Re: [Webware-devel] Filters for Webware
Chris, Thanks for the quick response -- I didn't expect to go in 0.9.2 -- no worries about that. Two things: 1) I *did* screw up the tabs/spaces in one of the files - FilterChain.py. I've attached a fixed version. Sorry. I've got Emacs set up to use spaces by default, and going back and forth is, um, tricky. Here's hoping (but not expecting) that this is the last such mistake. 2) Attached is the start of a tutorial/how-to style doc on using filters I'm attaching it in rough form to a) give a teaser for folks on this list who want to try filters out, and b) get feedback on whether or not this is a useful kind of doc. I'll keep working on this one, but if people are feeling like it's too simple, or would work better as part of a general Webware tutorial, let me know. -Dan from Common import * class FilterChain(Object): A FilterChain holds the specific, ordered list of Filters which are found to apply to a given request. They participate in transactions. XXX NOT IMPLEMENTED YET XXX It is intended that FilterChains can be created once, then used and destroyed, or they may be reused several times over (it's up to the server). Objects that participate in a transaction include: * Application * Request * Transaction * Session * Servlet * Response * FilterChain The awake(), respond() and sleep() methods form a message sandwich. Each is passed an instance of Transaction which gives further access to all the objects involved. ## Init ## def __init__(self): Subclasses must invoke super. Object.__init__(self) self._serverSidePath = None self._filters = [] ## Access ## def name(self): Returns the name which is simple the name of the class. Subclasses should *not* override this method. It is used for logging and debugging. return self.__class__.__name__ ## Filter Creation ## def addFilter(self, filter): self._filters.append(filter) ## Request-response cycles ## def awake(self, trans): This message is sent to all objects that participate in the request-response cycle in a top-down fashion, prior to respond(). self._transaction = trans for f in self._filters: f.awake(trans) def respond(self, trans): filters = self._filters next = Next(filters) first = filters[0] first.filter(trans, next) def sleep(self, trans): for f in self._filters: f.sleep(trans) #del self._filters ## Abilities ## def canBeThreaded(self): Returns 0 or 1 to indicate if the servlet can be multithreaded. This value should not change during the lifetime of the object. The default implementation returns 0. Note: This is not currently used. return 0 def canBeReused(self): Returns 0 or 1 to indicate if a single servlet instance can be reused. The default is 1, but subclasses con override to return 0. Keep in mind that performance may seriously be degraded if instances can't be reused. Also, there's no known good reasons not to reuse and instance. Remember the awake() and sleep() methods are invoked for every transaction. But just in case, your servlet can refuse to be reused. return 1 ## Server side filesystem ## def serverSidePath(self, path=None): Returns the filesystem path of the page on the server. if self._serverSidePath is None: if hasattr(self, _request) and self._request is not None: self._serverSidePath = self._request.serverSidePath() else: self._serverSidePath = self._transaction.request().serverSidePath() if path: return os.path.normpath(os.path.join(os.path.dirname(self._serverSidePath), path)) else: return self._serverSidePath ## Cleanup ## def clearTransaction(self): del self._transaction class Next(Object): def __init__(self, chain, curIdx = 0): Object.__init__(self) self._chain = chain self._curIdx = curIdx def __call__(self, trans): nextIdx = self._curIdx + 1 chain = self._chain if nextIdx len(chain): raise Exception(next called past end of FilterChain: %s % chain) nextFilter = chain[nextIdx] nextNext = Next(chain, nextIdx) nextFilter.filter(trans, nextNext) Filters in Webware Dan Milstein Overview Filters give you a simple, clean way to specify your own path-based request-handling pipeline. They are useful for authorization, for URL manipulation, for logging, and for many other situations. An Authorization example: Let's say the specification for overall, site-wide authorization looks something like the following: Users have to log in in order to view the site... ...except for content rooted at /public, which is openly accessible If a user has logged in, there will be a user_id stored in the session If a non-logged in user attempts to access a non-public page, they should be redirected to /Login After logging in, such a user should be taken to the page they originally requested The Code Create an AuthorizerFilter module with a class
Re: [Webware-devel] Filters for Webware
I like the idea of these filters, and I can definitely see how they could be useful. Having only looked at your examples and the doc you provided, though, I do have a couple of questions/suggestions. One, according to the documentation, you set up filters in Application.config. Would it be possible to use them in a per-servlet way? In other words, instead of setting the filters per instance in the config file, could I define a filter chain in the __init__ or awake() of an application's base class (some SitePage)? Two, although I'm sure I could figure it out by actually using the filters, you documentation does not quite tie all of the pieces together for me. For example, the first thing I though of when reading The Code section is Where does the import go? Where do I import the AuthorizerFilter that you set up in the config? I'd like to see a complete (but simple) example. I know that the docs are only preliminary, but that's my $.02USD. All-in-all, though, good job. It looks like a really handy tool to have. --John 2) Attached is the start of a tutorial/how-to style doc on using filters I'm attaching it in rough form to a) give a teaser for folks on this list who want to try filters out, and b) get feedback on whether or not this is a useful kind of doc. I'll keep working on this one, but if people are feeling like it's too simple, or would work better as part of a general Webware tutorial, let me know. -Dan - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Webware-devel mailing list Webware-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/webware-devel
Re: [Webware-devel] Filters for Webware
Thanks much for the response. Questions: One, according to the documentation, you set up filters in Application.config. Would it be possible to use them in a per-servlet way? In other words, instead of setting the filters per instance in the config file, could I define a filter chain in the __init__ or awake () of an application's base class (some SitePage)? I'm not sure if I fully understand this (and I'd like to). What would it mean for them to be per-servlet? Would that mean that the chain could depend on which servlet was actually called, rather than on which filters matched the URL? One of the strengths of the way it works now is it's actually important/useful to define behavior on the pattern of the URL. That's sort of the big win. Or am I misunderstanding? Could you talk out how you'd imagine using it in a per-servlet manner? Two, although I'm sure I could figure it out by actually using the filters, you documentation does not quite tie all of the pieces together for me. For example, the first thing I though of when reading The Code section is Where does the import go? Where do I import the AuthorizerFilter that you set up in the config? I'd like to see a complete (but simple) example. I know that the docs are only preliminary, but that's my $.02USD. Very helpful. Thanks. I'll take a pass at writing a small, complete application. In answer to your question: you don't ever have to import AuthorizerFilter -- Webware does so for you (so to speak) when it builds a chain which needs it. Your servlet code doesn't import or interact with the filter code directly. A filter can communicate with/influence servlet code, but only via the web data: a filter can modify the data in the request, or change the path, or store things in the session, or, if it wanted to do something really devious, could replace response/request objects in the transaction altogether. You could look at it as -- the filter can help set up the environment in which the servlet then executes. I'll try to make this all clearer in the docs. Thanks again -- very useful feedback. -Dan - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Webware-devel mailing list Webware-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/webware-devel
Re: [Webware-devel] Filters for Webware
In my initial excitement of the idea, I got a little ahead of myself. I see where you are coming from now, and why you define the filters in the config file. The big problem with putting a filter in a sevlet is that that same servlet might not have been accessed based on it's own filter. But the filter wouldn't have been called if you never loaded the servlet. Catch-22. However, I do think that there is value in being able to define a filter per-servlet. By this I mean that each sevlet could define behavior on it's own based on the path so far, with filters defined in Application.config serving as a default. Also, the filters could be processed down through the inheritance hierarchy. So the SitePage's filters would fire, then the MiddlePage's, and finally, assuming the filters allowed the request to get this far, the ChildPage's filter would be processed. But if I want that, maybe I should just use CherryPy ;-). They have (IMHO) a nice URL parsing system that seems very similar to this (at least functionally). I still like the idea of these filters in Webware (even if it's not per-servlet). --John I'm not sure if I fully understand this (and I'd like to). What would it mean for them to be per-servlet? Would that mean that the chain could depend on which servlet was actually called, rather than on which filters matched the URL? One of the strengths of the way it works now is it's actually important/useful to define behavior on the pattern of the URL. That's sort of the big win. Or am I misunderstanding? Could you talk out how you'd imagine using it in a per-servlet manner? - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Webware-devel mailing list Webware-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/webware-devel
[Webware-devel] Webware/Apache Threading Problem, Take II
So: I was having problems with large file uploads in my dev environment (OS X 10.4, Apache 2), and not in my production environment (Linux something, Apache 2). I have a bit more story, and I've resolved the problem. Here's the scoop, if you're interested: - I upgraded my apache install from 2.0.52 to 2.0.55 (using fink), and the problem went away No idea what random bug was fixed in apache which made this so, but things are working now. Just so everyone can know... -Dan - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Webware-devel mailing list Webware-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/webware-devel
Re: [Webware-devel] Webware/Apache Threading Problem, Take II
On Sep 18, 2006, at 1:43 PM, Dan Milstein wrote: So: I was having problems with large file uploads in my dev environment (OS X 10.4, Apache 2), and not in my production environment (Linux something, Apache 2). I have a bit more story, and I've resolved the problem. Here's the scoop, if you're interested: - I upgraded my apache install from 2.0.52 to 2.0.55 (using fink), and the problem went away No idea what random bug was fixed in apache which made this so, but things are working now. Even with the remaining mystery, that makes for a happy Monday, eh? - Mark - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Webware-devel mailing list Webware-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/webware-devel
