Passing vectors into JSP from Servlet and passing data back to Servlet

Question

I have been building an MVC application.
It has a controller which instantiates classes and evokes methods to
populate vectors. These vectors are then passed into a JSP. This part of the application works fine.
What I am having trouble with is a new JSP I have designed; this will
display the data that is actioned by the FORM action. This is actioned
based on the Search criteria entered by the user. Based on this a further vector is populated and brought back to the JSP as a vector
and this is rendered via the TABLE tag. Again this works fine.
Against each of the rows displayed, I have a print checkbox which can be checked by the user. On checking the records they want to print, they should then hint a Print button which should go back to the Servlet and print the data. THIS IS WHERE I HAVE THE PROBLEM. On going
back to the servlet the checkbox values are not displayed, rather
the values that initially populate the JSP. How do I get these new values back into the vector and hence accessible from the Servlet.
Any help with be very much appreciated.
Chris

Answer 1

Thanks for this.
Just to clarify I am not using Struts.
What I am having difficulties with is the fact that:
I can't get the checked values back to the Servlet - they keep the values they have in the bean - so as part of instantiating the bean class I set the value of the item to 'off'. The user will then check
the checkbox which should presumbably set the value to 'on'. This isn't happening because the setter method of the bean is not evoked again
because I don't come into this JSP again - the Servlet has finished here
and now needs to print the records. It can't do this because as
far as it is concerned nothing has changed since it last passed through
the vector to the JSP.
Even when I do the following:
Enumeration paramNames = request.getParameterNames();
String param = null;
while (paramNames.hasMoreElements())
param=(String)paramNames.nextElement();
System.out.println("parameter " + param + " is " +
request.getParameter(param));
what comes back is the valus of 'off' as opposed to 'on'.
The other thing is that 'request.getParameterNames()' only works
with the first record in the vector, i.e. it doesn't fetch any other
records that are rendered in the <TABLE> tag.
In desperation is there anybody out there who can help me.
Thanks
Chris
I am going to assume you are using a MVC framework
like Struts or very similar (I am assuming that from
the language you are using).
When the servlet passes the vector back to the JSP
page and you render the HTML that is passed back the
client your Vector is gone. The Vector is not
available at the HTML level that is being viewed at
the browser.
When the user selects the checkboxes and submits the
page (by clicking the print button) the controller
servlet (called ActionServlet in Struts, yours maybe
called something else) forwards the request to the
appropriate JavaBean and Servlet to process the
request. Either the JavaBean has to recreate the
Vector (not recommended) or the processing Servlet can
(better). You can do this by recreating the Vector
from scratch for the HttpRequest parameters or, at the
time of the initial request, saving Vector to a
session and then updating with the data you get back
from the client (again from the HttpRequest
parameters).
Either way you have to work with
HttpRequest.getParameter().