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From Sylvain Wallez <>
Subject [RT] error-handling for "cocoon:" pipelines
Date Thu, 10 Apr 2003 15:09:49 GMT

Currently <map:handle-errors> in a sitemap is ignored for internal (i.e. 
"cocoon:") requests. However, this behaviour is somehow limiting and 
Jürgen Seitz and Björn Lütkemeier (guess it's the correct lastname) have 
expressed the need to have additional control on this.

They gave only some abstract examples, but a concrete use case for this 
is coplets : they are included through a "cocoon:" URI, and, despite of 
that, it would be good if a coplet was able to produce a nice error 
result instead of just propagating the exception to the upper-level 
pipeline (the one that builds the portal page).

There are two ways to consider this problem.

1/ Error handling is controlled by the called pipeline
The contract of a pipeline may include the fact that it produces some 
fallback content in case of error. In that case, the current behaviour 
that ignores error handlers for internal requests is not good and we 
need a way to specify it. This can go through a new "when" attribute on 
<map:handle-errors> with the possible values "external", "internal", 
"always", the default being "external" since it's the current behaviour.

2/ Error handling is controlled by the caller
We can also consider that the caller knows what to do in case of failure 
of the called pipeline, and then want to control this externally. Two 
ways are envisioned for this :
2a/ Through the URI, using a new subprotocol : 
"cocoon:handle-errors/blah". There's a potential conflict here with the 
"cocoon:raw" protocol
2b/ Through a reserved request parameter : 
"cocoon:/blah?cocoon-handle-errors=true". Care must be taken to forbid 
this parameter for external requests to avoid security holes.

I'm personally in favor of 1/ and do not know about 2/ : is it good for 
error handling to be controlled externally ? 1/ and 2/ can also be both 
allowed and priority given to the external setting. FS ?

Thoughts ?


Sylvain Wallez                                  Anyware Technologies 
{ XML, Java, Cocoon, OpenSource }*{ Training, Consulting, Projects }

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