Ramakrishna Allam

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Recent posts by Ramakrishna Allam

Thanks everybody .
16 years ago
Guys ,
I am happy to share my experiences with you . I just scored SCBCD with 98%. One question went wrong . Thats a drag and drop question . The thing is it didnt allow me to answer . When I am trying to drang it , it was giving some script error . I complained to the prometric centre guys . They couldnt help me . Otherwise , I would have got 100%. But still I am heppy.

If youy are looking for some preparatory books , its none other than HFEJB . Pnly with this book u can score 90%+ . But u should understand in and out of it . Ofcourse , I studied EJB spec also . revised the theoritical concepts like EJB env , security , responsibilities of different roles , EJB QL and Entity beans chapter . It was tough going thru that. I studied Mikalai Zaikin's SCBCD Guide .I went through only the theoritical chapters that I mentioned above . Thats a good notes . Otherthan that , as everytime it is proved , mock exams is a muct . I gave it on ejbcertificate.com , jdiscuss mocks . The real exam is a bit easier than ejbcertificate.com . And also this forum is of great use .

In the end , Many many thanks to Kathy for a such a nice funny book .
16 years ago
instead of using collections and adding it specifically , if u use set methods of the bean , no need to remove them specifically . Container takes care of it.
You are right . U need to have a specific code to remove it through Iterator.remove() . otherwis e, u will see a IllegalStateException
Infcat what he says on the page 135 of the spec is ,

If elements are added or removed from the underlying
container-managed collection used by an iterator other than by the java.util.Iterator.remove() method, the container should throw the
java.lang.IllegalStateException on the next operation on the iterator
Collection nySalesreps = nyOffice.getSalesreps();
Collection sfSalesreps = sfOffice.getSalesreps();
Iterator i = nySalesreps.iterator();
Salesrep salesrep;
// a wrong way to transfer the salesrep
while (i.hasNext()) {
salesrep = (Salesrep)i.next();
sfSalesreps.add(salesrep); // removes salesrep from nyOffice
}
// this is a correct and safe way to transfer the salesrep
while (i.hasNext()) {
salesrep = (Salesrep)i.next();
i.remove();
sfSalesreps.add(salesrep);
}


The first comment is beacuse of the referential integrity . But doing that way , will throw an IllegalStateException . We should do the second way .
I think the same can be achieved using the following query
SELECT OBJECT(p) FROM Order o , IN(o.lineItems) l , Product p
Even that looks wrong . As the spec on page232 says that,"The SELECT clause must not use the OBJECT operator to qualify path expressions."
So ,
---------------
select Object(l.product) from Order o , IN (o.lineItems) l
-----------------
is also not valid . So , Its true that Kathys book is right . On page 406 , she says that select clause cant be used to return CMR fields.(because CMRfiled is an entity bean by itself , u have to use Object to return that . and the page 232 of the spec says that slect clause must not use OBJECT operator to qualify path expressions .ie since ,l.product is a path expression , we cant use OBJECT to qualify that for select clause).
Any thing went wrong in my explonation ?
Looks like , though EJB-QL is a small chapter and concept , there are around 5 questions in the exam . So , better prepare well for that and put more questions on the forum .
Ramakrishna R Allam ,
SCJP-95% , SCWCD-96%
Hi Cyril,
It doesnt look like product, in the following query is a CMR field .
----------------------
SELECT l.product FROM Order AS o, IN(o.lineItems) l
------------------
Though the spec says that product is a CMR field on page 221 , in the example it doesnt look like one. As far as my understanding goes , if u return a beans component interface or a collection of such in the ejbSelect methods , u should have used Object as follows.
------------
SELECT Object(l.product) FROM Order AS o, IN(o.lineItems) l
----------------
please guys , correct me if iam wrong .
I havent gone thru ur code fully . But , page 494 of the spec says that "An enterprise Bean must not use the AWT functionality to attempt to output information to a display, or to input information from a keyboard."
Hi Constantino,
I got this doubt earlier and got clarified in this forum only . SO , I will be enlightening u this time , thanks to my great helping nature :-)(just kidding) . EJB spec on page 81 says that , "Accessing resource managers and enterprise beans is disallowed in the session bean methods for which the Container does not have a meaningful transaction context or client security context." . Observe the OR part as well , "client security context" . ejbCreate() , ejbRemove() , ejbActivate() and ejbPassivate() [4 methods] have client security conetxt though they do not have the transaction context.(that is the reason why we can call gerCallerPrincipa and isCallerInRole() in those methods) .So , we can access resource mgrs and other enterprise beans as well in those 4 methods. But only in case of SFSB . In case of SLSB , we have neither transaction context nor security context . So , we can not access resource mgrs and other beans .
If this is the case, i have got another doubt which hasnt been clarified . afterCompletion in CMT stateful method , though doesnt have transaction context , has a security conetext . But surprisingly, it doesnt have access to resource managers and other enterprise beans . If u understand why , please let me know.
Hi Chung,I think its true for irrespective of the statefull ness of the bean (its true for both stateful and stateless beans) .And , all the create methods in remote homes muct throw CreateException. Isnt it?
Thanks very much . Its a great point . I could not observe that . Looks like i need to see everything very clearly .
yeah....U are right.
Infact ejbCreate() , ejbRemove() of both SFSB , SLSB are not in transaction context. So , setRollbackOnly and getRollbackOnly()(for CMT beans) methods cann not be accessed (in both SFSb and SLSB). this is true for ejbActivate() and ejbPassivate() methods of SFSB .
But in all the cases , if the bean is a BMT one , its possible to call the getUserTransaction() method in all the methods .(I do not undertsand why!!.When there is no transaction context running , (infact) when an unspecified tranction context is running , will it be possible to call getUserTransaction[ofcourse in BMT]). If that is the case , EJB spec should be right for the above Q'n . i.e getUserTransaction can be called from stateless ejbCreate and ejbRemove . Somebody please explain . this is really confusing .
The relationsships are defined only in EJB spec 2.0 and not earlier .. And they are only for CMP . not for BMP . The the target of a relationship- should be a CMP and should define local interfaces (both home and remote , though it can define remote interfaces as well).
I think we can do both the ways as everybody know . But It might be more appropriate to do it in the setXXXContext() methods . I remember i read some where in the spec , that we will write code that required for the life time of the bean in setXXContext() methods . But I read that for entity beans . Should be same for session as well as MDB . Any comments?