----- Original Message -----
From: "Michael Pasternak" <mpastern@redhat.com> To: "Doron Fediuck" <dfediuck@redhat.com> Cc: engine-devel@ovirt.org, arch@ovirt.org Sent: Wednesday, February 20, 2013 2:56:59 PM Subject: Re: [Engine-devel] REST API calls from
On 02/14/2013 11:20 AM, Doron Fediuck wrote:
----- Original Message -----
From: "Michael Pasternak" <mpastern@redhat.com> To: "Libor Spevak" <lspevak@redhat.com> Cc: engine-devel@ovirt.org, arch@ovirt.org Sent: Wednesday, February 13, 2013 12:55:36 PM Subject: Re: [Engine-devel] REST API calls from the GUI
Hi Libor,
This issue came across in one of the conversations i had with UX folks, but since we didn't end up with any conclusion/road map (nor discussed it properly to hear other thoughts), this is a perfect place to start this discussion,
Intuitively REST is a way to go with GWT AJAX calls ---------------------------------------------------
pros ====
- api data objects can be reused by generating java classes (using jaxb) from the rest schema [1] - no backend logic will be duplicated as api abstracts the backend exposing RESTful collection/resources to operate on - development against api is "easy" as api describes itself in RSDL [2]
cons ====
- implementing transport layer (HTTP) under GWT - implementing own j2xml/json/yaml/... marshalling layer - implementing own error handling mechanism - implementing REST callback mechanism (in GWT) - constant maintenance of the data objects generated from the api - painful for Java developers
Java-SDK --------
pros ====
- abstracts transport layer (leaving developer in standard Java api) - typesafe code (no need to mess with XML bulks) - has own data objects to work with - abstracts authentication/authorization (kerberos/cookie/session/etc.) - since SDK is auto-generated, it can be easily extended with required features to support UI (such as callback infrastructure for instance)
cons ====
- has to be converted in to Javascript (not sure what the impacts are in terms of AJAX calls/etc.) - probably much more cons that we're not aware of and will have to figure out with POC
thoughts?
[1] http[s]://server[:port]/api?schema [2] http[s]://server[:port]/api?rsdl
Although started as a UI request, there are other needs who wish to use API calls with a different transport. For example a backend hook which gets a REST entry point it can use to fetch for additional data, or perform actions. In this case I'd expect an internal connection rather than creating additional connections. How would you resolve it generically enough in this context?
Doron,
I believe your approach a bit different, UX folks seeking for a convenient way of communicating with ovirt public api, e.g closing api<->GUI gap, and theirs alternatives where native HTTP layer or Java-SDK based framework, while what you need is in-process channel to communicate with the engine itself,
i understanding your will of using stable api for this (RESTapi), but not sure that doing this via JavaSDK is a good way to go simply because SDK is designed to operate in a client-space, while what you need is a server-space bridge for that.
Michael, true but... Thinking about it differently both UI and hooks needs a client. The underlying protocols should be abstracted. This is something which will serve other functions as well.
On 02/12/2013 06:13 PM, Libor Spevak wrote:
Hi,
I would like to ask, if there have been discussions about an option to call REST API services directly from the Frontend (GWT layer)? GWT compiles Java frontend-side to Javascript, calls to backend services are performed "transparently" by the framework using AJAX support. But, there is still a need to have a special set of data objects and the server-side logic can duplicate.
Java REST API SDK enables to build "thick" client. The calls are realized using e.g. Apache HttClient and supported libraries. I think the requirements of GWT can be a little bit different, but something overlaps.
I found several links about REST API support from GWT, so there is something for inspiration...
- http://www.spiffyui.org/ - http://www.zackgrossbart.com/hackito/gwt-rest/ - http://code.google.com/p/gwt-rest/ - http://restygwt.fusesource.org/
But, do you think it would be useful and what drawbacks can occur (authentication, authorization, response times, need to support larger set of services, painful refactoring, ...)?
Regards, Libor