Using request.setAttribute in a JSP page

Question

Is it possible to use request.setAttribute on a JSP page and then on HTML Submit get the same request attribute in the Servlet?

Alkmaar

Answer 1

No. Unfortunately the Request object is only available until the page finishes loading - once it's complete, you'll lose all values in it unless they've been stored somewhere.

If you want to persist attributes through requests you need to either:

1. Have a hidden input in your form, such as <input type="hidden" name="myhiddenvalue" value="<%= request.getParameter("value") %>" />. This will then be available in the servlet as a request parameter.
2. Put it in the session (see request.getSession() - in a JSP this is available as simply session)

I recommend using the Session as it's easier to manage.

Refractometer

Maybe that is not unfortunate. JSP scriptlets are a bad practice. Be careful when using the session, it is easier to manage but sometimes it is "expensive" in terms of scalability. – Hesperides

well, put it this way - the session is probably better than anything you write yourself :) If you're on a decent app server it can do replication etc, and you have options for storage (not just in memory). – Refractometer

Answer 2

The reply by Phil Sacre was correct however the session shouldn't be used just for the hell of it. You should only use this for values which really need to live for the lifetime of the session, such as a user login. It's common to see people overuse the session and run into more issues, especially when dealing with a collection or when users return to a page they previously visited only to find they have values still remaining from a previous visit. A smart program minimizes the scope of variables as much as possible, a bad one uses session too much.

Rotenone

Answer 3

If you want your requests to persists try this:

example: on your JSP or servlet page

request.getSession().setAttribute("SUBFAMILY", subFam);

and on any receiving page use the below lines to retrieve your session and data:

SubFamily subFam = (SubFamily)request.getSession().getAttribute("SUBFAMILY");

Klecka

This will access session attributes, not request attributes as was asked for. – Diaspora

Answer 4

You can do it using pageContext attributes, though:

In the JSP:

<form action="Enter.do">
    <button type="SUBMIT" id="btnSubmit" name="btnSubmit">SUBMIT</button>
</form>
<% String s="opportunity";
pageContext.setAttribute("opp", s, PageContext.APPLICATION_SCOPE); %>

In the Servlet (linked to the "Enter.do" url-pattern):

String s=(String) request.getServletContext().getAttribute("opp");

There are other scopes besides APPLICATION_SCOPE like SESSION_SCOPE. APPLICATION_SCOPE is used for ServletContext attributes.

Haygood

Answer 5

Try

request.getSession().setAttribute("SUBFAMILY", subFam);
request.getSession().getAttribute("SUBFAMILY");

Tipperary

This will access session attributes, not request attributes. – Diaspora

Answer 6

Correct me if wrong...I think request does persist between consecutive pages..

Think you traverse from page 1--> page 2-->page 3.

You have some value set in the request object using setAttribute from page 1, which you retrieve in page 2 using getAttribute,then if you try setting something again in same request object to retrieve it in page 3 then it fails giving you null value as "the request that created the JSP, and the request that gets generated when the JSP is submitted are completely different requests and any attributes placed on the first one will not be available on the second".

I mean something like this in page 2 fails:

Where as the same thing has worked in case of page 1 like:

So I think I would need to proceed with either of the two options suggested by Phill.

Alkmaar

Answer 7

i think phil is right request option is available till the page load. so if we want to sent value to another page we want to set the in the hidden tag or in side the session if you just need the value only on another page and not more than that then hidden tags are best option if you need that value on more than one page at that time session is the better option than hidden tags.

Aesthetics

won't the hidden tags trigger security issues if something we are sending is valuable. – Schick