About entity bean

HI, does entity bean exsit in CE7.1 SR5? I can not find it.

Snehal,
Not quite correct. EJB 3.0 still supports entity beans, they are not removed and not even officially "deprecated". But you're right to some extent - JPA is now the preferred and recommended persistence technology for Java EE (and also Java SE).
BTW: No JEE - it's Java EE
Cheers,
Vladimir

Similar Messages

Questions about entity bean caching/pooling

We have a large J2ee app running on weblogic6.1 sp4. We are using entity beans
with cmp/cmr. We have about 200 EntityBeans and accessed quite heavily. We are
struggling with what is the right setting of max-beans-in-cache and idle-time-out.
The current max heap setting is 2GB. With the current setting (default setting
of max-beans-in-cache to 1000, with a few exceptions to take care of cachefullexceptions)
we run into extended gc happening after about 4 hours. The memory freed gradually
reduces with time and lurks around the 30% mark after about 4 hours of run at
the expected load. In relation to this we had the following questions
1. What does caching mean?
a. If a bean with primary key 100 exists in the cache, and the following
is done what is expected
i. findByPrimaryKey(100)
ii. findBySomeOtherKey(xyz)
which results in loading up bean with primary key 100
iii. cmr access to bean with
primary key 100
Is the instance in the cache reused at all between transactions?
If there is minimal reuse of the beans in cache, Is it fair to assume that caching
can only help loading of beans within a transaction. If this is the case, is there
any driver to increase the max-beans-in-cache other than to avoid CacheFullException?
In other words, is it wrong to say that max-beans-in-cache should be set to the
minimum value so as to avoid CacheFullExceptions.
2. Again what is the driver of setting idle-time-out to a value? ( We currently
have it at 30 secs) Partly the answer to this question would again go back to
what amount of reuse is done from cache? Is it right to say that it should be
set to a very low value? (Why is the default 10 min?)
3. Can you provide us any documentation that explains how all this works
in more detail, particularly in relevance to entity beans. We have already read
the documentation from weblogic as is. Anything to give more explicit detail?
Any tools that can be of use.
4. What is the right parameter (from among the things that weblogic console
throws up) to look at for optimizing?
Thanks in advance for your help
Cheers
Arun

The behaviour changes according to these descriptor settings: concurrency-strategy,
db-is-shared and include-updates.
1. If concurrency-strategy is Database, then the database is used to provide locking
and db-is-shared is ignored. A bean's ejbLoad() is called once per transaction,
and the 'cache' is really a per-transaction pool. A findByPrimaryKey() always
initially hits the db, but can use the cache if called again in the same txn (although
you'd simply just pass a reference around). A findByAnythingElse() always hits
the db.
2. If concurrency-strategy is ReadOnly then the cache is longer-term: ejbLoad()
is only called when the bean is activated; thereafter, the number of times ejbLoad()
is called is influenced by the setting of read-timeout-seconds. A findByPrimaryKey()
can use the cache. A findByAnythingElse() can't.
3. If concurrency-strategy is Exclusive then db-is-shared influences how many
times ejbLoad() is called. If db-is-shared is false (i.e. the container has exclusive
use of the underlying table), then the ejbLoad() behaviour is more like ReadOnly
(2. above), and the cache is longer-term. If db-is-shared is true, then the ejbLoad()
behaviour is like Database (1. above).
Exclusive concurrency reduces ejbLoads(), increases the effectiveness of the cache,
but can reduce app concurrency as only one instance of an entity bean can exist
inside the server, and access to it is serialised at the txn level.
You can't use db-is-shared = false in a cluster. So Exclusive mode is less useful.
That's when you think long and hard about Tangosol Coherence (http://www.tangosol.com)
4. If include-updates is true, then the cache is flushed to the db before every
non-findByPrimaryKey() finder call so the finder (which always hits the db) will
get the latest bean values. This overrides a true setting of delay-updates-until-end-of-tx.
The max-beans-in-cache setting refers to the maximum number of active beans (really
beans that have been returned by a finder in a txn that hasn't committed). This
wasn't checked in SP2 (we have an app that accidently loads 30,000 beans in a
txn with a max-beans-in-cache of 3,000. Slow, but it works, showing 3,000 active
beans, and 27,000 passivated ones...).
This setting is checked in SP5, but I don't know about SP4. So you do need to
size appropriately.
In summary:
- The cache isn't nearly as useful as you'd like. You get far more db activity
with entity beans than you'd like (too many ejbLoads()). This is disappointing.
- findByPrimaryKey() finders can use the cache. How long the cache is kept around
depends on concurrency-strategy.
- findByAnythingElse() finders always hit the db.
WebLogic 8 tidies all this up a bit with a cache-between-transactions setting
and optimistic locking. But I believe findByAnythingElse() finders still have
to hit the db - ejbql is never run against the cache, but is always converted
to SQL and run against the db.
Hope this is of some help - feel free to email me at simon-dot-spruzen-at-rbos-dot-com
(you get the idea!)
simon.

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.

Some problems about entity bean

As what I learnt from books, client uses primary key for getting instance of entity bean. However, if I want to create some entity beans for read only purposes. That is, I will not has the process of bean instantiation from client side directly. What should that object be existed in my system. As they are persistent, they will not be value object. Would you give me some suggestions?

If you want to create some entity-bean instances in order to read the data from the database, you should you find method insteads of create method. If you want to ADD new row in the table then use create method.
If you want to read, it is better to used session bean, and get the RowSet from ResultSet(jdbc)(Please don't update the data in RowSet it will update the database but the entity bean when you do it).
I hope I understand your question correctly and you understand what my words too.

Basic question about Entity Bean.

Hi:
Let's suppose that we have the code like below:
     home = (ProductHome)javax.rmi.PortableRemoteObject.narrow(ctx.lookup("ProductHome"),
ProductHome.class);
     home.create("mouse");
     home.create("keyboard");
     home.create("monitor");
     home.create("mainboard");
Q1: Does the weblogic hold the four instances of Product Bean after run those
code?
Q2: When do the instances will be backed to pool or be destoryed?
Q3: Does the weblogic will ready all beans if client execute home.findByALL().
(findByAll method return all product), that will consume a lot of memory if there
is a mass of client do that?
Regards!
Eric Temel

"Michael Jouravlev" <[email protected]> wrote in message
news:[email protected]..
>
"Eric Temel" <[email protected]> wrote in message
news:[email protected]..
Q3: Does the weblogic will ready all beans if client executehome.findByALL().
(findByAll method return all product), that will consume a lot of memoryif there
is a mass of client do that?WL has a setting which allows you to find a bean without loading it.Search
docs.
ah, good point. To be redundant, even though the beans are found and not
loaded (via the finders-load-bean DD setting which I think we're referring
to),
the 'found' but unloaded beans will still take up a some room in the entity
bean cache.
Something to keep in mind if memory is an issue..
-thorick

Need help about entity bean relationshi

I have two entity bean,userBean(userid,username,password,email)and subscriptionBean(email,subtopic).so email column is FK,right?
but both email,subtopic fields in subscriptionBean are NOT set to be unique,i mean there should be many same email address with difference subtopic subscriptions.
so NO primaryKey in my second entity bean.is it OK?

Hello,
Your EJB MUST have a primary key !, so add a field ( maybe subscriptionId) to you bean which will be unique.
Regards,
Sebastien Degardin.

Entity beans live long time?????

Hi,
What i undestood about entity bean persitence is like this.The create methos of an
entity bean will create a record in databse and populate the data whenever it's required(i mean even updation of data using ejbstore()).
But i can create a record using session bean also and can do what ever an entity bean does.Now my doubt is,what they mean by entity bean is persistent and it will live long time in system?
Thanks in advance

hey, u didn't get the concept right
whenever u invoke a bean method in session bean, it will create a session and will persist till u close the session. In between if sys crashes then ur session is lost. so if u r invokin the bean method again, then again u hv to create the instance.
whereas if entity bean, then ejbload and ejbstore methods will put the instances in the databses. therefore, if sys crashes, only thing is u hv to call the ejbload method to call the instance, so u can start from where u hv left, and not to start the whole process again.
hope u understand.
u can appreciate this deifference when u will write very large codings.
bye

Question about multiple RequiresNew in Entity Bean transaction

Hi I've got a problem concerning transactions:
In both cases I've got a CMP Entity Bean called "Account" with some mothods like
increaseBalance(double amount)
decreaseBalance(double amount)
transferMoney(double amount)
for all methods the TransactionAttribute is "RequiresNew". When calling first decreaseBalance(amount) and afterwords
increaseBalance(amount), bothfrom within transferMoney(amount). When setting entityContext.RollbackOnly()
I would expect this rollback doesn't undo my changes because they are in a different transaction, which has been comitted
when the methods finished, but both are rolled back.
I thought there are no "nested transactions" in J2EE. Isn't this one?
Thanks!
Martin

Ahhhh! Right! If I call "this.increase(balance)" from the AccountBean method "transferMoney", the container has no chance to create a new transaction, so the same transaction as in "transferMoney" is used. I didn't think about that, but of course...
So one should never call a bean method directly even when it is a method of the same instance the thread is currently in.
Thanks a lot!

Query about reentrant in ejb-jar.xml file(in case of entity Bean)

Hi all friends,
I am new to EJB I couldn't understand in ejb-jar.xml file in case Entity Bean[<reentrant>False</reentrant>
&<reentrant>true</reentrant>]what is the function of this tag and what is the effect of value true and false of this tag.Can any one please explain it.
Regards
Bikash

Hi,
Re-entrant tag is used in the ejb-jar.xml to notify the container if you would want your bean to call itself through another bean.
Most of the time you would want it to be set to FALSE because you would have to consider the multi-threading issues if you set it TRUE.
Regards
Meka Toka

Which is the way to take JNDI info about some Entity Bean????

I'm trying to take the JNDI reference of an Entity Bean for using in a lookup method in a dimanical way. i.e I have to choose one of any possible Entity Beans depending of the JNDI reference of them.
Any help needed...
Thank you.

Friend,
Did you try looking at the XML deployment descriptors? You can see there <ejb-name>
Ramgopal

Help about Date and Time by CMP entity bean

I should have two fields in my cmp .one stores current date ,another one stores current time while ejbcreate();
I should be able to get findmethod findobjectBetween ?! and ?2
or that sorts of find method.what type of the method should I use.
java.util.Date or Simply String?
if I use java.tuil.Date as the type.
How shoud my ejbcreate method look like?
public abstract void setDate(Date mydate);
public abstract Date getDate();
ejbCreate(String name,String password,Date mydate,Date mytime)
setDate()
I suppose I use write a business method getCurrentDate() which uses
java.util.Date().toLocale,But I think it just returns String
help pls.

I am using oc4j(Oracle9iAS (9.0.3.0.0))
I am getting the following error using Timestamp while deploying cmp entity bean ejb1.1. Thanks...
Auto-deploying TimestampTestEntity.jar (No previous deployment found)... TimestampTest_EntityBeanWrapper0.java:1558: Missing term.
if (if(thread.contextContainer != null)
^
TimestampTest_EntityBeanWrapper0.java:1558: ')' expected.
if (if(thread.contextContainer != null)
^
TimestampTest_EntityBeanWrapper0.java:1559: Invalid expression statement.
response != null) {if(thread.contextContainer != null)
         ^
TimestampTest_EntityBeanWrapper0.java:1559: ';' expected.
response != null) {if(thread.contextContainer != null)
                ^
TimestampTest_EntityBeanWrapper0.java:1560: Missing term.
response.setNanos(if(thread.contextContainer != null)
                  ^
TimestampTest_EntityBeanWrapper0.java:1560: ')' expected.
response.setNanos(if(thread.contextContainer != null)
                  ^
TimestampTest_EntityBeanWrapper0.java:1561: ';' expected.
response.getNanos());} // generated from BeanMethodCompilation
^
7 errors
Error compiling F:\oc4j\j2ee\home\applications\TimestampAppl/TimestampTestEntity.jar: Syntax error in source
Oracle9iAS (9.0.3.0.0) Containers for J2EE initialized

I need some helps about Web Services & Entity Bean

Hi everybody,
Using Jbuilder I can create Web Services object from Session Bean (with Weblogic 8.1).
I am wondering that: Can I create Web Service object from Entity Bean? Eg: with BMP or CMP?
If anyone knows how to do, please help me or give me the documents I can refer to!
Thanks in advance!

Hi everybody,
Using Jbuilder I can create Web Services object from Session Bean (with Weblogic 8.1).
I am wondering that: Can I create Web Service object from Entity Bean? Eg: with BMP or CMP?
If anyone knows how to do, please help me or give me the documents I can refer to!
Thanks in advance!

Error While Deploying A CMP Entity Bean With A Composite Primary Key

Hello all,
I have a problem deploying CMP Entity beans with composite primary keys. I have a CMP Entity Bean, which contains a composite primary key composed of two local stubs. If you know more about this please respond to my post on the EJB forum (subject: CMP Bean Local Stub as a Field of a Primary Key Class).
In the mean time, can you please tell me what following error message means and how to resolve it? From what I understand it might be a problem with Sun ONE AS 7, but I would like to make sure it's not me doing something wrong.
[05/Jan/2005:12:49:03] WARNING ( 1896):      Validation error in bean CustomerSubscription: The type of non-static field customer of the key class
test.subscription.CustomerSubscriptionCMP_1530383317_JDOState$Oid must be primitive or must implement java.io.Serializable.
     Update the type of the key class field.
     Warning: All primary key columns in primary table CustomerSubscription of the bean corresponding to the generated class test.subscription.CustomerSubscriptionCMP_1530383317_JDOState must be mapped to key fields.
     Map the following primary key columns to key fields: CustomerSubscription.CustomerEmail,CustomerSubscription.SubscriptionType. If you already have fields mapped to these columns, verify that they are key fields.Is it enough that a primary key class be serializable or all fields have to implement Serializable or be a primitive?
Please let me know if you need more information to answer my question.
Thanks.
Nikola

Hi Nikola,
There are several problems with your CMP bean.
1. Fields of a Primary Key Class must be a subset of CMP fields, so yes, they must be either a primitive or a Serializable type.
2. Sun Application Server does not support Primary Key fields of an arbitrary Serializable type (i.e. those that will be stored
as BLOB in the database), but only primitives, Java wrappers, String, and Date/Time types.
Do you try to use stubs instead of relationships or for some other reason?
If it's the former - look at the CMR fields.
If it's the latter, I suggest to store these fields as regular CMP fields and use some other value as the PK. If you prefer that
the CMP container generates the PK values, use the Unknown
PrimaryKey feature.
Regards,
-marina

How do I create an Entity Bean with unknown primary keys

Hi,
Can a good folk help me.
I am mapping an entity bean to an oracle table for the purpose of logging . I do not need a primary key contraint on this table. How do I specify in my entity bean file descriptor not to use any field for primary key ...
I have done this so far...
in my ejb.xml file - I set....
<prim-key-class>java.lang.Object</prim-key-class>
and deleted ....
<primkey-field>...</primkey-field>
My table structure is .....
CREATE TABLE FAMS_REQUEST_LOG (
EDITEDBY VARCHAR2(20),
OLDTRANSDATE DATE,
REQUESTID VARCHAR2(30) NOT NULL,
OLDQTY NUMBER(20),
NEWQTY NUMBER(20),
NEWTRANSDATE DATE)
but I still get this error message on deploying...
[#|2006-03-01T14:30:29.250+0100|INFO|sun-appserver-pe8.1_02|javax.enterprise.system.tools.deployment|_ThreadID=19;|Total Deployment Time: 11000 msec, Total EJB Compiler Module Time: 0 msec, Portion spent EJB Compiling: 0%|#]
[#|2006-03-01T14:30:29.265+0100|SEVERE|sun-appserver-pe8.1_02|javax.enterprise.system.tools.deployment|_ThreadID=19;|Exception occured in J2EEC Phase
com.sun.enterprise.deployment.backend.IASDeploymentException: Fatal Error from EJB Compiler -- JDO74046: JDOCodeGenerator: Caught a MappingConversionException loading or creating mapping model for application 'fixassetenterpriseapp' module 'FixAssetEnterpriseApp-EJBModule': JDO71030: There is no column in table FAMS_REQUEST_LOG which can be used to support the servers implementation of unknown key classes.
at com.sun.ejb.codegen.CmpCompiler.compile(CmpCompiler.java:274)
at com.sun.ejb.codegen.IASEJBC.doCompile(IASEJBC.java:615)
at com.sun.ejb.codegen.IASEJBC.ejbc(IASEJBC.java:563)
at com.sun.enterprise.deployment.backend.EJBCompiler.preDeployApp(EJBCompiler.java:340)
at com.sun.enterprise.deployment.backend.EJBCompiler.compile(EJBCompiler.java:209)
at com.sun.enterprise.deployment.backend.AppDeployer.runEJBC(AppDeployer.java:284)
at com.sun.enterprise.deployment.backend.AppDeployer.deploy(AppDeployer.java:176)
at com.sun.enterprise.deployment.backend.AppDeployer.doRequestFinish(AppDeployer.java:107)
at com.sun.enterprise.deployment.phasing.J2EECPhase.runPhase(J2EECPhase.java:146)
at com.sun.enterprise.deployment.phasing.DeploymentPhase.executePhase(DeploymentPhase.java:71)
at com.sun.enterprise.deployment.phasing.PEDeploymentService.executePhases(PEDeploymentService.java:633)
at com.sun.enterprise.deployment.phasing.PEDeploymentService.deploy(PEDeploymentService.java:188)
at com.sun.enterprise.deployment.phasing.PEDeploymentService.deploy(PEDeploymentService.java:520)
at com.sun.enterprise.management.deploy.DeployThread.deploy(DeployThread.java:143)
at com.sun.enterprise.management.deploy.DeployThread.run(DeployThread.java:172)
|#]
Dotun

you will have to create a sequence and a trigger
CREATE SEQUENCE <SEQUENCE NAME>
INCREMENT BY 1
START WITH 1
NOCACHE
/this sequence will guarantee that each requested number is unique
the trigger will select from this sequence and insert the obtained value in the new record
CREATE OR REPLACE TRIGGER <TRIGGER NAME>
BEFORE INSERT ON <TABLE NAME>
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
    BEGIN
        select
            <SEQUENCE NAME>.nextval
        into
            :NEW.<COLUMN NAME>
        from
            dual;
    END;
[/CODE]
this will always take the value from the sequence, even if you already provided a value yourself
(otherwise you will first have to test if :NEW.<column name> is null, but I wouldn't do this for a key column.
if you need the generated key back for further processing (inserting it into a child table for example), you can use the returning clause on the insert statement
see the oracle documentation for more information about sequences, triggers and the returning clause
greetings
Freek D
I am new to Oracle and need to know how to create a table that uses an automatic incrementation on a primay key for it's default. I need the uniqueness automatically managed by the DBMS.. This activity is know as setting the Column (primary key with identity) in Ms-SQL..
Your help would be appreciated greatly....
Thanks....

Report with entity beans - BIG performance problem

I have several EJBs (CMP entity beans).
I need to build a report using linked EJBs and show this report
to a user (so, updates are not needed - report is only for web page demonstration).
the problem is: such report is generated too slow.
I have ~100 records in table 'TestResult' and ~500 records in table 'TestObject'.
these tables are linked like this:
one testobject <--> many testresults
for each testresult I need to show a line with some info which should be retrieved
from bound EJBs (e.g. testresult-testobject-assigneduser-prioritylevel)
how to optimize such report generation?
I have heard something about session beans with Value Objects.
do I need to use such session beans here?
what is a general solution for generating reports using linked EJBs?
I tried to solve the problem by using DB View, but it didn't help.
I have used 'TestResultView' - info is retrieved fast enough from this view
(several msecs), but displaying this info is still very costly.
please, help!
Oracle 8.1.7,
WebLogic 6.1

Hi,
because I have checked the time required to
1) retrieve EJBS (several msec)Let me share some of my views with you.Once you retrieve the EJBS ie ie the collection of remote interface from the finder method the container is firing single "select " query and gets all the primary keys back.
2) cycle through it - get fields and display them
(~4000 msec)Now the cycle of getting the value you are getting the bean from the PooledState to ready state which will get the fields by firing the "select" query (ejbload()). Now in the instance you are invoking the multiple methods and at the end it will remain there in ready till you call the remove which u are not doing so the time out will bring it back to the pooledstate.
And if you are calling the bean very frequently then all the instances will go to the ready state and the activation & passivation will start developing ......
So at the end when the bean moves back to the pooled state after timeout the ejbStore() fires the "update " query!!!!
Let us consider the activation/passivation not appearing for simple understanding !!!!!!!!
So for each iteration you are firing 2 queries to the database.So if you have 500 records then the queries generatted will be 1(select from finder)+2(1 by select(ejbload)+1 by update(ejbStore))*500. So the flow is calling 1001 queries ...Thus quering about 1000 queries will definetly take some time...
So what is the solution????
Any way you dont require to fire the update query as you are just viewing the data...So u can stop calling the ejbStore().
Hence you queries will drop to half.Now how we can do this is by using the BMP.....
The other solution is using the Sessionbean and store the data all 500 records in the Object which can be called across the n/w. This object should implements the Serializable interface and this tech is the Transfer Object feature.....
Hope you find this useful..
regards
Vicky

About entity bean

Similar Messages

Maybe you are looking for