polymorphism and inheritance in hibernate and mysql

In a spring mvc app using hibernate over MySQL, I am encountering problems when I try to create polymorphic subclasses that inherit their id from a BaseEntity. You can see my intended use when you read my AccessLog class below, which has properties of type BaseEntity. The actor_entity and target_entity properties should each be fillable with a variety of different types of entities, such as User, OutsideSystem, Document, etc., each of which inherit from BaseEntity.

How do I set this up in code?

Here is my current java:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class BaseEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    protected Integer id;
    //other stuff
}

@Entity
@Table(name="users")
public class User extends BaseEntity{
    //other stuff
}

@Entity
@Table(name = "accesslogs")
public class AccessLog extends BaseEntity{

    @ManyToOne
    @JoinColumn(name = "actorentity_id")
    private BaseEntity actor_entity;

    @ManyToOne
    @JoinColumn(name = "targetentity_id")
    private BaseEntity target_entity;

    @Column(name="action_code")
    private String action;
}

Here is my current DDL:

CREATE TABLE IF NOT EXISTS baseentity(
  id int(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY
)engine=InnoDB;SHOW WARNINGS;

CREATE TABLE IF NOT EXISTS accesslogs(
  id int(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
  actorentity_id int(11) UNSIGNED NOT NULL,
  targetentity_id int(11) UNSIGNED NOT NULL,
  action_code varchar(100),
  access_date DATETIME
)engine=InnoDB;SHOW WARNINGS;

CREATE TABLE roles (
  id int(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
  role varchar(20) NOT NULL
) ENGINE=InnoDB;

CREATE TABLE users (
  id int(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
  login varchar(20) NOT NULL,
  password varchar(20) NOT NULL
) ENGINE=InnoDB;

CREATE TABLE user_roles (
  user_id int(11) UNSIGNED NOT NULL,
  role_id int(11) UNSIGNED NOT NULL,
  KEY user (user_id),
  KEY role (role_id)
) ENGINE=InnoDB;