Re: [OpenMap Users] Corba support package

From: Don Dietrick <>
Date: Mon, 22 Aug 2005 10:06:25 -0400

Hi Mariusz,

When you use the SHIS and the SHISPlugIn you won't get caching of the
RPF frames on the client side. The client will go back to the server
for each projection change. Another thing to be aware of is that the
SimpleHttpImageServer was named like that on purpose - it's OK for
light loads, like a couple of clients hitting it at a moderate pace.
If you get several clients connecting to it, it will get
overwhelmed. You can create a servlet to handle greater client
loads, and that servlet can use the MapRequestHandler (like the
SimpleHttpImageServer) to create the images for you. If you need to
be able to handle greater client loading, you can create a pool of
MapRequestHandlers to handle multiple requests.

For the best performance for handing RPF data, I'd stick with the
RpfFrameProvider approach. If you are comfortable with CORBA, I'd
just use the CorbaRpfLayer talking to a CRFPServer. I doubt it would
be worth writing an RMI RpfFrameProvider mechanism just for some
performance difference between CORBA and RMI, but it might be worth
doing if configuring the client-server connection is easier for you
with the RMI approach.

As for an http approach, I suppose you could write a http
RpfFrameProvider, but then you'd have to deal with the other methods
that the RpfFrameProvider handles, and that might have it's own
challenges (using XML for communication protocol between client and
server, perhaps)?

As for configuring the HttpServer to send lower quality images, you
can do that if you are using a SunJpegImageFormatter, it has a
setting for image quality. Check the javadocs for the property.

- Don

On Aug 21, 2005, at 10:25 AM, Mariusz Chmielewski wrote:

> Thanks in advance for the answers i understand CORBA mechanisms and
> basic issues but i was asking for something else, i analyzed the
> code for corba server and client and i understand that server is
> usling local RpfFrameProvider and the client is the using the
> remote one. Most of all I need to understatn the functionality of
> the implemented interface and what should be done to transfer
> remotly the RPH frames what is done and what should be done. I
> already achived to load the map elements using the pair of
> SimpleHttpServer and the SHISPlugIn and it works fine except the
> one situation which i have described in previous mail. I wonder
> which method of providing data is faster RMI, CORBA or pure Http
> what do You thind since You have implemented it. Can i configure
> the HttpServer to send lower quality images???
> Thank You a lot Mariusz
> Don Dietrick napisaƂ(a):
>> Hi Mariusz,
>> On Aug 20, 2005, at 4:16 PM, Mariusz Chmielewski wrote:
>>> Hi everybody,
>>> I am trying to get in touch with anyone who used this packege. If
>>> someone has overloaded the mechanisms provieded in the example
>>> with full
>>> understaning I would be greatful for the hints. My biggest
>>> problem is
>>> the lack of the rest of sources for this packege (the full
>>> packege in
>>> jar is provided but in sources i cannot find anything).
>> All of the source code is there, it's just that some of it needs
>> to be generated. If you build the package with ant, the idl files
>> will be compiled to create the source fiies that are missing.
>> But those source files really won't help you with what you want to
>> do, they are the sources for how the CORBA mechanism handles the
>> objects between the server and client.
>>> I am trying to design the similar RMI based mechanism for
>>> wrorking with the CADRG map
>>> and i am not sure if i shout base the mechanism on
>>> SimpleHttpServer or
>>> provide the whole RMI mechanism as in CORBA example. I would like to
>>> state that the client softwer will be an applet and the server
>>> side will
>>> be chosen based on the best end effective method of providing the
>>> RPF
>>> map. On the client side i would like to have other layer such as
>>> graphics so i need the server side and the whole mechanism to
>>> provide
>>> the map data only.
>> Since you want to cache RPF data files on the applet, you should
>> definitely use the RMI mechanism. All you need is a modified
>> CRPFClient and CRPFServer that use the RMI mechanism instead of
>> the CORBA mechanism. The CRPFClient is the object that implements
>> the RpfFrameProvider interface, you just have to design your RMI
>> mechanism to support those methods. Then, you modify the
>> CorbaRpfLayer to use your client RpfFrameProvider instead of the
>> CRPFCient.
>> BTW, everyone that receives mail also receives
>> mail, so you don't have to send mail to both
>> lists.
>> - Don
>> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>> Don Dietrick,
>> BBN Technologies, Cambridge, MA
>> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> --
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Don Dietrick,
BBN Technologies, Cambridge, MA

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Received on Mon Aug 22 2005 - 10:10:23 EDT

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