Webdispatcher: Syntax error using modification handler

[Former Member]

Hello,

I have a problem with our webdispatcher (7.42 Patchlevel 224) on a SuSe Linux System. I want to use it for multiple systems by using the modification handler like in

Configuring SAP Web Dispatcher to Dispatch Requests to Different Systems - User Interface Add-On for...

wdisp/system_conflict_resolution = 1 is set and I defined a modification file:

icm/HTTP/mod_0 = PREFIX=/,FILE=/usr/sap/WDP/SYS/profile/modification_rule.txt

I want to modify the target sid depending on the URL. If the statement „o=SCM“ is in it, SCM should be set via SetHeader.

if %{PATH} regimatch *o=SCM*

SetHeader x-sap-webdisp-target-sid SCM [break]

When I enter this statement in modification_rule.txt the webdispatcher will not start.

FATAL: HttpModHandlerInit: Error processing rule file /usr/sap/WDP/SYS/profile/modification_rule.txt: syntax error in line 2: >if %{PATH} regimatch *o=SCM*     <. See SAP note 1918448.

The syntax error seems to be related to the asteriscs (*) because a statement like

if %{PATH} regimatch o=SCM

SetHeader x-sap-webdisp-target-sid SCM [break]

works, but is the wrong regular expression and can not be used for my purposes. What ist the problem with the asteriscs? I tried it with "*o=scm*" and '*o=SCM*'. The later does not give the syntax error but again its the wrong regular expression.

Any idea is welcome...

Thx.

  Best regards

   Harry 

[Former Member · Accepted solution]

Hi Chris,

thx for the hint. But I think the regular expression is correct. In principle it's like SAP proposes in the link that I mentioned. *bla* meaning "bla" somewhere in the phrase. But unfortunately it does not work this way. It's somehow like some kind of unwanted wildcard expansion of an asterisk in a shell.

c u

   Harry

[feng_shi · Accepted solution]

Hi Harry,

Please find below,  the meaning of *:

-------------------

The * (asterisk or star) matches when the preceding character occurs 0 or more times, for example, tre* will find tree (e is found 2 times) and tread (e is found 1 time) and trough (e is found 0 times).

-------------------

if you define *o=SCM*, since there is nothing in front of o=SCM, therefore, the syntax error occurs.

in this case, I think you should define modification rule file like below:

if %{PATH} regimatch .*o=SYS.*

SetHeader x-sap-webdisp-target-sid SCM [break]

if the statement o=SCM in it, then SCM will be set via SetHeader.

The . (period) means any character(s) in this position.

Best regards,

Shi Feng

[Former Member]

Hi,

thx for your answer. .*o=SYS.* works 🙂 And a simple o=SYS without any asterisk works too as I found out.

Did the behaviour of the webdispatcher concerning the regular expressions change at some release? Because I've seen the version with simple asterisks (like *bla*) in all SAP documents that I found.

Anyway. It works. Thx again 🙂

c u

  Harry

[feng_shi]

Hi Harry,

I don't think this is related to sap webdispatcher release because the regular expressions is the common and standard.

Maybe just a mistake of SAP online documents.

Anyway, Since it works, please mark this question as answered.

Thanks and best regards,

Shi Feng

[cris_hansen]

Hello Harry,

Please have a look at the regular expression syntax here.

Please also read about the new modification actions in SAP note 2042819.

Cheers,

Cris