Exception handling OR How to abort XSP processing?

[Götz Botterweck <bo...@iwi.uni-koblenz.de>]

I'd like check some preconditions when running a XSP script.

For example something like this

	<xsp:logic>
		if( request.getParameter("formMode") == null ) {
			// output error message  "Required parameter
'formMode' was not provided."
			// abort
		}
	...
	</xsp:logic>

Is there some nice way to do this?

Thanks
Goetz

Re: Exception handling OR How to abort XSP processing?

[Ricardo Rocha <ri...@apache.org>]

On Tue, 09 May 2000, G�tz Botterweck wrote:
> I'd like check some preconditions when running a XSP script.
> For example something like this
> 	<xsp:logic>
> 		if( request.getParameter("formMode") == null ) {
> 			// output error message  "Required parameter
> 'formMode' was not provided."
> 			// abort
> 		}
> 	...
> 	</xsp:logic>
> Is there some nice way to do this?

I see 2 ways to achieve this:

1) You may subject all markup generation to this particular condition
    and return at the appropriate point if it's not met:

     <xsp:page ...>
        . . .
        <page>
          <xsp:logic>
            if (request.getParameter("formMode") == null) {
              <title>Required Parameter Missing</title>
              <p>
                <font color="red">
                   Required parameter "formMode" is missing, you moron!
                </font>
              </p>
              return;
            }
          </xsp:logic>

          <title>Normal Title</title>
          <!-- Normal Stuff -->
           . . .
        </page>
     </xsp:page>

2) You may redirect your request to an appropriate error page and
     return:

     <xsp:page ...>
        . . .
        <page>
          <xsp:logic>
            if (request.getParameter("formMode") == null) {
              response.sendRedirect(
                "error-page.xml?message=" +
                URLEncoder.encode(
                     "Required parameter 'formMode' is missing, you moron!"
                 )
              );
              return;
            }
          </xsp:logic>

          <title>Normal Title</title>
          <!-- Normal Stuff -->
           . . .
        </page>
     </xsp:page>