Spring 3.1 Hibernate 4 exception for Inheritance [cannot be cast to org.hibernate.mapping.RootClass]

It is due to Id column in both classes. Remove the Id from HumanMicroTask.

to fix this Remove @Id from Subclass

in MicroTask keep

   @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    @Column(name = "MICROTASKID")
    private String microTaskId;

in Subclass HumanMicroTask remove

   @Id
    @Column(name = "HMTID")
    private String humanMicroTaskid;

I had the same problem some time ago, since your parent class has a primary key: 'Id', when the subclasses are generated they automatically generate a foreign key with the exact name of their parent's primary key

Example: (Pseudocode)

Entity Definition

Parent Class

  @Entity
    @Inheritance(strategy = InheritanceType.JOINED)
    @Table(name = "abstract_person", catalog = "catalog", schema = "")
    class AbstractPerson{

        //Primary Key
        @Id
        @Column(name = "idPerson")
        int idPerson;

        @Basic
        @Column(name = "name")
        String name;

        //corresponding getters and setters
    }

Child Class:

 @Entity
    @Table(name = "concrete_person", catalog = "catalog", schema = "")
    class ConcretePerson extends AbstractPerson{

       //No id or primary key is defined here

        @Basic
        @Column(name="profession")
        String profession;

    }

Table Generation

Parent class will map to this

Table "abstract_person"
id: Int (primary key)
name: Varchar

Child class will map to this:

Table "concrete_person"
profession: Varchar
idPerson: int (Automatically generated, foreign key to parent table and primary class of this table)

//Assumptions
Mysql database;
Jpa 2 Hibernate Implementation;
NetBeans 7x Ide