All, I'm in the process of constructing a filter that logs context access to a database, but I'm running into a bit of trouble.
First off, if anyone knows of any free filters that do this, then I'm barking up the wrong tree. I don't want to reinvent the wheel! (And I can't believe this isn't a common thing.) Most of the information that you'd need for an access log is readily available in the request and response objects, however two common metrics are (seemingly) difficult to get to, namely the response size (in bytes) and the response HTTP status code. I won't wail on how the response object should have a "getStatus()" and "getResponseSize()" magic methods; they probably aren't in the spec (I haven't bothered to check). I figured my optimal solution was a filter, since I'd like this thing to be somewhat portable. (Tomcat valves aren't portable, correct?) Now, I have read "The Essentials of Filters" (http://java.sun.com/products/servlet/Filters.html), and believe that I understand it well enough, and I have also looked at the source for the Compression filter. For the status code, my wrapper has overridden the setStatus(int sc) and sendError(int sc)/sendError(int sc, String message) methods. I trap the status code as appropriate and then pass the values right on through to the original response. Then it's a simple matter of adding a getStatus() method on my wrapper to obtain the status. For the response size, I had to also write a wrapper class extending ServletOutputStream. This class takes a ServletOutputStream as an argument to the constructor, which is then stored as a protected member (named "output"). The write() method was implemented to increment a long by 1 every time the method is called, then immediately pass the argument right along to the "output" member. write(int b) was the only method that I overrode. I also added a method to retrieve the long that was incremented each time write() was called, thus telling me how many bytes were sent to the client. I have also tried simply overriding the setContentLength() method in my response wrapper, but this wasn't entirely successful, as you'll see in my problems below. My problems are this: 1. Somehow HTTP status codes of 200 (SC_OK) are set without being properly trapped by the response wrapper. I have to set a default value of 200 in the wrapper, which I'd rather not do. Redirects, page-not-found, etc., are properly trapped. 2. The response size measurement is completely off. Trapping setContentLength() in the response wrapper seems to not catch every case (404's and 500's don't seem to call setContentLength(), or they call it before I create the wrapper). The stream wrapper is similarly inaccurate, in that error pages don't seem to call the write() method. Probably both issues are related. Is my approach too simple-minded? Am I trying to do too much with what's available to a filter? Is this something that's more properly suited to a valve? Thanks for your help, and sorry for the length. Brantley Hobbs --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
