spring-security: JdbcDaoImpl compatible schema using JPA

@Entity
@Table(name = "users")
public class User {

	@Id
	@Column(nullable = false, length = 50)
	private String username;

	@Column(nullable = false, length = 50)
	private String password;

	@Column(nullable = false)
	private boolean enabled = true;

	@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
	private List<Authority> authorities;

	....
}

public class AuthorityId implements Serializable {

	private static final long serialVersionUID = -4251643133848097809L;

	String user;

	String authority;

	@Override
	public int hashCode() {
		int hash = 23;
		hash = hash * this.user.hashCode();
		hash = hash * 31 + this.authority.hashCode();

		return hash;
	}

	@Override
	public boolean equals(Object obj) {
		AuthorityId x = (AuthorityId) obj;
    	return (x.user.equals(this.user)) && (x.authority.equals(this.authority)); 
    }
}

@Entity
@Table(name = "authorities")
@IdClass(AuthorityId.class)
public class Authority {

	@Id
	@ManyToOne(fetch = FetchType.EAGER, optional = false)
	@JoinColumn(name = "username", nullable = false)
	private User user;

	@Id
	@Column(nullable = false, length = 50)
	private String authority;

	...
}