On 11/19/2014 06:11 PM, Christian Sadilek wrote:

Hi Juan,

I have had this argument many times and to me it does not come down to “coupling” vs. “no coupling” but to “implicit coupling” vs. “explicit coupling”.

Even if you don’t use a shared interface (and, btw, you don’t have to share the interface in Errai) you still have coupling. In most cases, you can’t simply change the server-side REST endpoint without breaking existing clients and without changing your JavaScript code. The difference here is merely that in Errai it will fail at compile time while in other cases you will fail at runtime.

Cheers, Christian

I don't have any objection to use JAX-RS, Errai or any other client side technology. My concern is about using the server *implementation classes*, that is probably what you describe as "explicit coupling". The Java interfaces that we currently use are by no means intended for use outside of the server, they are an implementation details. We don't have (and won't have) any commitment to keep them backwards compatible, or to keep them at all, or even to keep JAX-RS (in the server side). So using those interfaces, for any purpose other than the server side implementation, is extremely risky. It would be nice to have the oVirt RESTAPI defined as an stable set of Java interfaces (with or without JAX-RS) and enjoy type safety and compile type checks, but that is not the case today (and it won't be in the 3.6 time frame). Today the only stable definition is the XML schema and the RSDL. That we commit to keep backwards compatible. As I said this doesn't mean that you can't use Errai JAX-RS, just that if you do so you will have to create and maintain your own interfaces.

On Nov 19, 2014, at 11:15 AM, Juan Hernandez <jhernand@redhat.com <mailto:jhernand@redhat.com>> wrote:

...

On 11/19/2014 04:58 PM, Martin Betak wrote:

...

Hi all,

I've been exploring the possibilities of utilizing Errai JAX-RS for REST client in our current GWT-based frontend. This would be a complement to Vojtech's oVirt.js library which is very native to javascript and utilizes dynamic discovery of resources and actions.

Errai JAX-RS would enable us to reuse our restapi definitions of resource interfaces and entities and generate proxies automatically thus eliminating the need for extensive manual code generation.

I strongly discourage this approach, as it will couple the client and the RESTAPI server implementation classes, similar coupling to what we have today between the client and the backend entities and parameters classes.

The contract of the RESTAPI is the XML schema that defines the entities and the RSDL that defines resources and actions. Everything else is subject to change and there is (and won't be) any backwards compatibility commitment. The resource interfaces in particular are not part of the contract, they are internal implementation details.

If you eventually decide to go this direction then you should create your own resource interfaces.

...

[errai jax-rs] https://docs.jboss.org/author/display/ERRAI/Errai+JAX-RS

Unfortunately in my quest I stumbled upon some issues I couldn't exactly google or solve and I would like to ask Mark or Christian, whether the below is somehow possible with Errai:

1) Adding custom header to every request (some form of request interceptors) You, see our api returns by default XML and we of course want to consume JSON. Thus adding 'Content-Type: application/json' as well as other custom authentication headers is necessary for our usage.

2) Using custom JSONProvider/ObjectMapper instead of the default Jackson one. In our JSONProvider [1] we use custom ObjectMapper [2] mainly to map JAX-B annotations to json. Without this for example errai generates marshaller for the VMs resource

public class VMs { @XmlElement(name = "vm") protected List<VM> vMs; }

that expects json field called "vMs" instead of the JAX-B specification "vm" which is the actual format returned from the API. There may be other differencies such as [3] so I think the best solution would be if we could tell errai to use specific JSONProvider for generating the marshallers.

This are the issues that so far seem to be the most blocking ones, others may arise along the way.

Thank you for any help provided.

Best regards,

Martin

[1] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/re... [2] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/re... [3] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/re... [resource schema] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/re...

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Hi Martin, =20 Thanks for looking into this! =20 1) Yes, Errai supports client-side request interceptors that can be = used to manipulate the request in any way you want (i.e. for caching or = security purposes): = http://docs.jboss.org/errai/3.0.3.Final/errai/reference/html_single/#sid-1= 9398997_ErraiJAX-RS-ClientsideInterceptors. However, the content-type =

=20 2) By default, Errai comes with its own marshalling system and = customized JSON format. It supports heterogenous collections, immutable = types, back references and much more which required adding additional =

--Apple-Mail=_12774FE9-5503-4BA2-8215-8D69C7B462D7 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Hi, Just a quick follow-up on 2.) As it happens, I just received a pull request for the first part of this = (allow to plug in a simple custom JAX-RS marshaller). Yay, open source! = ;)=20 You can track the progress here: https://issues.jboss.org/browse/ERRAI-796 This will allow you to rename fields using Jackson annotations.=20 Cheers, Christian On Nov 19, 2014, at 12:01 PM, Christian Sadilek <csadilek@redhat.com> = wrote: header should really be controlled (and is automatically set) based on = the @Consumes annotation. Of course you can override it, if required. framework-specific information to the payload (i.e. type information, = object ids, etc.). In Errai JAX-RS you can also use standard Jackson = based JSON which all JAX-RS implementations support. Errai does support = customer marshallers too ( = http://docs.jboss.org/errai/3.0.3.Final/errai/reference/html_single/#sid-5= 931328_Marshalling-CustomMarshallers) but this feature is not aligned = with our Jackson support. We can talk about this more but it looks like = I=92ll have to add a feature for you here if that=92s a blocking = requirement?

=20 Cheers, Christian =20 On Nov 19, 2014, at 10:58 AM, Martin Betak <mbetak@redhat.com> wrote: =20

...

Hi all, =20 I've been exploring the possibilities of utilizing Errai JAX-RS for = REST client in=20 our current GWT-based frontend. This would be a complement to = Vojtech's oVirt.js library which is very native to javascript and utilizes dynamic discovery of = resources and actions. =20 Errai JAX-RS would enable us to reuse our restapi definitions of = resource interfaces and entities=20 and generate proxies automatically thus eliminating the need for = extensive manual code generation. =20 [errai jax-rs] = https://docs.jboss.org/author/display/ERRAI/Errai+JAX-RS =20 Unfortunately in my quest I stumbled upon some issues I couldn't = exactly google or solve=20 and I would like to ask Mark or Christian, whether the below is = somehow possible with Errai: =20 1) Adding custom header to every request (some form of request = interceptors) You, see our api returns by default XML and we of course want to = consume JSON. Thus adding 'Content-Type: application/json' as well as other custom = authentication headers is necessary for our usage. =20 2) Using custom JSONProvider/ObjectMapper instead of the default = Jackson one.=20 In our JSONProvider [1] we use custom ObjectMapper [2] mainly to map = JAX-B annotations to json. Without this for example errai generates marshaller for the = VMs resource =20 public class VMs { @XmlElement(name =3D "vm") protected List<VM> vMs; } =20 that expects json field called "vMs" instead of the JAX-B = specification "vm" which is the actual format returned from the API. There may be other differencies such as = [3] so I think the best solution would be if we could tell errai to use specific JSONProvider for = generating the marshallers. =20 This are the issues that so far seem to be the most blocking ones, = others may arise along the way. =20 Thank you for any help provided. =20 Best regards, =20 Martin =20 [1] = https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/= restapi/interface/definition/src/main/java/org/ovirt/engine/api/json/JSONP= rovider.java [2] = https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/= restapi/interface/definition/src/main/java/org/ovirt/engine/api/json/Custo= mObjectMapper.java [3] = https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/= restapi/interface/definition/src/main/java/org/ovirt/engine/api/json/Custo= mBeanFactory.java [resource schema] = https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/= restapi/interface/definition/src/main/resources/api.xsd =20

--Apple-Mail=_12774FE9-5503-4BA2-8215-8D69C7B462D7 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 <html><head><meta http-equiv=3D"Content-Type" content=3D"text/html = charset=3Dwindows-1252"></head><body style=3D"word-wrap: break-word; = -webkit-nbsp-mode: space; -webkit-line-break: = after-white-space;">Hi,<div><br></div><div>Just a quick follow-up on = 2.)</div><div><br></div><div>As it happens, I just received a pull = request for the first part of this (allow to plug in a simple custom = JAX-RS marshaller). Yay, open source! = ;) </div><div><br></div><div>You can track the progress = here:</div><div><a = href=3D"https://issues.jboss.org/browse/ERRAI-796">https://issues.jboss.or= g/browse/ERRAI-796</a></div><div><br></div><div>This will allow you to = rename fields using Jackson = annotations. </div><div><br></div><div>Cheers,</div><div>Christian</d= iv><div><br><div><div>On Nov 19, 2014, at 12:01 PM, Christian Sadilek = <<a href=3D"mailto:csadilek@redhat.com">csadilek@redhat.com</a>> = wrote:</div><br class=3D"Apple-interchange-newline"><blockquote = type=3D"cite"><meta http-equiv=3D"Content-Type" content=3D"text/html = charset=3Dwindows-1252"><div style=3D"word-wrap: break-word; = -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Hi = Martin,<div><br></div><div>Thanks for looking into = this!<br><div><div><br></div><div>1) Yes, Errai supports client-side = request interceptors that can be used to manipulate the request in any = way you want (i.e. for caching or security purposes): <a = href=3D"http://docs.jboss.org/errai/3.0.3.Final/errai/reference/html_singl= e/#sid-19398997_ErraiJAX-RS-ClientsideInterceptors">http://docs.jboss.org/= errai/3.0.3.Final/errai/reference/html_single/#sid-19398997_ErraiJAX-RS-Cl= ientsideInterceptors</a>. However, the content-type header should really = be controlled (and is automatically set) based on the @Consumes = annotation. Of course you can override it, if = required.</div><div><br></div><div>2) By default, Errai comes with its = own marshalling system and customized JSON format. It supports = heterogenous collections, immutable types, back references and much more = which required adding additional framework-specific information to the = payload (i.e. type information, object ids, etc.). In Errai JAX-RS you = can also use standard Jackson based JSON which all JAX-RS = implementations support. Errai does support customer marshallers too = ( <a = href=3D"http://docs.jboss.org/errai/3.0.3.Final/errai/reference/html_singl= e/#sid-5931328_Marshalling-CustomMarshallers">http://docs.jboss.org/errai/= 3.0.3.Final/errai/reference/html_single/#sid-5931328_Marshalling-CustomMar= shallers</a>) but this feature is not aligned with our Jackson support. = We can talk about this more but it looks like I=92ll have to add a = feature for you here if that=92s a blocking = requirement?</div><div><br></div><div>Cheers,</div><div>Christian</div><di= v><br></div><div><div><div>On Nov 19, 2014, at 10:58 AM, Martin Betak = <<a href=3D"mailto:mbetak@redhat.com">mbetak@redhat.com</a>> = wrote:</div><br class=3D"Apple-interchange-newline"><blockquote = type=3D"cite">Hi all,<br><br>I've been exploring the possibilities of = utilizing Errai JAX-RS for REST client in <br>our current GWT-based = frontend. This would be a complement to Vojtech's oVirt.js = library<br>which is very native to javascript and utilizes dynamic = discovery of resources and actions.<br><br>Errai JAX-RS would enable us = to reuse our restapi definitions of resource interfaces and entities = <br>and generate proxies automatically thus eliminating the need for = extensive manual<br>code generation.<br><br>[errai jax-rs] <a = href=3D"https://docs.jboss.org/author/display/ERRAI/Errai+JAX-RS">https://= docs.jboss.org/author/display/ERRAI/Errai+JAX-RS</a><br><br>Unfortunately = in my quest I stumbled upon some issues I couldn't exactly google or = solve <br>and I would like to ask Mark or Christian, whether the below = is somehow possible with Errai:<br><br>1) Adding custom header to every = request (some form of request interceptors)<br>You, see our api returns = by default XML and we of course want to consume JSON.<br>Thus adding = 'Content-Type: application/json' as well as other custom authentication = headers<br>is necessary for our usage.<br><br>2) Using custom = JSONProvider/ObjectMapper instead of the default Jackson one. <br>In our = JSONProvider [1] we use custom ObjectMapper [2] mainly to map JAX-B = annotations<br>to json. Without this for example errai generates = marshaller for the VMs resource<br><br>public class VMs {<br> =    @XmlElement(name =3D "vm")<br> =    protected List<VM> vMs;<br>}<br><br>that expects = json field called "vMs" instead of the JAX-B specification "vm" which is = the actual<br>format returned from the API. There may be other = differencies such as [3] so I think the best solution<br>would be if we = could tell errai to use specific JSONProvider for generating the = marshallers.<br><br>This are the issues that so far seem to be the most = blocking ones, others may arise along the way.<br><br>Thank you for any = help provided.<br><br>Best regards,<br><br>Martin<br><br>[1] <a = href=3D"https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/= modules/restapi/interface/definition/src/main/java/org/ovirt/engine/api/js= on/JSONProvider.java">https://github.com/oVirt/ovirt-engine/blob/master/ba= ckend/manager/modules/restapi/interface/definition/src/main/java/org/ovirt= /engine/api/json/JSONProvider.java</a><br>[2] <a = href=3D"https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/= modules/restapi/interface/definition/src/main/java/org/ovirt/engine/api/js= on/CustomObjectMapper.java">https://github.com/oVirt/ovirt-engine/blob/mas= ter/backend/manager/modules/restapi/interface/definition/src/main/java/org= /ovirt/engine/api/json/CustomObjectMapper.java</a><br>[3] <a = href=3D"https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/= modules/restapi/interface/definition/src/main/java/org/ovirt/engine/api/js= on/CustomBeanFactory.java">https://github.com/oVirt/ovirt-engine/blob/mast= er/backend/manager/modules/restapi/interface/definition/src/main/java/org/= ovirt/engine/api/json/CustomBeanFactory.java</a><br>[resource schema] <a = href=3D"https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/= modules/restapi/interface/definition/src/main/resources/api.xsd">https://g= ithub.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/restapi/i= nterface/definition/src/main/resources/api.xsd</a><br></blockquote></div><= br></div></div></div></div></blockquote></div><br></div></body></html>= --Apple-Mail=_12774FE9-5503-4BA2-8215-8D69C7B462D7--