Suggestions/Comments inline.
-Tim
-----Original Message-----
From: Jay Burgess [mailto:[EMAIL PROTECTED]]
Sent: Thursday, April 25, 2002 10:22 AM
To: [EMAIL PROTECTED]
Subject: Model 2 questions
(I got no replies on the JSP list to these questions, so I thought I'd try
here...)
In the Model 2 architecture:
(1) Is there a difference between having the controller servlet store the
"model" beans in the Request or the Session before forwarding to the JSP?
Is one better than the other, or preferred from some reason?
>>>
The request object "dies" after it receives a response from a page.
Therefore, it really depends on what you need the bean for. For example: if
I have a bean that is being used to display a snapshot stat of something
(like box scores etc) I might only want this bean to be used one time in
that page. And after it is displayed.. I dont need it again (why keep it if
they dont want to see the scores anymore). Therefore, just put it into the
request. But if I have a shopping cart and that is represented by a bean.
Then I want to keep that around not just for the page that shows it.. but
for any page that uses it.
Therefore, I would want to put it into the session scope. This keeps it
around for future use AND associates it with a particular client.
A good rule of thumb would be... if more than one page for a particular
client uses the bean.. store it into session scope.. if more than one page
for ALL clients use the SAME bean and information in the bean then store it
into application scope.. else page scope (request) will be sufficient.
>>>
(2) How am I supposed to handle the case where the bean(s) that the
controller servlet is supposed to instantiate are determined by the tags
that are present in the requested JSP? Does the servlet have to open and
parse the JSP somehow in this case? As an example:
Assume I have 2 custom tags, one that displays the data from a database
table as an HTML table, and one that creates a .JPG chart image of table
data.
If Page1.jsp contains three tags ("show Table 1 as a chart", "show Table 1
as a table", and "show Table 2 as a table"), then I'd like to load Table 1
data into one bean, Table 2 data into a second bean, and then forward to
the JSP and let the custom tags do their drawing and charting with the two
beans. This is most efficient, as I'm only requesting data for Table 1
once, even though it's being used twice in the JSP.
But in this scenario, how can my controller servlet determine which
table(s) it needs to create beans for from the database?
>>>
The best way to do this is for another page to send a request to the
Servlet to tell it what is needed before the Servlet sends out to the
displaying JSP.
Another way to do it is for the displaying JSP to set up the bean
(using useBean). Of course if it needs to do some data
population/calculation.. this is not really the preferred approach.
>>>
Jay
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