I have two classes, Employee and Manager. Manager extends Employee, as it is a type of employee. Employee has an instance of Manager, which represents the idea of an employee having one manager. Conversely, manager has a set of Employees. There are two tables, EMPLOYEE and MANAGER:
table EMPLOYEE
long ID
varchar NAME
long MANAGERID
table MANAGER
long ID
long EMPLOYEEID //a join on this field enables inheritance
The classes look like this:
Employee.java (setters and getters omitted for brevity):
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "EMPLOYEE", schema = "TEST01")
public class Employee extends hata.util.Entity implements java.io.Serializable {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name = "ID", unique = true, nullable = false)
protected Long id;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "MANAGERID")
protected Manager manager;
@Column(name = "FIRSTNAME", nullable = false, length = 50)
protected String firstname;
Manager.java
@Entity
@PrimaryKeyJoinColumn(name="EMPLOYEEID")
@Table(name = "MANAGER", schema = "TEST01")
public class Manager extends Employee implements java.io.Serializable {
@OneToMany(fetch = FetchType.LAZY, mappedBy = "manager")
private Set<Employee> employees = new HashSet<Employee>(0);
I have filled the tables with a few employees, and all of those employees have the same manager, except for one employee - the one who is the manager. He himself has no manager. (If you're following me correctly, then it should be obvious that I have 1 row in the manager table, with and EMPLOYEEID referring back to a row in the EMPLOYEE table that has null as it's MANAGERID).
So, this setup looked correct to me, however when I tried to query all Employee objects with:
Query q = em.createQuery("select em from Employee em");
result = (List<Employee>) q.getResultList();
I get a nasty stack trace:
Caused by: org.hibernate.PropertyAccessException: could not set a field value by reflection setter of hata.staff.entity.Employee.manager at org.hibernate.property.DirectPropertyAccessor$DirectSetter.set(DirectPropertyAccessor.java:151) at org.hibernate.tuple.entity.AbstractEntityTuplizer.setPropertyValues(AbstractEntityTuplizer.java:586) at org.hibernate.tuple.entity.PojoEntityTuplizer.setPropertyValues(PojoEntityTuplizer.java:231) at org.hibernate.persister.entity.AbstractEntityPersister.setPropertyValues(AbstractEntityPersister.java:3824) at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:153) at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:898) at org.hibernate.loader.Loader.doQuery(Loader.java:773) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270) at org.hibernate.loader.Loader.doList(Loader.java:2294) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172) at org.hibernate.loader.Loader.list(Loader.java:2167) at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:448) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1258) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:236) ... 108 more Caused by: java.lang.IllegalArgumentException: Can not set hata.staff.entity.Manager field hata.staff.entity.Employee.manager to hata.staff.entity.Employee at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:164) at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:168) at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81) at java.lang.reflect.Field.set(Field.java:680) at org.hibernate.property.DirectPropertyAccessor$DirectSetter.set(DirectPropertyAccessor.java:139) ... 124 more
Did I code this wrong, or can hibernate simply not handle this scenario? I'd appreciate any assistance.
