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Struts & Hibernate
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| | | Subject: DAO, Entity CMP, Strategy | Subject: DAO, Entity CMP, Strategy 2004-09-28 - By Manish Malhotra
Back
Hi,
In the code snippet of the DAO factory. The objects of DAO's are created
using SingleTon pattern.
But I have also doveloped the same factory and I asked the question that do
Is this the right design or it could create the bottelneck situation for the
application.
My application was getting hanged during stress testing. So, I raised this
question.
Now, can you explain that is there any flaw when our application is going to
be used by simoltaneously users.
Your input is appreciable.
Manish
-- --Original Message-- --
From: An interest list for Sun Java Center J2EE Pattern Catalog
[mailto:J2EEPATTERNS-INTEREST@(protected)]On Behalf Of Koala
Sent: Thursday, September 23, 2004 1:46 PM
To: J2EEPATTERNS-INTEREST@(protected)
Subject: Re: DAO, Entity CMP, Strategy
Ricardo de Souza Moura wrote:
> I wish I can to do all my database access by a DAO.
> But, what if I have a Entity CMP ? Would be a good pratice to use a
> Strategy
> pattern ?
>
> for sample:
>
> /*
> DAO Interface
> */
> public Interface CustomerDAO{
> public void insertCustomer(String name);
> }
>
> /*
> DAO implementation
> */
> public class CustomerDAOEJBImpl implements CustomerDAO{
> Context context;
> EJBHome home;
>
> public CustomerDAOEJBImpl(){
> context = InitiContext();
> home = context.lookup(...);
> }
>
> public void insertCustomer(String name){
> home.create(name);
> }
>
> }
>
> thanks in advance
>
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>
A good example is Firestorm a dao generator tool. Here how to do. For
each DAO MyDAO create:
1. a value object MyDAOValue
2. an interface
interface MyDAO {
PrimaryKey create(MyDAOValue v);
void remove(PrimaryKey p);
void update(PrimaryKey p ,MyDAOValue v);
...
Collection findAll();
MyDAOValue findByPrimaryKey(PrimaryKey p)
}
notice I use value objects for my CRUD methods.
2. An implementation class MyDAOImpl with two constructors:
class MyDAOImpl extends MyDAO {
MyDAOImpl() { } // if the dao do not
partecipate to an external transaction
MyDAOImpl(Transaction t) { } // if the dao partecipate to an
external transaction
....
}
3. A factory with the following methods:
class MyDAOFactory {
static MyDAO create() {
// here you can read from a conf file to understand what DAO create
if (dao == null)
dao = new MyDAOImpl()
else
return dao;
}
static MyDAO create(Transaction t) {
// here you can read from a conf file to understand what DAO create
return new MyDAOImpl(t)
}
private MyDAO dao;
}
This is the implementation provided by Firestorm (a dao generator tool).
With EJB there is a problem I explained in the thread CMP -DAO, please
see there.
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