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Java Forum / General / May 2005HTTP tunneling and Servlet communication
I am developing a J2EE app, front end is a fat client accross the internet. Until recently, I was planning to use RMI to communicate between f/end and server but after lots more reading I have decided against it (for reasons which would be obvious to anyone attempting to reply this post - so to keep the post brief, I'll skip enumerating them here). I want to use a servlet layer at the backend, because my client will almost definitely be behind a firewall/using a proxy server (I will therefore need http/s tunneling to communicate with clients). I have come up with a class which acts as a Facade to clients and presents a course simpler request/response API to clients. I have a Requset Factory which creates Asynch and Synch Requests. I am however stuck now and need some help. I am not sure how to convert my method call into an HTTP request (I have read several Servlet tutorials but still can't see a usefule xample that shows how a thick client can use a servlet - all examples seem to be about web browsers). Additionaly, I have not entirely worked out how I can "force" certain requests (i.e. SynchRequests) to be blocking. I have some ideas, but there are all pretty much hacks. i would be grateful for any ideas or pointers here. Lastly, whilst all this request/response is going on, I want to be "pushing" data from the server to the client through the same tunnel. Is this possible?. Can I send request/responses AND data on the same tunnel (presumably the same port)?. Tks i am not sure i completely understand ur design ... but I use Httpclient in a java thick client to communicate with a servlet or any http servers ... basically mimic a browser... ( apache.commons.httpclient ) -v > I am developing a J2EE app, front end is a fat client accross the > internet. Until recently, I was planning to use RMI to communicate [quoted text clipped - 7 lines] > therefore need http/s tunneling to communicate with clients). I have > come up with a class which acts as a Facade to clients and presents a > course simpler request/response API to clients. I have a Requset Factory > which creates Asynch and Synch Requests. I am however stuck now and need [quoted text clipped - 4 lines] > > Additionaly, I have not entirely worked out how I can "force" certain > requests (i.e. SynchRequests) to be blocking. I have some ideas, but > there are all pretty much hacks. i would be grateful for any ideas or > pointers here. > [quoted text clipped - 4 lines] > > Tks > I want to use a servlet layer at the backend, because my client will > almost definitely be behind a firewall/using a proxy server (I will [quoted text clipped - 6 lines] > usefule xample that shows how a thick client can use a servlet - all > examples seem to be about web browsers). did you look at SOAP? > Additionaly, I have not entirely worked out how I can "force" certain > requests (i.e. SynchRequests) to be blocking. I have some ideas, but > there are all pretty much hacks. i would be grateful for any ideas or > pointers here. well, http is actually synchronous, so your problem should be to do that non blocking > Lastly, whilst all this request/response is going on, I want to be > "pushing" data from the server to the client through the same tunnel. Is > this possible?. Can I send request/responses AND data on the same tunnel > (presumably the same port)?. I don't know if this is possible. The problem here is basically to get more http responses for one request, which is fairly hard. The only possibility I can think of is to send responses with the 100 status code. As far as I know, in that case it's possible to send more responses. >> I want to use a servlet layer at the backend, because my client will >> almost definitely be behind a firewall/using a proxy server (I will [quoted text clipped - 8 lines] > > did you look at SOAP? Yeah. Sorry, I should have mentioned that I did not want to use SOAP because of all the "weight" of the XML payload and also the extra XML procesing required on both ends. I want this to be as lightweight as I can get away with (securely). >> Additionaly, I have not entirely worked out how I can "force" certain >> requests (i.e. SynchRequests) to be blocking. I have some ideas, but [quoted text clipped - 3 lines] > well, http is actually synchronous, so your problem should be to do that > non blocking My bad. I should have read what I was typing before I sent the post ;-). You are entirely right - the problem is to make the calls asynch. I have ideas about how to do it - an obvious one would be spawning a new thread which actually executes the HTTPRequest command, returning to the user and then calling back the callee when the data arrives/times out etc, but I wanted to know if there is another (more elegant?) way. >> Lastly, whilst all this request/response is going on, I want to be >> "pushing" data from the server to the client through the same tunnel. [quoted text clipped - 5 lines] > possibility I can think of is to send responses with the 100 status > code. As far as I know, in that case it's possible to send more responses. No, that is not what I mean. I'm talking about a client sending a request and simultaneously receiving data that is being "pushed" from the server. The key here is that the data is being pushed or streamed from the server. It is a "push" model i.e. not the typical "pull" model. Again, of the top of my head - I think I could have the datastream listener running in another thread and then handling the streaming data as it arrives (maybe it is tagged differently?). Which also suggests the possible use of a buffer so that data dosen't get lost if the client is busy..... > Yeah. Sorry, I should have mentioned that I did not want to use SOAP > because of all the "weight" of the XML payload and also the extra XML > procesing required on both ends. I want this to be as lightweight as I > can get away with (securely). well, than you will have to do something similar; a servlet that gets HTTP requests that contain, in the body, the paramters. > My bad. I should have read what I was typing before I sent the post ;-). > You are entirely right - the problem is to make the calls asynch. I have > ideas about how to do it - an obvious one would be spawning a new thread > which actually executes the HTTPRequest command, returning to the user > and then calling back the callee when the data arrives/times out etc, > but I wanted to know if there is another (more elegant?) way. don't think so. This is the regular solution. > No, that is not what I mean. I'm talking about a client sending a > request and simultaneously receiving data that is being "pushed" from > the server. The key here is that the data is being pushed or streamed > from the server. It is a "push" model i.e. not the typical "pull" model. I think I understood correctly. The problem is that you don't have push in HTTP. What I can imagine is that the client sends a first request to the server, and then the server sends multiple responses. This might simulate a push model. > Again, of the top of my head - I think I could have the datastream > listener running in another thread and then handling the streaming data > as it arrives (maybe it is tagged differently?). Which also suggests the > possible use of a buffer so that data dosen't get lost if the client is > busy..... I'm not sure, but if you want to use streaming you should check how it works with a proxy. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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