Oliver Kaljuvee wrote:
> Hi,
>
> Does anyone know how 'carry' the input values once a JSP is processed. For
> instance, if the user gave different passwords on the original form; once you
> process the form, you will notify the user that they have to provide a new
> password. However, you want that the user does not have to fill out every field
> again.
>
> Thanks.
>
> -- Oliver
I approach this kind of issue by using a bean that maintains the values. I prefer
the "put the logic in servlets and the presentation in JSP pages" approach to app
design -- I suppose you could do this with only JSP pages, but the separation makes
the structure clearer (at least to me). Here's an example of a login form that
does not require the user to type in both values if they make a mistake.
The same general approach can be used to maintain input values (from the user's
perspective) for *any* input form where you are doing server-side validation, and
might ask the user to fix something and submit again. I find it easiest to define
a bean that maintains all the fields for each particular input form.
(1) Login JSP Page (relevant excerpts only)
<jsp:useBean id="attemptBean" scope="request"
class="com.mycompany.AttemptBean" />
<div align=center>
<form action="http://www.mycompany.com/loginServlet">
<table border=0 width="100%">
<tr>
<th colspan=2>Please Log In</th>
</tr>
<tr>
<th align=right>Username:</th>
<td><input type="text" name="username"
value="<%= attemptBean.getUsername() %>"></td>
</tr>
<tr>
<th align=right>Password:</th>
<td><input type="password" name="password"
value="<%= attemptBean.getPassword() %>"></td>
</tr>
<tr>
<td colspan=2>
<input type="submit" value="Log In">
<input type="reset" value="Reset">
</td>
</tr>
</table>
</form>
</div>
(2) Login Servlet - basic logic flow:
Accepts the "username" and "password" parameters from the request.
Attempts to validate this username/password combination.
If valid, stash some stuff in the session and use a request dispatcher to forward
to the main menu JSP page.
If invalid:
Create an attempt bean with the values last submitted
Store this bean under key "attemptBean" in the current request
Use a request dispatcher to forward to the login JSP page.
(3) AttemptBean
The attempt bean has two String properties -- username and password. The only
trick is that if you set one of these values to null, it returns a zero-length
string instead.
Note that this bean gets created by the login JSP page if it's not already in the
request. The constructor initializes the values to zero-length strings, so that is
what you see the very first time you access the login JSP page.
In my real application, I also display an error message alert if you are returning
to the login page after an invalid attempt -- this was left out of the example
above for clarity.
Craig McClanahan
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