Hi William,
The response type of an SWP service is fixed, so a JSON service still should
return JSON in case of error.
The HTTP response status code can be set using ui:setResponseHeader:
<ui:setResponseHeader ui:statusCode="{= 404 }"/>
Personally I would say that a simple JSON object of the form {"error":"No
results found"} with an appropriate status code is a perfectly good response
and should be easy enough to handle by the service’s clients.
FWIW, here is an idiomatic way of checking for an empty SPARQL result set:
<ui:group let:rs="{# … }">
<ui:if ui:condition="{= spr:isEmpty(?rs) }">
… handle empty result set …
</ui:if>
<ui:else>
...
<ui:forEach ui:resultSet="{= ?rs }">
...
</ui:forEach>
...
</ui:else>
</ui:group>
Hope that helps,
Richard
> On 12 Nov 2018, at 19:30, William Ramos <[email protected]> wrote:
>
> Hi, community;
>
> I have a SWON service which contains a SPARQL query, in case the query is not
> empty the service responds with a JSON object. But in case the query is empty
> I would like to return a non JSON response, ideally an HTTP 404 with a
> payload message like "No results found."
>
> Is it possible to change the response type dynamically to achieve this?
>
> For reference, the service ui:prototype is like this:
> <ui:group>
> <ui:setGlobalVar ui:name="empty" ui:value="{= xsd:boolean(true) }"/>
> <ui:forEach ui:resultSet="{#
> ...
> }" ui:separator=",">
> <ui:setGlobalVar ui:name="empty" ui:value="{= xsd:boolean(false) }"/>
> <swon:Object>
> ...
> </swon:Object>
> </ui:forEach>
> <ui:if ui:condition="{= ui:globalVarValue("empty") = true }">
> <swon:Object>
> <swon:Value arg:name="Error" arg:value="No results found."/>
> </swon:Object>
> </ui:if>
> </ui:group>
>
> Thanks in advance.
>
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