Help! How to use model objects with generics

[brt...@gmail.com]

I have inherited a database model where the primary keys are sometimes integers and sometimes strings. To simplify our domain object model, I've used a class generic to abstract away whether the "id" property of the class is a number or a string. This code works great and I've used it before in past projects.

Vraptor doesn't seem to like either the inheritance or the generic typing (I'm guessing it's the generics). If I remove the extends on the Brand class and put id, created, modified, and status right into the class, Vraptor works as advertised. If I try to use the Brand class as shown below I get the exception sun.reflect.generics.reflectiveObjects.TypeVariableImpl cannot be cast to java.lang.Class.

What are my options?

The model looks like this

public class Brand extends AbstractPersistedObject<Integer> {

private static final long serialVersionUID = 1L;

private String name;

public Brand() {

super();

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

import java.io.Serializable;

import java.util.Date;

public interface Persisted<T> extends Serializable {

public boolean isPersisted();

public boolean equalsPrimaryKey(Persisted other);

public T getId();

public void setId(T id);

public Date getCreated();

public void setCreated(Date created);

public String getCreatedBy();

public void setCreatedBy(String createdBy);

public Date getModified();

public void setModified(Date modified);

public String getModifiedBy();

public void setModifiedBy(String modifiedBy);

public Status getStatus();

public void setStatus(Status status);

}

import java.lang.reflect.ParameterizedType;

import java.util.Date;

public abstract class AbstractPersistedObject<T> implements Persisted<T> {

/**

     * Unique identifier for this object in the database. May be a String or an Integer.

*/

protected T id;

private final Class<T> type;

protected Date created;

protected String createdBy;

protected Date modified;

protected String modifiedBy;

protected Status status = Status.A;

public AbstractPersistedObject() {

this.type = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];

}

@Override

public T getId() {

return id;

}
@Override

public void setId(T id) {

this.id = id;

}

@Override

public Date getCreated() {

return created;

}

@Override

public void setCreated(Date created) {

this.created = created;

}

@Override

public String getCreatedBy() {

return createdBy;

}

@Override

public void setCreatedBy(String createdBy) {

this.createdBy = createdBy;

}

@Override

public Date getModified() {

return modified;

}

@Override

public void setModified(Date modified) {

this.modified = modified;

}

@Override

public String getModifiedBy() {

return modifiedBy;

}

@Override

public void setModifiedBy(String modifiedBy) {

this.modifiedBy = modifiedBy;

}

@Override

public Status getStatus() {

return status;

}

@Override

public void setStatus(Status status) {

this.status = status;

}

}

The controller looks like this

List<Brand> brands = new ArrayList<>();

try {

brands = brandDao.getAllBrands();

} catch (Exception e) {

log.error(ExceptionUtils.getStackTrace(e));

}

result.include("brands", brands);

}

@Path("/admin/brand/{id}")

public void editBrand(Integer id) {

Brand brand = null;

try {

brand = brandDao.getBrandById(id);

} catch (Exception e) {

log.error(ExceptionUtils.getStackTrace(e));

}

result.include("brand", brand);

}

@Path("/admin/brand/save")

@IncludeParameters

public void saveBrand(Brand brand) {

log.debug("Saving Brand " + brand.getName());

try {

brandDao.saveBrand(brand);

} catch (Exception e) {

log.error(ExceptionUtils.getStackTrace(e));

}

result.redirectTo(this).brands();

}

The view looks like this

<form role="form" method="post" action="${linkTo[AdminController].saveBrand}">

<input type="hidden" name="brand.id" value="${brand.id}"/>

<input type="text" name="brand.name" value="${brand.name}"/>

<input type="radio" name="brand.status" value="A"/>Active

<input type="radio" name="brand.status" value="D"/>Disabled

<button type="submit" class="btn btn-default">Submit</button>

</form>

An exception occurred: java.lang.Throwable: br.com.caelum.vraptor.http.InvalidParameterException: Exception when trying to instantiate Target(name=brand, type=class com.a.domain.Brand)

Caused by: br.com.caelum.vraptor.http.InvalidParameterException: Exception when trying to instantiate Target(name=brand, type=class com.a.domain.Brand)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator.handleException(VRaptorInstantiator.java:124)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator.instantiate(VRaptorInstantiator.java:118)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator.instantiate(VRaptorInstantiator.java:110)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator$Proxy$_$$_WeldClientProxy.instantiate(Unknown Source)

at br.com.caelum.vraptor.http.iogi.IogiParametersProvider.instantiateOrAddError(IogiParametersProvider.java:87)

at br.com.caelum.vraptor.http.iogi.IogiParametersProvider.instantiateParameters(IogiParametersProvider.java:80)

at br.com.caelum.vraptor.http.iogi.IogiParametersProvider.getParametersFor(IogiParametersProvider.java:72)

at br.com.caelum.vraptor.http.iogi.IogiParametersProvider$Proxy$_$$_WeldClientProxy.getParametersFor(Unknown Source)

at br.com.caelum.vraptor.observer.ParametersInstantiator.getParametersForCurrentMethod(ParametersInstantiator.java:149)

at br.com.caelum.vraptor.observer.ParametersInstantiator.instantiate(ParametersInstantiator.java:89)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:606)

at org.jboss.weld.injection.StaticMethodInjectionPoint.invoke(StaticMethodInjectionPoint.java:88)

at [internal classes]

at br.com.caelum.vraptor.core.DefaultInterceptorStack.start(DefaultInterceptorStack.java:90)

at br.com.caelum.vraptor.core.DefaultInterceptorStack$Proxy$_$$_WeldClientProxy.start(Unknown Source)

at br.com.caelum.vraptor.observer.RequestHandlerObserver.handle(RequestHandlerObserver.java:93)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:606)

at org.jboss.weld.injection.StaticMethodInjectionPoint.invoke(StaticMethodInjectionPoint.java:88)

at [internal classes]

at br.com.caelum.vraptor.VRaptor.doFilter(VRaptor.java:123)

at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:207)

... 1 more

Caused by: java.lang.ClassCastException: sun.reflect.generics.reflectiveObjects.TypeVariableImpl cannot be cast to java.lang.Class

at br.com.caelum.iogi.reflection.Target.findRawClassType(Target.java:37)

at br.com.caelum.iogi.reflection.Target.getClassType(Target.java:29)

at br.com.caelum.iogi.reflection.Target.toString(Target.java:108)

at java.lang.String.valueOf(String.java:2849)

at java.lang.StringBuilder.append(StringBuilder.java:128)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator.handleException(VRaptorInstantiator.java:124)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator.instantiate(VRaptorInstantiator.java:118)

at br.com.caelum.iogi.reflection.NewObject.setProperty(NewObject.java:58)

at br.com.caelum.iogi.reflection.NewObject.populateProperties(NewObject.java:52)

at br.com.caelum.iogi.reflection.NewObject.valueWithPropertiesSet(NewObject.java:42)

at br.com.caelum.iogi.ObjectInstantiator.instantiate(ObjectInstantiator.java:30)

at br.com.caelum.iogi.MultiInstantiator.instantiate(MultiInstantiator.java:20)

at br.com.caelum.vraptor.http.iogi.VRaptorInstantiator.instantiate(VRaptorInstantiator.java:116)

... 26 more

[brt...@gmail.com]

Just confirmed that even if I add a simple Converter for the Brand object I still get the same exception

@Convert(Brand.class)

@ApplicationScoped

public class BrandConverter implements Converter<Brand> {

@Inject

private BrandDao brandDao;

@Override

public Brand convert(String value, Class<? extends Brand> type) {

Brand brand = new Brand();

if (StringUtils.isNumeric(value)) {

try {

brand = brandDao.getBrandById(Integer.valueOf(value));

} catch (Exception e) {

log.error(ExceptionUtils.getStackTrace(e));

}

}

return brand;

}

}

[Lucas Cavalcanti]

Hi, after adding the converter try to change the input hidden to:

<input type="hidden" name="brand" value="${brand.id}"/>

this way the converter will be called, and VRaptor (with IOGI) won't try to call setId()

Other way to fix this is to open an issuer (or a Pull Request) on IOGI mentioning this:

https://github.com/rafaeldff/Iogi

[]'s

Lucas Cavalcanti

livro de VRaptor: www.casadocodigo.com.br/products/livro-vraptor

github.com/lucascs

@lucascs

--
You received this message because you are subscribed to the Google Groups "caelum-vraptor-en" group.
To unsubscribe from this group and stop receiving emails from it, send an email to caelum-vraptor...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[brt...@gmail.com]

Lucas, you're a life saver! Thank you. It would be a cool feature request for the IOGI project to see if we couldn't figure out a way to make it work.

Curious if there is a flow chart anywhere of the Vraptor request/response lifecycle? I'm thinking something along the lines of this diagram which is part of this guy's blog on Spring Web MVC http://www.cnblogs.com/fangwenyu/archive/2012/10/11/2716665.html

[Lucas Cavalcanti]

We have this diagram:

https://raw.githubusercontent.com/caelum/vraptor4/master/vraptor-site/content/img/vraptorEventPipeline.png

VRaptor's lifecycle is event-based, with some observers affecting the response.

[]'s

Lucas Cavalcanti

livro de VRaptor: www.casadocodigo.com.br/products/livro-vraptor

github.com/lucascs

@lucascs