Using a backing bean in JDeveloper to assign bean class variables

Question

I am using JDeveloper 10 to make a jsp page that is a form full of inputs and buttons. JDeveloper then creates the setters and getters for you for the ids of the various inputs and buttons. I also have used JDeveloper to create a backing bean.
The idea of this is to have the backing bean read in parameter(s) from an http source/link(when the form is loaded or instantiated) and assign those parameter(s) to one of the bean class local variables.
The reason i want to do this is, is that when the form is loaded the first thing it will do is open up an available database(in the bean class constructor), then in the constructor call a function to do a database query that will return a result set that will then be used to fill up the form.
That variable that is assigned by the backing bean will be the value of a unique database identifier for doing the sql query so that is why it is important that i get this value as the form loads.
So simply i need to find out from someone how to do this. i am totally new to doing any jsp development or using managed beans and i have gotten far enough to launch the form, retrieve and write to the database using sql queries and all the rest.
I just dont know enough about managed beans to make a decision on things like making the bean have a session scope. do i need request scope? if i change to request scope how do i make sure the database isn't being called every time the page changes or is refreshed?(when i had it as request scope the constructor was being called every time the page was reloaded and that isnt effecient at all, especially with multiple users). can you define more than one managed bean in one faces config file? do i have to manually change something in the jsp file to make sure things run smoothly?
Just maybe things are easier than i see them to be and my only problem is that i just dont understand what i am doing. here is what my backing bean looks like now with just basic session scope.
An example of course would be something like: http://host:port/context-root/faces/register.jsp?12345 - where 12345 would be the value that i would like to assign to a local variable in my bean class that can then be used for filtering out information via a query then filling up the form, all this happening at instantiation.
<?xml version="1.0" encoding="windows-1252"?>
<!DOCTYPE faces-config PUBLIC
"-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN"
"http://java.sun.com/dtd/web-facesconfig_1_1.dtd">
<faces-config xmlns="http://java.sun.com/JSF/Configuration">
<managed-bean>
<managed-bean-name>beanpackage</managed-bean-name>
<managed-bean-class>beanpackage.beanclass</managed-bean-class>
<managed-bean-scope>session</managed-bean-scope>
<!--oracle-jdev-comment:managed-bean-jsp-link:1register.jsp-->
</managed-bean>
</faces-config>
This is what i have now, i've tried tons of stuff on the web like assigned value parameters but just am stuck on exactly what to do as nothing has seemed to work. Any help would be appreciated. Thanks in advance!

Answer 1

Hi,
don't think you will get a readily programmed solution to this (though I wish you luck). Here's how I would approach the managed bean issue
- One managed bean that you configure from a java.util.HashMap. This bean should be in requestScope (should be okay here). Say the bean is called "formFields", then adding data to it can be done with the following EL #{formBean['attribute_name']}. You need to add this as the value Expression of the inputText field you create dynamically. The filed will then read and write to the HashMap
- Create a managed bean in session scope to handle the database interaction. Put this into session scope (e.g. "database")
- Create a managed bean that holds the action listener that handles the update, insert and delete actions (e.g. logic handler). This bean has a JSF reference to the root component in the page (or the form layout component to add the fields to)
The "database" bean is referenced from the logic handler managed bean using the #{database} expression, which you resolve using a ValueBinding (ExpressionBinding in JSF 1.2). Or, you configure the bean as a managed property.
The logic managed bean also needs to reference the formFields bean (similar to above) to access the contained filed names and attributes. If the filed attributes match column names in the database then you should be all set
Frank