Barry - thanks for the report
On 28/01/2020 19:28, Nouwt, B. (Barry) wrote:
Hi all,
I enabled CORS on embedded Fuseki (when handling YASGUI SPARQL requests) and
wanted to share the way I did it for others' benefit. It took me a while to
figure out how to do this. I found instructions on how to enable CORS via the
web.xml, but the embedded Fuseki does not use a web.xml (as far as I am aware).
I also found a lot of examples on how to add the CORS filter in Jetty when you
control when filters are added. The code at the end of the email enables it in
my setup.
You are correct - Fuseki main is not a webapp, no war file.
Fuseki Full, a webapp, does put the CORS filter in.
I thought that servlet filters got added before the Fuseki main filter
but it sounds like that is not your experience. That would be a bug.
Could you file a JIRA please? As your code show, getting the order right
is ... a bit opaque.
The complication is that the Fuseki filter catches "/*" (any URL)
because the valid names can change as datasets are added to registry
which is possible at run time.
It might need both "before" and "after" filters.
And/or : It might be a good idea to have an "enableCORS" setting to the
Fuseki Server builder which will need its own configuration.
Andy
Some remarks:
- as far as I could see, Fuseki builder does not allow custom filters to be
chained/configured before the FusekiFilter (which intercepts all traffic to
datasets).
- adding the CORS filter after the FusekiFilter does not work in case of a
SPARQL request to a particular dataset, because FusekiFilter intercepts its and
prevents it from continuing through the filter chain.
- the above two remarks forced me to add the CORS filter directly to the Jetty
Server, however, it does not allow insertion of filters before other filters,
it only supports adding it to the end of the chain.
- After succeeding to add my filter before the FusekiFilter, it still did not
work, because (after some searching) a FilterMapping (to a particular path) is
also required.
- So, the not so elegant code below retrieves both the filters and the
filtermappings and inserts the filter (and filtermapping) before the
FusekiFilter.
Maybe someone can check whether there is an easier way to enable it and
hopefully it saves somebody a few hours in the future!
Regards, Barry
----------- code to enable CORS for embedded fuseki (note that this code is not
directly runnable)------------------------------
//... configure server through builder ...
server = builder.build();
Server jettyServer = server.getJettyServer();
/*
* trying to add the cross origin filter. Fuseki adds its FusekiFilter as the
* first and this one consumes a SPARQL request to a particular dataset. So, to
* be able to add the cross origin filter, we have to add it BEFORE the
* FusekiFilter. This is not as easy as it looks, because you need to add the
* filter as a filter and as a filtermapping to the /* pathspec.
*/
Handler handler = jettyServer.getHandler();
FilterHolder holder = new FilterHolder(CrossOriginFilter.class);
// we use the default CrossOriginFilter settings, but you can specify them.
//holder.setInitParameter(CrossOriginFilter.ALLOWED_ORIGINS_PARAM, "*");
//holder.setInitParameter(CrossOriginFilter.ACCESS_CONTROL_ALLOW_ORIGIN_HEADER,
"*");
//holder.setInitParameter(CrossOriginFilter.ALLOWED_METHODS_PARAM,
"GET,POST,HEAD,OPTIONS");
// holder.setInitParameter(CrossOriginFilter.ALLOWED_HEADERS_PARAM,
// "X-Requested-With,Content-Type,Accept,Origin");
assert (handler instanceof ServletContextHandler);
ServletContextHandler h = (ServletContextHandler) handler;
ServletHandler servletHandler = h.getServletHandler();
List<FilterMapping> mappings = new
ArrayList<FilterMapping>(Arrays.asList(servletHandler.getFilterMappings()));
List<FilterHolder> holders = new
ArrayList<FilterHolder>(Arrays.asList(servletHandler.getFilters()));
FilterMapping mapping = new FilterMapping();
mapping.setFilterName(holder.getName());
mapping.setPathSpec("/*");
mapping.setDispatcherTypes(EnumSet.of(DispatcherType.REQUEST));
mappings.add(0, mapping);
holders.add(0, holder);
FilterMapping[] mappings3 = new FilterMapping[mappings.size()];
mappings3 = mappings.toArray(mappings3);
FilterHolder[] holders3 = new FilterHolder[holders.size()];
holders3 = holders.toArray(holders3);
servletHandler.setFilters(holders3);
servletHandler.setFilterMappings(mappings3);
server.start();
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