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Java Forum / General / December 2005replacing duplicate object on client
Client Server - client is MVC server holds objects of same type as are contained in the M of clients MVC For the sake of this thread lets assume this is a reasonable design for my system. Object arrives at client and is equivalent but obviously more upto date than one already held by client. Client wants to replace the old one with the new one. Does it: a/ copy all the observers out of the old one into the new one and replace the object b/ copy the data out of the new one into the old one c/ replace the object and let some other observer mechanism sort refresh whatever d/ something else I haven't considered. TIA -- Mike W How do we know what it does? You programmed it. Unless this is some sort of brand-named server you forgot to mention? Let us know. ;) > How do we know what it does? http://en.wikipedia.org/wiki/Abstraction -- Mike W So what does this have to do with your post? > So what does this have to do with your post? I think VisionSet is saying you don't need to know what his program does to answer the specific design question of how to synchronize two different model objects. - Oliver An attempt at good grammar goes a long way I guess. Sounded like he already had a server, and wanted to know how it worked. > An attempt at good grammar goes a long way I guess. > Sounded like he already had a server, and wanted to know how it worked. You should quote who you are replying to. That goes a long way too -- LTP :) Yep. FYI, I was referring to the original post. <copy> Client Server - client is MVC server holds objects of same type as are contained in the M of clients MVC For the sake of this thread lets assume this is a reasonable design for my system. Object arrives at client and is equivalent but obviously more upto date than one already held by client. Client wants to replace the old one with the new one. Does it: a/ copy all the observers out of the old one into the new one and replace the object b/ copy the data out of the new one into the old one c/ replace the object and let some other observer mechanism sort refresh whatever d/ something else I haven't considered. TIA  SignatureMike W </copy> > Client Server - client is MVC server holds objects of same type as are > contained in the M of clients MVC [quoted text clipped - 15 lines] > whatever > d/ something else I haven't considered. I would go with 'b'. For your client-side model object, I'd have a method "updateFrom(Model m)" or something like that, so all you have to do is pass in the new Model object into the old one, then discard the new Model object. The updateFrom() method should take care of only sending notifications for the fields that actually did change. - Oliver > a/ copy all the observers out of the old one into the new one and replace > the object > b/ copy the data out of the new one into the old one > c/ replace the object and let some other observer mechanism sort refresh > whatever > d/ something else I haven't considered. Probably (c) and/or (d). You already have code that connects your client code to a model (or how come it is already observing the old model). Run that code again with the new model. If it takes more than one line of new code then you've done something wrong ;-) -- chris > > a/ copy all the observers out of the old one into the new one and replace > > the object [quoted text clipped - 7 lines] > again with the new model. If it takes more than one line of new code then > you've done something wrong ;-) I guess that is the best general approach, just that the 1st time the object is installed on the client an observer mechanism causes new gui components to be created to render it. Subsequent updates shouldn't create new GUI elements or even have any gui component destruction/creation effect, just trigger paint updates. Just need to think a bit harder about this one. I guess it will be a case of firing an insert or an update sort of event and letting the gui figure it out. -- Mike W > a/ copy all the observers out of the old one into the new one and replace > the object > b/ copy the data out of the new one into the old one > c/ replace the object and let some other observer mechanism sort refresh > whatever > d/ something else I haven't considered. You probably want to keep the object identity intact if there are users of it. So I would tend towards b. Replication is quite difficult. If you can guarantee good enough quality of communication, thing become easier if you can make sure that all modifications are done either in one place or with distributed locks enforced. A handy strategy is to replay the actions that caused the mutations, rather than trying to compare data. Another useful (and indeed have good performance from the client view of things) approach is to forget about small scale listeners and just sync the whole lot. It can mean much less code without all those listeners. It has good performance because there isn't the high set up time and in the case of lots changing there aren't all those events, just a single process. It's much slower on smaller updates, but who cares about performance of what will be fast anyway. Tom Hawtin SignatureUnemployed English Java programmer http://jroller.com/page/tackline/ Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. 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