0002481: RequestDispatcher forward

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Category

Severity

Reproducibility

Date Submitted

Last Update

0002481

[Resin]

minor

always

03-03-08 09:17

06-11-08 13:36

Reporter

ferg

View Status

public

Assigned To

ferg

Priority

normal

Resolution

fixed

Status

closed

Product Version

3.1.5

Summary

0002481: RequestDispatcher forward

Description

(rep by Ilya Kasnacheev and Huitang Li)

This is an excellent finding. I got the same IllegalStateExceptions as
well when jsp:include a struts1 action with resin 3.1.4.

I tested with struts 1.0.x, 1.1.x, and 1.2.x, I got the same error.
However, when I tried struts 1.3.8, this exception disappeared.

I posted the similar question on the list several weeks ago, and I was
suggested to use the switch flush="false", which actually did not make
any difference.

If anyone knows the solution for avoiding this exception with struts
versions less than 1.3.x, please let me know.

Thanks.

Ilya Kasnacheev wrote:
I've found one thing in resin 3.1 regarding RequestDispatcher, include() and
forward()

Let's suppose we have a ServletResponse, and we've wrote some text into its
output stream, so it's now in "committed" state.
That means, as J2EE spec tells, that we can no longer do forward() on it, or
we'll get an IllegalStateException. In the meantime we can do include() on
it, including the response from random URI into result document.

So we include() a chain of struts1 actions into it.
They're going to forward() the request until the end of chain is reached.
As I've found out, this will result in a shower of IllegalStateExceptions
being thrown. Interesting thing that, despite those exceptions, actions
successfully transfer control from one to another, eventually finishing
processing and writing everything they need to.

Now the weird thing is:

On the first side, include()d document can be thought as being processed
independently. Basically it should behave as if you fetched that page by
using HTTP and then printed it into output stream. So, forward() should work
because there is no reason for it to not work - because it would work in the
case of outside request.
On the second side, include()d document gets unmodified ServletResponse from
parent servlet, which have its buffer committed, and I guess there are no
easy ways to tell whenever forward() was called from include()d servlet,
where it is fine, or from the parent servlet, where it's a no-no

I can't say I have a question about resin, I just wanted to share that bunch
of facts and thoughts with you.

P.S. Having said that, I find the original limitation on forward() rather
annoying. I guess it's supposed to ensure cookies and headers neither being
written into document nor discarded, and also prevent from outputting half of
one html document and then outputting the whole another html document.

That's the well known "We didn't want to let you shoot yourself in the foot so
we duct taped your fingers together; and also, we wanted to prematurely
optimise a bit" antipattern clearly.

Additional Information

Attached Files

Relationships

Notes
(0003173) ferg 06-11-08 13:36	server/10y5

Issue History
Date Modified	Username	Field	Change
03-03-08 09:17	ferg	New Issue
06-11-08 13:36	ferg	Note Added: 0003173
06-11-08 13:36	ferg	Assigned To	=> ferg
06-11-08 13:36	ferg	Status	new => closed
06-11-08 13:36	ferg	Resolution	open => fixed
06-11-08 13:36	ferg	Fixed in Version	=> 3.2.0

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