RE: Database Connection in Logic Beans - pooling? => request cycle

[Frederic Laub <in...@012.net.il>]

I got the message and I will use the sessionFacade pattern and use the
connection pool as you advised.
Nevertheless I would like to know where the request cycle ends in the struts
framework?
I didn't find any diagram regarding the request cycle.
I would like to store (among other things) the time for processing each
request.
I suppose I'll have to put the code in the controller component, the
ActionServlet?
How can I best achieve this?

Thanks to you all for your advice.
Frederic

-----Original Message-----
From: David Graham [mailto:dgraham1980@hotmail.com]
Sent: Tuesday, September 03, 2002 6:35 AM
To: struts-user@jakarta.apache.org
Subject: RE: Database Connection in Logic Beans - pooling?


Do NOT save the request into the session.  That's why there is a connection
pool (DataSource), you take one out, use it, and put it back.  If you don't
return it you will ruin the whole point of the pool.  The connection pool
idea was created to avoid the situation you described.  You should always
ask the pool for a connection when you need one and put it back when
finished; your application's response time will greatly improve.

Dave

>Thanks to Troy,
>
>But I read a lot of Java literature and the struts archive over the past
>weeks but in the all the examples the connection is retrieved and returned
>is the same class. I know it is the easiest and the best way to handle the
>problem.
>In most cases it provides a solution.
>I would like to implement a more flexible solution:
>- Retrieving a connection and saving it in the context (request scope) or
>saving an id associated with the connection.
>- When a connection is needed in the request, look first in the context if
>a
>connection has already been retrieved.
>- Based on a parameter => return the connection in the class.
>- Check at the end of the request if a connection exists, if yes return it
>to the pool.
>=> Where does the request cycle ends?
>At the source I'm a database programmer so I prefer to manage the
>transactions myself.
>I think that another advantage of using a same connection through the whole
>request is the fact that in case of heavy loading, when connections are
>difficult to obtain, the request can be served as a whole. I prefer X
>requests with 100% satisfaction and y not satisfied than x+y requests with
>30% satisfaction. If you understand what I mean?
>
>Your help or advice will be appreciated.
>Frederic
>
>I've excluded EJB for my project because most of the data is read only or
>linked to one user only.
>
>-----Original Message-----
>From: Troy Hart [mailto:thart@part.net]
>Sent: Monday, September 02, 2002 9:17 PM
>To: Struts Users Mailing List
>Subject: RE: Database Connection in Logic Beans - pooling?
>
>
>You can solve this problem by providing a business service framework for
>your application (There has been a lot of talk about this sort of thing
>on this list...I can't think of a particular thread to reference for you
>so you may just want to go through the archives). My approach to this
>problem has been to create a set of very coarse grained business service
>components (ours is an ecommerce system so we have components like the
>following: one for cataloging, one for requisitioning, one for order
>services, and etc...), where each component provides a public API that
>mirrors the "use-cases" one-to-one (for the most part). I think you will
>find that the top level "use-cases" defined for your system provide
>natural scoping boundaries for your transactions, and resource
>management in general.
>
>This approach will leave you with a set of re-usable business components
>that are not tied to struts and/or the servlet paradigm. Also, this API
>provides an abstraction that will allow you to hide complexity from your
>struts actions (or whatever else uses the API). For example, the
>component you expose could be a facade to an EJB Session bean
>(http://java.sun.com/blueprints/corej2eepatterns/Patterns/SessionFacade.htm
l
>).
>
>Anyway, my suggestion is to think about your problem a little
>differently. Sorry if I didn't provide enough details, my intention was
>simply to give a high level overview of how I see the problem and the
>solution. Once again, I would urge to lookup other threads on this topic
>to read what other people have said.
>
>Hope this helps,
>
>Troy
>
>
>On Mon, 2002-09-02 at 10:45, Frederic Laub wrote:
> > Hi,
> >
> > How do achieve the following:
> > In some cases I want to get a connection at the beginning of a request
> > (request scope), pass the same connection to all the java beans that are
> > called in the request and return the connection at the end of the
>request.
> > Where do I put the code to return the connection to the pool at the end
>of
> > the request and in case of an error be sure that the connection is
>returned
> > to the pool?
> > A same connection is required when all DML statements throughout a
>request
> > are part of a same transaction.
> > The commit (or rollback in case of an error) statement is issued at the
>end
> > of the request before the connection is returned to the pool.
> > Sorry if the vocabulary I used is database oriented and not 100 %
> > java/struts compatible.
> >
> > Your help will be appreciated.
> > Frederic
> >
> >
> > -----Original Message-----
> > From: thart@part.net [mailto:thart@part.net]
> > Sent: Monday, September 02, 2002 9:06 AM
> > To: Struts Users Mailing List
> > Subject: Re: Database Connection in Logic Beans - pooling?
> >
> >
> > Steve McLeod writes:
> >
> > > I am using:
> > > Tomcat 4.0
> > > Struts 1.0.2
> > >
> > > The problem
> > > ========
> > >
> > > I have successfully used the Struts database connection pooling in a
>trial
> > > web app, but as far as I can tell, a reference to the datasource can
>only
> > be
> > > obtained from within an Action class (or directly within a JSP page
>but
> > > let's not think about that today).
> > >
> > > However I would like to have logic beans which handle database access,
> > > rather than have this in the Action class. But I can't get a reference
>to
> > > the datasource from the logic bean because it doesn't have a
> > ServletContext
> > > to which I can get a handle.
> > >
> > > I have toyed with various ideas:
> > > - Initialise a logic bean by passing it a reference to the Servlet
> > > - Acquire a connection in the Action class and pass that to the bean
> > >
> > > But really, I would rather the logic bean know inherently how to
>acquire
>a
> > > database connection.
> > >
> > > My current workaround is to not use the Struts connection pooling, and
> > > rather to manually create a connection each time database access needs
>to
> > be
> > > done, then destroy it. But this is clearly not suitable for our
>production
> > > environment.
> >
> > There are a few ways to solve your problem. One way would be to bind a
> > datasource to some JNDI name that your logic beans are aware of. Then,
>using
> > that name, your logic beans can lookup the datasource completely
>independent
> > of struts.
> >
> > Give it a try,
> >
> > Troy
> >
> > >
> > >
> > > The context of my problem
> > > ==================
> > >
> > > I want to use some code like this in a JSP:
> > >
> > > <jsp:useBean id="abean" scope="page"
> > > class="au.com.sunesis.timesheets.ClientManager" />
> > > <table border="1">
> > >     <tr>
> > >         <th>#</th>
> > >         <th>Client</th>
> > >         <th>Active</th>
> > >     </tr>
> > > <logic:iterate id="clientList" name="abean" property="clients"
> > > type="au.com.sunesis.timesheets.Client">
> > >     <tr>
> > >         <td><bean:write name="clientList" property="clientID"/></td>
> > >         <td><bean:write name="clientList" property="clientName"/></td>
> > >         <td><bean:write name="clientList" property="active"/></td>
> > >     </tr>
> > > </logic:iterate>
> > >
> > >
> > > The idea is that ClientManager is used to handle all general database
> > tasks
> > > for the Client bean (which maps to a Client entity in the database).
> > > ClientManager.getClients() connects to the database, creates an
>ArrayList
> > of
> > > Client objects, one for each row in the database, and returns the
> > ArrayList.
> > >
> > > ClientManager has other methods, such as:
> > > -         ClientManager.delete(Client c), which deletes the row in the
> > > database entity corresponding to the specified client.
> > > -         ClientManager.findByPrimaryKey(int ID) which returns the
>Client
> > > which matches the specified ID
> > > -         ClientManager.save(Client c), which stores the client in the
> > > database, creating or updating as necessary
> > >
> > > So an Action class can also call any of these directly, and it really
> > > shouldn't care about how these work and how they store to/retrieve
>from
> > the
> > > database. But I can't think of the elegant way to do this and still be
> > able
> > > to use the Struts connection pooling.
> > >
> > > Any thoughts?
> > >
> > > Thanks
> > >
> > > Steve McLeod
> > >
> > >
> > >
> >
> >
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