that ejb container treats it as a read only entity
          > bean.
          >
          > Any help on this highly appreciated
          >
          > Thanks and Regards
          > Aruna

What type of Container Persistence should I choose �?

Hi,
I would like to know... what type of persistence should I choose to manage the entities bean.
At first I choose CMP because it seems to be much easy to understood and maintain, and it seems to work fine with small queries...
Every record of a table of muy RDBMS is represented by CMP Bean... �? is it true �?
What happens if i will like to extract a big table with thousands and thousands records �? does this, affects to the performance of my server �? how can i control...�?
Can I make complex queries with the CMP beans or should i use BMP beans in this case �?
I do not know if the ejb-ql language will result helpful to perform complex queries...
Can you help me �?
Thank you....

Hi,
I would like to know... what type of persistence
should I choose to manage the entities bean.CMP or BMP - those are the two choices.
>
At first I choose CMP because it seems to be much easy
to understood and maintain, and it seems to work fine
with small queries...
Every record of a table of muy RDBMS is represented
by CMP Bean... �? is it true �?True.
>
What happens if i will like to extract a big table
with thousands and thousands records �? does this,
affects to the performance of my server �? how can i
control...�?Yes, indeed, it does affect performance.
One way to handle that is to use a session bean to access all the data at once and then send back a collection of objects. There's a Core J2EE pattern called session facade that can help:
http://java.sun.com/blueprints/corej2eepatterns/Patterns/SessionFacade.html

CMP vs BMP

Similar Messages

Maybe you are looking for