There's no rule that says faults should be used for system level
exceptions. It might be easier and neater for your application to
just throw faults, it really depends on how much detail you want to
provide back to the client.
On 3/13/07, Christopher Moesel <[EMAIL PROTECTED]> wrote:
This is not specifically related to XFire, but I value XFire users' and
developers' opinions, so I hope you do not mind me asking here.
I am working on the design of our exception and error handling in web
services. One thing I am dealing with is the decision as to when to return
faults versus when to return a status element indicating an error.
It seems to be a popular opinion that faults should be reserved for system
exceptions (that is, unexpected errors) and status elements should be used
for application exceptions (those errors that are expected to occur in
regular business interactions). While I agree that this seems a good idea,
I've run into one problem. Here is an example:
Suppose I have an operation called GetTodaysRedSoxScore. The response XSD
might look like this:
<xsd:complexType name="GetTodaysRedSoxScoreResponseType">
<xsd:sequence>
<xsd:element name="Status" type="tns:StatusType" />
<xsd:element name="Opponent" type="xsd:string" />
<xsd:element name="SoxScore" type="xsd:int" />
<xsd:element name="OpponentScore" type="xsd:int" />
</xsd:sequence>
</xsd:complexType>
Now suppose that someone invokes this operation on the Red Sox's day off.
Since this is really an application-level exception, many would say we
should return a status indicating "NO_GAME_SCHEDULED" or something like that
(instead of using a fault). BUT… Opponent, SoxScore, and OpponentScore are
all required elements… So I have about 4 choices:
(1) Exclude these elements from my response (thus returning XML that is not
valid against my own schema)
(2) Return default values for the required elements (empty string for
string, 0 or -1 for int, etc)
(3) Change the XSD to make all elements nillable
(4) Change the XSD to make all elements minOccurs="0"
I don't really like any of these options, so I'm tempted to use a fault,
even though it's not a system level exception.
Is there a best practice that anyone is aware of?
-Chris
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