Re: Servlet filter and listerner best practices
From: Etienne [EMAIL PROTECTED] Sent: Friday, February 21, 2003 3:47 AM Subject: Servlet filter and listerner best practices Hi all, I am looking for some best practices for servlet filter (and servlet listener). These are quite new (servlet 2.3). I am using a servlet filter on some of my jsp page, but I would need a detail example of the best way to implement it. It kind of all depends on what your Filter needs to do. Passive filters (like, say, a Logging Filter) can be quite different from something like a GZip filter, which needs to really muck about with the request and streams and what not. I am not sure how to catch exception in the servlet filter without hiding everything in the back on it. Pretty standard exception technique here. If you catch an exception that you don't want to deal with, simply throw it again and let something else higher up take care of it. Even better, don't catch exceptions that you can't handle at all. The old proclamation of Don't test for something you can't handle rings loudly here. Perhaps some more detail about your situation would be helpful. Is there a more precise way (with some reg ex?) to associate a filter with pages? I dunno, the filter specification is pretty specific, perhaps too specific meaning that for lots of disparate pages, you'll have lots of entries in the web.xml. Perhaps if you could organize your pages in a hierarchy so you could simply put the filter on a parent directory part of the path would help reduce the load on the web.xml file. Regards, Will Hartung ([EMAIL PROTECTED]) - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: Servlet filter and listerner best practices
Thanks Will, The filter servlet is only for logging checking and parameter init. I would have like to learn more about (J2EE) pattern using filter and listener servlet. The problem about the filter servlet is that doFilter() do not throws exception, so we must catch everything in doFilter. So that is why I was hiding everything in back of it. It can be hard to debug that way. Regards, Etienne -Original Message- From: Will Hartung [mailto:willh@x] Sent: February 21, 2003 12:36 PM To: Tomcat Users List Subject: Re: Servlet filter and listerner best practices From: Etienne etienno@ Sent: Friday, February 21, 2003 3:47 AM Subject: Servlet filter and listerner best practices Hi all, I am looking for some best practices for servlet filter (and servlet listener). These are quite new (servlet 2.3). I am using a servlet filter on some of my jsp page, but I would need a detail example of the best way to implement it. It kind of all depends on what your Filter needs to do. Passive filters (like, say, a Logging Filter) can be quite different from something like a GZip filter, which needs to really muck about with the request and streams and what not. I am not sure how to catch exception in the servlet filter without hiding everything in the back on it. Pretty standard exception technique here. If you catch an exception that you don't want to deal with, simply throw it again and let something else higher up take care of it. Even better, don't catch exceptions that you can't handle at all. The old proclamation of Don't test for something you can't handle rings loudly here. Perhaps some more detail about your situation would be helpful. Is there a more precise way (with some reg ex?) to associate a filter with pages? I dunno, the filter specification is pretty specific, perhaps too specific meaning that for lots of disparate pages, you'll have lots of entries in the web.xml. Perhaps if you could organize your pages in a hierarchy so you could simply put the filter on a parent directory part of the path would help reduce the load on the web.xml file. Regards, Will Hartung (willh@x) - To unsubscribe, e-mail: tomcat-user-unsubscribe@xx For additional commands, e-mail: tomcat-user-help@xx - To unsubscribe, e-mail: tomcat-user-unsubscribe@xx For additional commands, e-mail: tomcat-user-help@xx
Re: Servlet filter and listerner best practices
From: Etienne etienno@ Sent: Friday, February 21, 2003 11:06 AM Subject: RE: Servlet filter and listerner best practices Thanks Will, The filter servlet is only for logging checking and parameter init. I would have like to learn more about (J2EE) pattern using filter and listener servlet. Logging is pretty simple, as you simply Do Your Thing either before or after the doFilter call (or both). Here the Filter is a simple wrapper. I think they're handy for doing the parameter parsing and creating a local instance of a specific Parameter class that your code relies on. This helps loosen up the binding between your logic and the fact that it's buried in a Servlet container. Of course, you still need to pass in the Parameter, I stuff it into the Request as an attribute. The problem about the filter servlet is that doFilter() do not throws exception, so we must catch everything in doFilter. So that is why I was hiding everything in back of it. It can be hard to debug that way. Well, it can throw a ServletException, which is the same as the Servlet.service() method, though service() also can throw an IOException, so you're really not losing anything. Mind I'm not saying that it can't be limiting, but it's just not that much more limiting than the normal happenings within Servlet programming. Regards, Will Hartung (willh@x) - To unsubscribe, e-mail: tomcat-user-unsubscribe@xx For additional commands, e-mail: tomcat-user-help@xx
