RequestFactory: Proxy implementing interface with generics

问题

I am struggling with requestfactories and generics. In the code below, the proxy methods are matching exactly with the entity methods, but I get the log trace:

java.lang.NullPointerException: null
    at com.google.web.bindery.autobean.vm.impl.MethodPropertyContext.traverse(MethodPropertyContext.java:102) ~[gwt-servlet-2.6.0.jar:na]
    at com.google.web.bindery.autobean.vm.impl.MethodPropertyContext.accept(MethodPropertyContext.java:75) ~[gwt-servlet-2.6.0.jar:na]
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$PropertyCoderCreator.maybeCreateCoder(AutoBeanCodexImpl.java:353) ~[gwt-servlet-2.6.0.jar:na]
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$PropertyCoderCreator.visitReferenceProperty(AutoBeanCodexImpl.java:341) ~[gwt-servlet-2.6.0.jar:na]
    at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:324) ~[gwt-servlet-2.6.0.jar:na]
    at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166) ~[gwt-servlet-2.6.0.jar:na]
...

My proxy class:

@ProxyFor(value = OutilLibre.class, locator = OutilLibreLocator.class)
public interface OutilLibreProxy extends ProxyWithId, ProxyWithCartoLibre<OutilProxy>, EntityProxy {

    public Long getId();

    public void setId(Long id);

    @Override
    OutilProxy getCompetence();

    @Override
    void setCompetence(OutilProxy outil);

    @Override
    String getCompetenceAutre();

    @Override
    void setCompetenceAutre(String competence);

}

The interface with generics:

public interface ProxyWithCartoLibre<T> {

    T getCompetence();

    void setCompetence(T competence);

    String getCompetenceAutre();

    void setCompetenceAutre(String competence);

}

The corresponding server entity:

@Entity
@Table(name = "outil_libre")
public class OutilLibre extends AEntityLongId implements IBeanCartoLibre<Outil>, IUniqueVersionEntity {

    private static final long serialVersionUID = 45107725880220830L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "outil_libre_seq_gen")
    @SequenceGenerator(name = "outil_libre_seq_gen", sequenceName = "seq_outil_libre")
    @Column(name = "id", unique = true, nullable = false, precision = 5, scale = 0)
    private Long id;

    @Cascade(value = {org.hibernate.annotations.CascadeType.SAVE_UPDATE})
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "outil", nullable = false)
    private Outil outil;

    @Column(name = "outil_autre")
    private String outilAutre;

    @Override
    public Long getId() {
        return id;
    }

    @Override
    public void setId(Long id) {
        this.id = id;
    }

    @Override
    public Outil getCompetence() {
        return outil;
    }

    @Override
    public void setCompetence(Outil outil) {
        this.outil = outil;
    }

    @Override
    public String getCompetenceAutre() {
        return outilAutre;
    }

    @Override
    public void setCompetenceAutre(String competence) {
        this.outilAutre = competence;
    }

}

I don't know why I get this error because the ProxyWithCartoLibre interface is just used by client side classes and hasn't any purpose in defining the requestfactory.

Is there a way to tell the GWT generator to exclude the ProxyWithCartoLibre interface?

Thanks in advance.

EDIT

java.lang.NullPointerException: null
     at com.google.web.bindery.autobean.vm.impl.MethodPropertyContext.traverse(MethodPropertyContext.java:102) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.vm.impl.MethodPropertyContext.accept(MethodPropertyContext.java:75) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$PropertyCoderCreator.maybeCreateCoder(AutoBeanCodexImpl.java:353) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$PropertyCoderCreator.visitReferenceProperty(AutoBeanCodexImpl.java:341) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:324) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl.doCoderFor(AutoBeanCodexImpl.java:522) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.setProperty(AbstractAutoBean.java:276) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.setProperty(ProxyAutoBean.java:253) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.vm.impl.BeanPropertyContext.set(BeanPropertyContext.java:44) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.requestfactory.server.Resolver$PropertyResolver.visitValueProperty(Resolver.java:211) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:289) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.requestfactory.server.Resolver.resolveClientValue(Resolver.java:470) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.processInvocationMessages(SimpleRequestProcessor.java:491) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:233) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:135) ~[gwt-servlet.jar:na]
     at com.google.web.bindery.requestfactory.server.RequestFactoryServlet.doPost(RequestFactoryServlet.java:133) ~[gwt-servlet.jar:na]
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) [servlet-api.jar:na]
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) [servlet-api.jar:na]
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39.B]
     at ch.qos.logback.access.servlet.TeeFilter.doFilter(TeeFilter.java:55) [logback-access-1.0.13.jar:na]
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39.B]
     at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:180) [spring-orm-3.2.4.RELEASE.jar:3.2.4.RELEASE]
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-3.2.2.RELEASE.jar:3.2.2.RELEASE]
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39.B]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:146) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:183) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:183) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160) [spring-security-web-3.1.4.RELEASE.jar:3.1.4.RELEASE]
     at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346) [spring-web-3.2.2.RELEASE.jar:3.2.2.RELEASE]
     at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259) [spring-web-3.2.2.RELEASE.jar:3.2.2.RELEASE]
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39.B]
     at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) [spring-web-3.2.2.RELEASE.jar:3.2.2.RELEASE]
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-3.2.2.RELEASE.jar:3.2.2.RELEASE]
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) [catalina.jar:7.0.39.B]
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) [catalina.jar:7.0.39.B]
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) [catalina.jar:7.0.39.B]
     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947) [catalina.jar:7.0.39.B]
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) [catalina.jar:7.0.39.B]
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) [catalina.jar:7.0.39.B]
     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009) [tomcat-coyote.jar:7.0.39.B]
     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) [tomcat-coyote.jar:7.0.39.B]
     at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) [tomcat-coyote.jar:7.0.39.B]
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_60]
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_60]
     at java.lang.Thread.run(Thread.java:745) [na:1.7.0_60]

回答1:

I also got this exception and tried a lot and came up with the following workaround:

build a basic "underlying" bean/POJO model for your classes avoiding generics (in the outmost class, using generics does not seem to be a problem) and maybe using some "marker strings" like _ to help avoiding (via "optimistic" interface usage) later usage of "undesired classes/methods" or provide desired variants, e.g.:

interface _Person< PERSON extends _Person<PERSON> > extends IsSerializable {  
                   // generics here: just to show that generics work if _Person is not 
                   // referenced itself in AutoBean (de)serialization
  int getId();
  void setId( int id );     // normally we may not want to expose this, but for the
                            // (de)serialization it is/may be necessary or benefitial 
                            // here now
  String getName();
  void setName( String name );
  //_Person setName_( String name );
                        // to have fluent setters is against Bean definition and does 
                        // not work with AutoBeans, but since there is no getter
                        // "getName()" it is ignored and would work :-)
                        // (but it may be better to not include it in here)
  _Address getAddr_();
  void setAddr_( _Address addr );
}

//interface _Address< ADDR extends _Address > extends IsSerializable {
  // => would e.g. cause the NullPointerException ! :-(
  //    at com.google.web.bindery.autobean.vm.impl.MethodPropertyContext.traverse(
  //         MethodPropertyContext.java:102) ~[gwt-user-2.6.0.jar:na]
interface _Address extends IsSerializable {
   String getCity_();
   void setCity_( String city );
}

now using this with AutoBean functionality will work on those and if one uses generic interfaces and implementations around these later on should work (I tried only a simple example like this to test it for me). Example with above should work (incomplete snippet): AutoBeanCodex.encode( personAutoBean ).deepCopy()

now creating generic interfaces and classes inheriting from those would have the disadvantage of e.g. not beeing able to

return a generic person.getAddr_().getNonBeanFooExtension() or
utilize a fluent interface like person.setName_( "foo" ).setMail( "bar" ) or
preventing/discourage access to person.setId( 123 )

Therefore I am planning now (I'll report back when it's done) to derive from these beens nevertheless, but also writing "inheritance unrelated"/overlapping interfaces, that are/should be "normally" used throughout the business application, e.g.:

interface Person< PERSON extends Person<PERSON>> {
   // extends _Person <= no, because then we could not "hide/discourage" users calling 
   // e.g. "setId(....)"
  int getId();

  String getName();
  //void setName( String name );  // we could provide it, but setName_() does the same
                                  // and more and only one setter keeps the interface 
                                  // smaller
  PERSON setName_( String name );
  Address<PERSON> getAddr();
  PERSON setAddr( Address<PERSON> addr );

  PERSON setFancyThing();          // not "seen" by AutoBean and thus should not 
                                   // cause trouble there
}

interface Address< PERSON extends Person<PERSON> > {
  ...
}

now implementing classes like this should work in general (only tested simple case for now):
```
class PersonDTO implements Person<PersonDTO>, _Person<PersonDTO> {
  ...
}
```
the "users" of those implementations should as much as possible work with the interfaces from 2. Person<PersonDto> pers = ... so they see some quite nice person interface and can't easily call pers.setId( 123 ), but pers.setName_( "Dimitri Khalezov" ).setMail_( ... )

It's already a long post and I hope you can imagine the missing details in various locations.

来源：https://stackoverflow.com/questions/24672800/requestfactory-proxy-implementing-interface-with-generics

标签

java

generics

gwt

requestfactory