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<title>Implementation of locate requests</title>
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<h1>Locate requests</h1>
<HR>
<h2>Context</h2>
The CORBA specification describes locate requests as a way to
find out if an object is available at the other end of the wire
or not without invoking an actual method on it.
This way expensive marshalling and demarshalling can be prohibited.
Locate requests are part of GIOP.
<h2>Implementation</h2>
The main classes involved in locate requests are the Server_Connection_Handler
to do check for the object. This is done by invoking the non standard
"non_existent" method on it. If it fails an exception will be thrown,
if the exception is not the Forward_Request exception of the POA,
the object is not there. If it is this specific exception, the new
forwarded location can be extracted and returned in the locate reply.
If the call on "non_existent" succeeds, we know the object is there and
return that.
The client part of the locate request is handled int Locate_Request_Invocation.
The response is checked on the answer. If there, we go on and invoke the
actual method on the distant object. If not there, we fail and throw the proper
exception and if we get forwarded we replace our IIOP profile acordingly.
<h2>API</h2>
To activate the locate requests, please invoke the non standard method
"_use_locate_requests (CORBA::B_TRUE)" on your CORBA::Object or any
object which inherits form this object. This will activate the locate
request on the first call to the object. The second time and on all
following calls "no" locate request will be used any more. To switch
it on again use "_use_locate_requests (CORBA::B_TRUE)" again.
You can also switch it of by "_use_locate_requests (CORBA::B_FALSE)".
<HR>
For more details and questions,
<p>
<address><a href="mailto:irfan1@cs.wustl.edu">Irfan Pyarali</a></address>
<p>
<address><a href="mailto:mk1@cs.wustl.edu">Michael Kircher</a></address>
<p>
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