Trouble with my first RESTful Web Services - web-services

Question

i'm developing my firts RestFul webServices in javaEE6.
This is my Entity Bean
#XmlRootElement
#Entity
public class MyEntity implements Serializable {
#Id
#GeneratedValue
private long idEntity;
private String name;
private String description;
#OneToMany(mappedBy = "entity" , fetch = FetchType.EAGER)
private List<EntityB> list;
//Get and set
}
#Entity
public class EntityB {
#Id
#GeneratedValue
private long idCategoria;
#ManyToOne
private MyEntity myEntity;
}
this is my webServices
#Path("myentity")
#Produces( {MediaType.APPLICATION_XML , MediaType.APPLICATION_JSON })
#Consumes( {MediaType.APPLICATION_XML , MediaType.APPLICATION_JSON })
#Stateless
public class MyEntityService {
#Inject
MyEntityDao entityDao;
#GET
#Path("{id}/")
public MyEntity findById(#PathParam("id") Long id){
return entityDao.findById(id);
}
}
Finally i configured Jersey
#ApplicationPath("ws")
public class ApplicationConfig extends Application {
}
Now , if i try a invoke my web services (localhost:8080/xxxx/ws/myentity) i get this error:
HTTP Status 500 - javax.xml.bind.MarshalException - with linked exception: [com.sun.istack.SAXException2: A cycle is detected in the object graph. This will cause infinitely deep XML

Answer 1

You have a cyclic Graph of objects, which is not allowed , as it would result in an "infinite" XML.
MyEntity Holds a reference to EntityB , which holds a reference that goes back to MyEntity.
The marshaller will try to marshall MyEntity > EntityB > MyEntity > EntityB and so on.
You can mark MyEntity in EntityB as #XmlTransient, to avoid this.
However, It might not be a good idea to try to use the same Classes of objects across all your project (From persistence layers to communication layers).