Jake,
Let's have these discussions on the newsgroup. That way more people
are likely to find it in the future when they do a search...
More comments below.
Jacob Beard wrote:
Hi Ed,
I have reviewed the resources you linked to. I believe I have a good
understanding of what would be required to expose EMF models using the
RESTful interfaces already available and HTTP. I'd appreciate it if you
(or Kenn), could please let me know if you feel like this sounds like a
reasonable solution.
Basically, you set up a Servlet inside of Eclipse that leverages the
Resource class that was mentioned in Kenn's presentation:
http://www.eclipsecon.org/2009/sessions?id=272
I'm not too sure where this class comes from. A quick search inside of
Eclipse showed a couple of Resource classes available in my workspace.
But, basically, you would use the one referenced by Kenn in his
presentation.
The EMF one of course: org.eclipse.emf.ecore.resource.Resource.
In each of the HTTP method handlers (GET, POST, PUT, DELETE), upon a
user request, you perform the following action: depending on what the
Resource class is able to accept, you may need to transform the http:
request URI to some other URI such as file: or platform: which the
Resource class can accept. You then send that URI into the Resource.
Yes, EMF provides a URIHandler that fully supports HTTP so a server
need only implement the full HTTP protocol. Most servers support only
read-only access...
If it's a PUT, you would instantiate a new resource at that URI. If
it's an HTTP GET, you would return that current resource, encoded in
XML or JSON.
Yes, it's just bytes as far as the transfer protocol is concerned. The
resource implementation itself determines the meaning of those bytes.
There is, for example, BinaryResourceImpl which supports a much smaller
and more efficiently processable representation.
If it's a POST, then you would assume that you're trying
to update an existing resource, and so would use a standard Remote
Procedure Calls pattern; you would retrieve the resource based on the
URL, then look at the post data for the method name and arguments to
invoke on the retrieved resource, then return the result as XML or
JSON.
We don't make use of POST. GET gets the bytes and PUT saves the bytes,
either overwriting an existing resource or creating a new resource.
Finally, a DELETE would retrieve the resource based on the
URI and then do whatever is needed to delete it.
I'm not sure it needs to retrieve anything. Just deleting it is good
enough.
I believe that the Servelet code that maps the HTTP methods onto the
restful interfaces can be generated automatically using the standard
genmodel.
I imagine such a mapping can be generic, just like the whole XML
serialization framework is completely generic. I.e., what will be
model-specific about this mapping?
Please let me know if this sounds reasonable. Thanks,
It sounds close. Let's use the newsgroup for follow ups. Maybe I'll
get a chance to visit Montreal one of these days. I haven't been there
for a great many years...
Jake
On Wed, Mar 25, 2009 at 3:20 PM, Jacob Beard
<jbeard4@xxxxxxxxxxxx>
wrote:
Hi
Ed,
Thanks again for the quick response. I'm currently reviewing the slides
from Kenn's presentation:
http://www.eclipsecon.org/2009/sessions?id=272
You're right, it probably would have been very helpful to have
attended. Maybe next year :)
I'll let you know if I still have questions on this. Thanks,
Jake
On Wed, Mar 25, 2009 at 2:01 PM, Ed Merks <ed.merks@xxxxxxxxx>
wrote:
On the other hand, you said that EMF's
resource design is fully
RESTful. Could you please explain this a bit more, or point me to a
resource that does?
Kenn's EclipseCon tutorial was about this topic. Why weren't you
there? :-P
In https://bugs.eclipse.org/bugs/show_bug.cgi?id=191077
there is a little servlet that I used to test that save and delete work
properly via HTTP.
In general REST is just a set of principles around the idea of how the
resources are uniformly addressed and the small number of operations
that can be applied to those resources. An EMF resource set
effectively works like a browser where pages are like resources,
addressed by a URI, and follow links opens new tabs. How more RESTful
can you be? :-P
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