[ovirt-devel] Evaluating Errai JAX-RS for oVirt

[Christian Sadilek]

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! ;) 

You can track the progress here:
https://issues.jboss.org/browse/ERRAI-796

This will allow you to rename fields using Jackson annotations. 

Cheers,
Christian

On Nov 19, 2014, at 12:01 PM, Christian Sadilek <csadilek at redhat.com> wrote:

> Hi Martin,
> 
> Thanks for looking into this!
> 
> 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-19398997_ErraiJAX-RS-ClientsideInterceptors. 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.
> 
> 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 ( http://docs.jboss.org/errai/3.0.3.Final/errai/reference/html_single/#sid-5931328_Marshalling-CustomMarshallers) but this feature is not aligned with our Jackson support. We can talk about this more but it looks like I’ll have to add a feature for you here if that’s a blocking requirement?
> 
> Cheers,
> Christian
> 
> On Nov 19, 2014, at 10:58 AM, Martin Betak <mbetak at redhat.com> 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.
>> 
>> [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/restapi/interface/definition/src/main/java/org/ovirt/engine/api/json/JSONProvider.java
>> [2] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/restapi/interface/definition/src/main/java/org/ovirt/engine/api/json/CustomObjectMapper.java
>> [3] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/restapi/interface/definition/src/main/java/org/ovirt/engine/api/json/CustomBeanFactory.java
>> [resource schema] https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/restapi/interface/definition/src/main/resources/api.xsd
> 

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