Tuesday, January 05, 2016

DSAPI for Domino

This post is about to make short summary about DSAPI filter. I've finished my project some time ago and it looks like I'm not going to do any work with it in near future.

What is DSAPI?

The Domino Web Server Application Programming Interface (DSAPI) is a C API that lets you write your own extensions to the Domino Web Server. DSAPI extensions, or filters, are notified whenever a particular event occurs during the processing of a request.
I've written few articles about DSAPI before and now it is time to publish my work/project on github. You can find it here: domino-dsapi-handler. I did not have time to make a documentation for it (and I'm not sure I will do it, without funding), but all sources are there.

In this post I will highlight most important things you need to know if you are going to build your own DSAPI filter.


Domino calls the initialization function when the filter is loaded. The filter is loaded when the Domino HTTP server task is started or when the HTTP task is restarted with the Domino console command 'tell http restart'.
 DLLEXPORT unsigned int FilterInit(FilterInitData* filterInitData) {  
  // init events you want to handle  
  filterInitData->eventFlags = kFilterRewriteURL | kFilterResponse | kFilterTranslateRequest;  
  // another code  
  return kFilterHandledRequest;  
 } // end FilterInit  

Terminate filter

The filter may also define a termination entry point. Domino will call this function whenever the filter is about to be unloaded. The filter can use this function to clean up resources it allocated
 DLLEXPORT unsigned int TerminateFilter(unsigned int reserved) {  
  return kFilterHandledEvent;  
 }     // end TerminateFilter  


The Event Notification function does the actual work of the filter. Domino calls the Event Notification function whenever a particular event occurs during the processing of an http request. When Domino calls the filter's Event Notification function it passes information about the request and the event being processed. On each call the filter can decide to handle the event, with or without an error return, or decline to handle the event.
 DLLEXPORT unsigned int HttpFilterProc(FilterContext* context, unsigned int eventType, void* eventData) {  
      switch (eventType) {  
           case kFilterTranslateRequest:  
                return QueryRewrite(context, (FilterMapURL *) eventData);  
           case kFilterRewriteURL:  
                return RewriteURL(context, (FilterMapURL *) eventData);  
           case kFilterResponse:  
                return ResponseHeaders(context, (FilterResponseHeaders *) eventData);  
                return kFilterNotHandled;  
 }     // end HttpFilterProc  

The rest of logic you can read yourself in SEOUrlHandler.c file. I've added information about how to compile DLL in readme on github. However If you have any question regarding some details let me know either via email or as a comment to this post. I will be glad to help.

Related topics
Rewriting URL in Domino using DSAPI
Solution for Lotus Domino to the trailing slash problem
Replacement for DSAPI in Java/XPages

Used materials
Domino Web Server Application Interface (DSAPI)

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