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<h1>10 CORBA System and User Defined Exceptions</h1>
<h3><a name="id83036">10.1
System Exceptions</a></h3>
<p><span class="code">Orber</span>, or any other <span class="code">ORB</span>, may raise a <span class="code">System Exceptions</span>.
These exceptions contain status- and minor-fields and may not appear in the
operations raises exception IDL-definition.</p>
<h4>Status Field</h4>
<p>The status field indicates if the request was completed or not and will be
assigned one of the following Erlang atoms:</p>
<table border="1" cellpadding="2" cellspacing="0">
<tr>
<td align="left" valign="middle"><strong>Status</strong></td>
<td align="left" valign="middle"><strong>Description</strong></td>
</tr>
<tr>
<td align="left" valign="middle">'COMPLETED_YES'</td>
<td align="left" valign="middle">The operation was invoked on the target object but an error occurred after the object replied. This occur, for example, if a server replies but Orber is not able to marshal and send the reply to the client ORB.</td>
</tr>
<tr>
<td align="left" valign="middle">'COMPLETED_NO'</td>
<td align="left" valign="middle">Orber failed to invoke the operation on the target object. This occur, for example, if the object no longer exists.</td>
</tr>
<tr>
<td align="left" valign="middle">'COMPLETED_MAYBE'</td>
<td align="left" valign="middle">Orber invoked the operation on the target object but an error occurred and it is impossible to decide if the request really reached the object or not.</td>
</tr>
</table>
<em>Table
10.1:
System Exceptions Status</em>
<h4>Minor Field</h4>
<p>The minor field contains an integer (VMCID), which is related to a more
specific reason why an invocation failed. The function
<span class="code">orber:exception_info/1</span> can be used to map the minor code to a string.
Note, for VMCID:s not assigned by the OMG or Orber, the documentation
for that particular ORB must be consulted.</p>
<h4>Supported System Exceptions</h4>
<p>The OMG CORBA specification defines the following exceptions:</p>
<ul>
<li>
<strong>'BAD_CONTEXT'</strong> - if a request does not contain a correct
context this exception is raised.</li>
<li>
<strong>'BAD_INV_ORDER'</strong> - this exception indicates that operations
has been invoked operations in the wrong order, which would cause,
for example, a dead-lock.</li>
<li>
<strong>'BAD_OPERATION'</strong> - raised if the target object exists, but
that the invoked operation is not supported.</li>
<li>
<strong>'BAD_PARAM'</strong> - is thrown if, for example, a parameter is out
of range or otherwise considered illegal.</li>
<li>
<strong>'BAD_TYPECODE'</strong> - if illegal type code is passed, for example,
encapsulated in an any data type the <span class="code">'BAD_TYPECODE'</span> exception
will be raised.</li>
<li>
<strong>'BAD_QOS'</strong> - raised whenever an object cannot support the
required quality of service.</li>
<li>
<strong>'CODESET_INCOMPATIBLE'</strong> - raised if two ORB's cannot
communicate due to different representation of, for example,
<span class="code">char</span> and/or <span class="code">wchar</span>.</li>
<li>
<strong>'COMM_FAILURE'</strong> - raised if an ORB is unable to setup
communication or it is lost while an operation is in progress.</li>
<li>
<strong>'DATA_CONVERSION'</strong> - raised if an ORB cannot convert data
received to the native representation. See also the
<span class="code">'CODESET_INCOMPATIBLE'</span> exception.</li>
<li>
<strong>'FREE_MEM'</strong> - the ORB failed to free dynamic memory and
failed.</li>
<li>
<strong>'IMP_LIMIT'</strong> - an implementation limit was exceeded in the
ORB at run time. A object factory may, for example, limit the
number of object clients are allowed to create.</li>
<li>
<strong>'INTERNAL'</strong> - an internal failure occurred in an ORB, which
is unrecognized. You may consider contacting the ORB providers
support.</li>
<li>
<strong>'INTF_REPOS'</strong> - the ORB was not able to reach the interface
repository, or some other failure relating to the interface
repository is detected.</li>
<li>
<strong>'INITIALIZE'</strong> - the ORB initialization failed due to, for
example, network or configuration error.</li>
<li>
<strong>'INVALID_TRANSACTION'</strong> - is raised if the request carried an
invalid transaction context.</li>
<li>
<strong>'INV_FLAG'</strong> - an invalid flag was passed to an operation,
which caused, for example, a connection to be closed.</li>
<li>
<strong>'INV_IDENT'</strong> - this exception indicates that an IDL
identifier is incorrect.</li>
<li>
<strong>'INV_OBJREF'</strong> - this exception is raised if an object
reference is malformed or a nil reference (see
also corba:create_nil_objref/0).</li>
<li>
<strong>'INV_POLICY'</strong> - the invocation cannot be made due to an
incompatibility between policy overrides that apply to the
particular invocation.</li>
<li>
<strong>'MARSHAL'</strong> - this exception may be raised by the client- or
server-side when either ORB is unable to marshal/unmarshal requests or
replies.</li>
<li>
<strong>'NO_IMPLEMENT'</strong> - if the operation exists but no implementation
exists, this exception is raised.</li>
<li>
<strong>'NO_MEMORY'</strong> - the ORB has run out of memory.</li>
<li>
<strong>'NO_PERMISSION'</strong> - the caller has insufficient privileges,
such as, for example, bad <span class="code">SSL</span> certificate.</li>
<li>
<strong>'NO_RESOURCES'</strong> - a general platform resource limit
exceeded.</li>
<li>
<strong>'NO_RESPONSE'</strong> - no response available of a deferred
synchronous request.</li>
<li>
<strong>'OBJ_ADAPTER'</strong> - indicates administrative mismatch; the object
adapter is not able to associate an object with the implementation
repository.</li>
<li>
<strong>'OBJECT_NOT_EXIST'</strong> - the object have been disposed or
terminated; clients should remove all copies of the object reference
and initiate desired recovery process.</li>
<li>
<strong>'PERSIST_STORE'</strong> - the ORB was not able to establish a
connection to its persistent storage or data contained in the
the storage is corrupted.</li>
<li>
<strong>'REBIND'</strong> - a request resulted in, for example, a
<span class="code">'LOCATION_FORWARD'</span> message; if the policies are incompatible
this exception is raised.</li>
<li>
<strong>'TIMEOUT'</strong> - raised if a request fail to complete within the
given time-limit.</li>
<li>
<strong>'TRANSACTION_MODE'</strong> - a transaction policy mismatch detected.</li>
<li>
<strong>'TRANSACTION_REQUIRED'</strong> - a transaction is required for the
invoked operation but the request contained no transaction context.</li>
<li>
<strong>'TRANSACTION_ROLLEDBACK'</strong> - the transaction associated with
the request has already been rolled back or will be.</li>
<li>
<strong>'TRANSACTION_UNAVAILABLE'</strong> - no transaction context can be
supplied since the ORB is unable to contact the Transaction
Service.</li>
<li>
<strong>'TRANSIENT'</strong> - the ORB could not determine the current status
of an object since it could not be reached. The error may be
temporary.</li>
<li>
<strong>'UNKNOWN'</strong> - is thrown if an implementation throws a
non-CORBA, or unrecognized, exception.</li>
</ul>
<h3><a name="id83473">10.2
User Defined Exceptions</a></h3>
<p>User exceptions is defined in IDL-files and is listed in operations raises
exception listing. For example, if we have the following IDL code:</p>
<div class="example"><pre>
module MyModule {
exception MyException {};
exception MyExceptionMsg { string ExtraInfo; };
interface MyInterface {
void foo()
raises(MyException);
void bar()
raises(MyException, MyExceptionMsg);
void baz();
};
};
</pre></div>
<h3><a name="id83493">10.3
Throwing Exceptions</a></h3>
<p>To be able to raise <span class="code">MyException</span> or <span class="code">MyExceptionMsg</span> exceptions,
the generated <span class="code">MyModule.hrl</span> must be included, and typical usage is:</p>
<div class="example"><pre>
-module('MyModule_MyInterface_impl').
-include("MyModule.hrl").
bar(State) ->
case TestingSomething of
ok ->
{reply, ok, State};
{error, Reason} when list(Reason) ->
corba:raise(#'MyModule_MyExceptionMsg'{'ExtraInfo' = Reason});
error ->
corba:raise(#'MyModule_MyException'{})
end.
</pre></div>
<h3><a name="id83525">10.4
Catching Exceptions</a></h3>
<p>Depending on which operation we invoke we must be able to handle:</p>
<ul>
<li>foo - <span class="code">MyException</span> or a system exception.</li>
<li>bar - <span class="code">MyException</span>, <span class="code">MyExceptionMsg</span> or a system
exception.</li>
<li>baz - a system exception.</li>
</ul>
<p>Catching and matching exceptions can bee done in different ways:</p>
<div class="example"><pre>
case catch 'MyModule_MyInterface':bar(MIReference) of
ok ->
%% The operation raised no exception.
ok;
{'EXCEPTION', #'MyModule_MyExceptionMsg'{'ExtraInfo' = Reason}} ->
%% If we want to log the Reason we must extract 'ExtraInfo'.
error_logger:error_msg("Operation 'bar' raised: ~p~n", [Reason]),
... do something ...;
{'EXCEPTION', E} when record(E, 'OBJECT_NOT_EXIST') ->
... do something ...;
{'EXCEPTION', E} ->
... do something ...
end.
</pre></div>
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