balagor

 Profile Answers by balagor 

• Nov 7th, 2005

 

answer

Ramarao A.V.

• Nov 8th, 2005

 

EJBQL is implemented using the XML file "ejb-jar.xml" file. We will use certain tags in the "EJB-Jar" file to implement EJBQL. 

SELVI

• Nov 19th, 2005

 

SUPERB!

vemodharak

 Profile Answers by vemodharak Questions by vemodharak

• Jan 11th, 2006

 

EJBQL is query language for CMP.It is vendor indipendent .In conainer managed persistency container is responsible for maintaining connecting to the database and accessing data. so the container has required to one query language toa access the data and give it to the bean class of CMP.Before the EJBQL we have another query languge for each and every application server.suppose weblogic server has welogic ql.problem with this it is purely vendor dependent language .so this purpose EJBQL is arised.It is working to each and every app server.problem with EJBQL ::::---------------------------------it working only for simple queries.and it having SELECT,FROM,WHERE clauses only.we can use those only.And EJBQL is used only in the SELECT methods and EJBFindByXXX() methods only

Lisa Richardson

• Jun 26th, 2006

 

Hi,

I've noticed that at the end of some assistant job title they would place CMP.

If they are already an executive assistant, why add - CMP?

Regards,

Lisa

Suresh

• Jul 7th, 2006

 

CMP means ContainerManagementPersistence. In this container will take care all database related things.

Manivannan Palanichamy

• Aug 23rd, 2006

 

Hi,

See my answers below:

>1. How EjbQL ara impemented when it is necessary?

EjbQL is defined by ejb spec. The container actually uses these queries in place of the method calls like findByXXX(), selectXXX () and etc.

When you use CMP, it is necessary to use EJB QL.

>2.what do you mean by shared transactional state data maintained by EJB?

Are you talking about JTA? Or container managed transaction?

>3.what do you mean by CMP & BMP &what is besic ifference between them?

BMP: Bean Managed Persistence; the bean developer has the responsibility to implement the database code and bean persistene management, life cycle code.

CMP: The container takes care of bean's persistence state management, transaction management.

Difference: As said above.

Also, incase of CMP, you specify the database info, field to entity instance maping, transaction condition in Deployment Descriptor. You have to manually write code for these things in case of BMP.

>4.where are databese maneged by Entity bean is implemented & how many instance of the Entity bean
for each client is maintained by Ejb container?please describe ths question conceptually?

Assume, a single entity bean refers to a single row in a table. In fact, thats what happens actually. When a bean is created, the container associates(stores) the corresponding row in the entity bean.

There is a single entity bean for a single row, independent of how many cleints access them.

5.whuy BMP class returns null & why CMP implementation class reurns instanceof PK class?

Can you make the question bit clearer? Anyway, a CMP requires the associated table to have a primary.

6.what do you mean by EJB client & EJB Server ?

Simple :-), EJB server is where the EJBs live; where their life cycles  managed.

EJB clients are those (a servlet/a jsp/a standalone java/a corba client/another ejb/a spring -- yes, its possible! ) who access the EJBS living in the server.

>7.where home interface resides?
remote mechine or client machine?

remote machine; I mean in the same heap, wherever the EJB resides.

8.How ejb,jsp,Oracle communicates in building a business Application

To answer in one single line,

JSP -> ejb -> Oracle