wlappc ANT task

I've got a little problem with the ANT task applc witch interfaces Weblogic compilator.
This task is generaly used to :
- validate deployment descriptors at applicative level as well as in each module of the application.
- generate the classes of the application and check the jsp's syntax.

In fact, we would like to execute this task only when needed (if the deployment descriptor or a jsp has changed for example).
It seems that the 'forcegeneration' option of the wlappc Ant task can do the job (the doc is below).

forceGeneration :
Forces generation of EJB and JSP classes. Without this flag, the classes will not be regenerated unless a checksum indicates that it is necessary.

So I wrote :
<wlappc source="${dist}/${application}.ear" verbose="true" forcegeneration="false">
but I had the same result :
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appc:
[wlappc] [appc] Created working directory: d:\DOCUME~1\dsiv0636\LOCALS~1\Temp\appcgen

[wlappc] [appc] Compiling EAR module 'sea'
[wlappc] [JspcInvoker]Checking web app for compliance.
[wlappc] <29 sept. 2005 11 h 51 CEST> <Info> <HTTP> <BEA-101047> <[ComplianceChecker] Validating the servlet element with servlet-name named "InitConfig".>
[wlappc] <29 sept. 2005 11 h 51 CEST> <Info> <HTTP> <BEA-101047> <[ComplianceChecker] Validating the servlet element with servlet-name named "ConnecteurODIR".>
[wlappc] <29 sept. 2005 11 h 51 CEST> <Info> <HTTP> <BEA-101047> <[ComplianceChecker] Checking servlet-mapping for servlet name : "ConnecteurODIR".>
[wlappc] [jspc] parsing /statut.jsp:
[wlappc] [jspc] parsed d:\DOCUME~1\dsiv0636\LOCALS~1\Temp\appcgen\sea\statut.jsp in 704 ms.
[wlappc] [jspc] generated java file d:\DOCUME~1\dsiv0636\LOCALS~1\Temp\appcgen\sea\WEB-INF\classes\jsp_servlet\__statut.java
[wlappc] [jspc] Invoking the compiler

[wlappc] [appc] Validating EAR file.
[wlappc] [appc] Compilation completed successfully.
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The jsp witch hasn't changed has been checked and generated.

Would you have any idea of what's happening ?