principal_id    permission    target
12312313        PERM1         1000
12312313        PERM2         1000
12312313        PERM2         1002

@Entity
...
public class Principal {
    @Id
    private long principalId;

    ...

    private Map<String, List<Long>> permissionMap;

}

@Entity
...
public class Principal {

    @Id
    private long principalId;
    /** Other properties **/
    @OneToMany
    private Set<Permission> permissions;
....
}

@Entity
@IdClass(PermissionId.class)
public class Permission {
    @Id
    private String permission;
    @Id
    private Long target

    public static class PermissionId implements Serializable {
        private String permission;
        private Long target;
        /** setters/getters hashcode and equals goes here **/
    }
}

@Embeddable
public class Permission {
    private String permission;
    private int target;
}

@ElementCollection
@CollectionTable(name="foo", joinColumns = @JoinColumn(name = "principal_id"))
private Set<Permission> permissions;

@ElementCollection
@CollectionTable(name="foo", joinColumns = @JoinColumn(name = "principal_id"))
@MapKeyColumn(name="permission")
@Column(name="target")
private Map<String, Integer> permissions;