Simon, Thanks for your help understanding this - I will try placing my data access object in the application scope and the backing bean in a request scope. However, I'll need to use the t:saveState with the backing bean since I have a datamodel with a datascroller (as you had recommended in a previous post.) My application needs to be very scaleable, so I appreciate the design information.
Tom -----Original Message----- From: Simon Kitching [mailto:[EMAIL PROTECTED] Sent: Tuesday, January 17, 2006 9:14 PM To: MyFaces Discussion Subject: Re: Pattern for shared data access object? On Tue, 2006-01-17 at 21:00 -0500, Tom Butler wrote: > Where I need help understanding is how to set up the scope for the > managed beans and data access object. Currently, I have the backing > bean within the session scope (using the facesconfig.xml file). My > main question is how to set up the scope for the Data Access Object - > currently I do not have it as a managed bean within facesconfig.xml. > Instead I am creating a new instance within the backing bean: > > > > private DbInsert dbinsert = new DbInsert(); > > > > Is this the best way to do this? Will the DBInsert object now be tied > to the session scope of the backing bean (i.e., when backing bean is > deleted, the DbInsert object will be deleted from session scope as > well.) The bean is of session scope, so it will continue to exist until the user's session is deleted, or the backing bean is explicitly removed from the session. And of course the reference to the DbInsert object will live for the same time. > > > Ideally I would like the data access object to be available as a > shared object throughout the life of the application. When I was > programming using a servlet approach, I would have created a servlet > to load on startup. Now that I'm using java server faces, I'm > confused about the scope / how to efficiently set up a data access > object that I want to be available to all backing beans in the > application. > tnanks for any help understanding this. I would strongly recommend you avoid using session scope for backing beans (ie beans that provide presentation logic to a specific page). The bean is only relevant when the user is accessing certain pages, but will continue to exist until the user's session times out. Unless your app is just a few pages that's not a good idea. I recommend you put your DB access functionality in a bean that is declared as a managed bean of application scope. You can then declare your backing beans as request scope, and use a managed-property declaration to connect the backing beans to the Db access bean. <managed-bean> <managed-bean-class>example.DBInserter</managed-bean-class> <managed-bean-name>dbInserter</managed-bean-name> <scope>application</scope> </managed-bean> <managed-bean> <managed-bean-class>example.SomeBackingBean</managed-bean-class> <managed-bean-name>bean1</managed-bean-name> <scope>request</scope> <managed-property> <name>inserter</inserter> <value>#{dbInserter}</value> </managed-property> </managed-bean> Managed bean objects are created only when they are actually needed, so the dbInserter object will be created when the first page that references it (directly or indirectly) is viewed. If this is not desirable, and you prefer it to be created on webapp startup then you could use a ServletContextListener to create it. This page might be useful: http://wiki.apache.org/myfaces/AccessingOneManagedBeanFromAnother Regards, Simon
