I'd recommend using DTO's. Whether you use Dozer or not is secondary.
The motivations for this approach are in this thread -
http://groups.google.com/group/google-web-toolkit/msg/f9290388bbf5a5f8. In
general, you want to keep your UI Model (i.e. DTO) separate from your Domain
Model (hibernate entities). And Performance is not the only reason for this
- there are going to be times when you don't want to some information to the
client due to security/privacy concerns.
--Sri
On 20 May 2010 16:27, Frederic Conrotte <frederic.conro...@gmail.com> wrote:
> Hello
>
> On our current project we have a fairly large database model mapped
> thru Hibernate JPA annotations: around 150 entities.
> Those JPA entities have a lot of @ManyToOne, @OneToMany, @ManyToMany
> inter relations.
>
> On the server side Hibernate lazy loading is active and managed
> correctly so that no extra unneeded collections are fetched to the
> client.
>
> I’m using Gilead in stateless mode with all JPA entities extending
> java.io.Serializable and net.sf.gilead.pojo.gwt.LightEntity
>
> So back to the client side, I created a simple RPC Service
>
> @RemoteServiceRelativePath("country.rpc")
> public interface CountryService extends RemoteService
> {
> Country findCountry(String countryId);
> }
>
> public interface CountryServiceAsync
> {
> void findCountry(String countryId, AsyncCallback<Country>
> callback);
> }
>
> The Country type has several Collection fields whose type have as well
> their own relations. But, again, thanks to lazy loading, those
> collections are empty.
>
> Problem arise when I try to create the service using Development Mode
> (Run As Web Application in Eclipse)
>
> CountryServiceAsync countryService = GWT.create(CountryService.class);
>
> GWT.create()'s goal is to create a client proxy for the remote
> service's server side implementation.
>
> Extract from the "Development Mode" console:
>
> 12:30:18.664 [DEBUG] [project] Invoking
> com.google.gwt.dev.javac.standardgeneratorcont...@904576
> 12:30:18.664 [DEBUG] [project] Generating client proxy for remote
> service interface
> 'com.company.project.client.services.CountryServiceClient'
> 12:30:18.664 [DEBUG] [project] Analyzing
> 'com.company.project.client.services.CountryServiceClient' for
> serializable types
> 12:30:18.664 [DEBUG] [project] Analyzing methods:
> 12:30:18.664 [DEBUG] [project] public abstract
> com.company.project.server.dom.Country findCountry(java.lang.String
> countryId)
> 12:30:18.664 [DEBUG] [project] Return type:
> com.company.project.server.dom.Country
> 12:30:20.648 [DEBUG] [project] com.company.project.server.dom.Country
> 12:30:20.648 [DEBUG] [project] Finding possibly instantiable subtypes
> .
> .
> .
>
> Then a huge tree a dependent subtypes that qualify for serialization
> is built.
>
> At this point, GWT.create method returns after around 5 minutes !
>
> Nothing mentions in the documentation that Serialization performance
> depends on the number of imports of a types, including imported types
> of its children:
>
> http://code.google.com/webtoolkit/doc/latest/DevGuideServerCommunication.html#DevGuideMakingACall
>
> If you read this link:
>
> http://sinnema313.wordpress.com/2008/11/16/performance-tuning-a-gwt-application/
>
> It mentions that "Serialization is slow: (...) Serialization
> performance appears to be proportional to the number of objects, not
> just to their total size."
>
> I see 2 possible solutions:
> - Cache serializable types (gwt.rpc file) and load them with the
> module, but I don’t know if it's feasible with current GWT API
> - Use DTOs and Dozer to drastically denormalize our model object and
> limit the number of inter relations between types.
>
> Did any of you already faced this performance problem ?
>
> Thanks
>
> Fred
>
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