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<TITLE>Fault Handling</TITLE>
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<H2 align="center">Fault Handling</H2>
<P>Occasionally something will go wrong on the
server side, whether it is due to an errant
service implementation, a bad client request,
or perhaps just normal operating difficulties.
The SOAP specification provides for the communication
of these errors through the transmittal of
a SOAP Fault body element within a SOAP Envelope.
The Apache SOAP server will attempt to capture
an error state and then construct a SOAP
Fault message containing a base set of information
about the error which occurred. However,
sometimes it is useful to augment the fault
information for a particular service or to
perform one or more additional tasks when
an error state arises. To allow for this
type of flexibility, the Apache SOAP server
provides a pluggable fault handling mechanism
into which one or more fault listeners may
be registered to process faults. (The pluggable
fault handling mechanism in Apache SOAP works
on on the event/listener model.)</P>
<P>Apache SOAP provides two basic fault handlers:
</P>
<UL>
<LI>org.apache.soap.server.DOMFaultListener
<LI>org.apache.soap.server.ExceptionFaultListner
</UL>
<P>Both of these augment the SOAP Fault message
with additional information about the fault;
the first by adding a DOM element representing
the root exception which occurred, and the
second by wrappering the root exception in
a Parameter. Most people will probably find
the first to be more useful.</P>
<H3>Registering Fault Handlers</H3>
<P>Fault handlers are registered by including
one or more <faultListener> elements
within the deployment descriptor of a service.
For more information about adding fault handlers
to the deployment descriptor, look <A href="deploy.html">here</A>.</P>
<H3>Creating New Fault Handlers</H3>
<P>Creating a new fault handler is simply a
matter of creating a Java class which implements
the org.apache.soap.server.SOAPFaultListener
interface. The single method which you need
to implement, fault, takes in a SOAPFaultEvent.
The SOAPFaultEvent wraps the SOAP Fault and
SOAP Exception objects which were created
due to the error. Once you've created the
fault handler, you'll need to register it
as indicated above.</P>
<P>Last updated 5/20/2001 by Bill Nagy <<A href="mailto:nagy@watson.ibm.com">nagy@watson.ibm.com</A>>.</P>
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