What to do if an exception mapper throws an exception
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diff --git a/spec/chapters/resources.tex b/spec/chapters/resources.tex
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@@ -137,7 +137,7 @@
\begin{enumerate}
\item Instances of \WebAppExc\ MUST be mapped to a response as follows. If the \code{response} property of the exception does not contain an entity and an exception mapping provider (see section \ref{exceptionmapper}) is available for \WebAppExc\, an implementation MUST use the provider to create a new \Response\ instance, otherwise the \code{response} property is used directly. The resulting \Response\ instance is then processed according to section \ref{resource_method_return}.
-\item If an exception mapping provider (see section \ref{exceptionmapper}) is available for the exception or one of its superclasses, an implementation MUST use the provider whose generic type is the nearest superclass of the exception to create a \Response\ instance that is then processed according to section \ref{resource_method_return}.
+\item If an exception mapping provider (see section \ref{exceptionmapper}) is available for the exception or one of its superclasses, an implementation MUST use the provider whose generic type is the nearest superclass of the exception to create a \Response\ instance that is then processed according to section \ref{resource_method_return}. If the exception mapping provider throws an exception while creating a \Response\ then return a server error (status code 500) response to the client.
\item\label{runtimeexc} Unchecked exceptions and errors MUST be re-thrown and allowed to propagate to the underlying container.
\item\label{checkedexc} Checked exceptions and throwables that cannot be thrown directly MUST be wrapped in a container-specific exception that is then thrown and allowed to propagate to the underlying container. Servlet-based implementations MUST use \code{Servlet\-Exception} as the wrapper. JAX-WS \code{Provider}-based implementations MUST use \code{Web\-Service\-Exception} as the wrapper.
\end{enumerate}
