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Mapping a map collection containing superclasses in Hibernate

I am trying to map a map collection of String, SuperClass using XML mapping files. Here's what I have:
<map name="mapName" cascade="all-delete-orphan">
<key column="ID" />
<index column="KEY" type="string" />
<one-to-many class="SuperClass" />
</map>
The SuperClass has (currently one but probably going to need some more in the future) a subclass that I'm going to call SubClass. So I have a bunch of SubClass and SuperClass objects in the map and when Hibernate attempts to search for them after adding them I get a
org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1
I'm pretty sure Hibernate is looking for classes of type SuperType when the objects in the map actually have some SubTypes as well.
Here's the gist of how the mapping was done for the hierarchy in case you need a better representation of what I'm talking about:
<class name="SuperClass" table="SUPER_CLASS">
...properties...
(contains some <component> tags as well if it matters)
<union-subclass name="SubClass" table="SUBCLASS">
...more properties...
</union-subclass>
</class>

Migrating Hibernate 3 to 5: relation hibernate_sequence does not exist

I am migrating an application running with Hibernate 3 to Hibernate 5.
I have a strange error:
ERROR: relation hibernate_sequence does not exist
We are using *.hbm.xml mapping files and everything was working fine until I changed the Hibernate version. I mean we have a pretty straight forward mapping with ID column and DB sequence generator and still Hibernate wasn't able to pick the correct config.
<hibernate-mapping>
<class name="com.boyan.MyClass" table="my_class">
<id name="id" type="long">
<column name="id" />
<generator class="sequence">
<param name="sequence">my_class_seq</param>
</generator>
</id>
...
</class>
</hibernate-mapping>

I started digging in the Hibernate code and saw that SequenceGenerator is deprecated and the new versions use SequenceStyleGenerator. I was very confused when I noticed that in the new version the property telling which is the sequence name is changed from sequence to sequence_name. So finally when I changed:
<param name="sequence">my_class_seq</param>
to:
<param name="sequence_name">my_class_seq</param>
everything worked.

I bumped in to the same problem and I was using annotations. Solution was the accepted answer JPA GenerationType.AUTO not considering column with auto increment. If using annotations following should be used.
#GenericGenerator(name = "my_seq", strategy = "native", parameters = {
#Parameter(name = "sequence_name", value = "mydb_seq")
})

Hibernate unsaved-value annotation

I would like to force Hibernate (4.2) checking object persistence by the field VERSION instead of the field ID. The xml below should work:
<id name="id" column="ID">
<generator class="assigned" />
</id>
<version name="version" column="VERSION" unsaved-value="null" />
But I want to use annotations. Is this java code enough?
#Id
public String getId() {
return this.id;
}
#Version
public Integer getVersion() {
return this.version;
}
How to specify the unsaved-value tag? I don't find any annotation for this.
I've read somewhere, that Hibernate is smart enough to guess that an object is persistent or not, but it was not too convincing.
And what if I want to use -1 instead of null? There must be a way to achieve this, isn't it?
<version name="version" column="VERSION" unsaved-value="negative" />
Thanks for your help.
Edited. Hibernate 3.6 ref guide says:
"The unsaved-value attribute is almost never needed in Hibernate3 and indeed has no corresponding element in annotations."
and
"The assigned generator makes Hibernate use unsaved-value="undefined". This forces Hibernate to go to the database to determine if an instance is transient or detached, unless there is a version or timestamp property, or you define Interceptor.isUnsaved()."
I belive #Version will be sufficient for me.

Hibernate mapping with one-to-many polymorphic relationship

I have the following class diagram and I want to map it to a database (note that Person has a list with objects of class Vehicle).
Also my database looks like:
All tables in the database that represent a subclass of the Vehicle class have all the fields of the superclass Vehicle. Also, all the relations show a one-to-many relationship from Person to Vehicle, Car and Motorcycle.
My hibernate mapping files are the following:
Person.hbm.xml
<hibernate-mapping package="....">
<class name="Person" table="Persons">
<id name="key" column="Person_ID">
<generator class="native"/>
</id>
<list name="ownedVehicles" inverse="false" cascade="all">
<key column="Person_ID" not-null="true" />
<list-index column="idx"/>
<one-to-many class="Vehicle"/>
</list>
</class>
</hibernate-mapping>
Vehicle.hbm.xml
<hibernate-mapping package="...">
<class name="Vehicle" table="Vehicles" polymorphism="implicit">
<id name="id" type="int" column="Vehicle_ID">
<generator class="increment"/>
</id>
<property name="numOfSeats"/>
<union-subclass name="Car" table="Cars"></union-subclass>
<union-subclass name="Motorcycle" table="Motorcycles"></union-subclass>
</class>
</hibernate-mapping>
The problem (error I get) is the following:
Hibernate: insert into Persons (Person_ID) values (default)
2013-06-26 15:41:52 WARN JdbcCoordinatorImpl:424 - HHH000386: ResultSet had no statement associated with it, but was not yet registered
Hibernate: update Car set numOfSeats=? where Vehicle_ID=?
org.hibernate.StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1
I get this error when I run:
Car car = new Car();
car.setNumOfSeats(5);
Person person = new Person();
person.getOwnedVehicles().add(car);
ManagePerson managePerson = new ManagePerson();
Integer personID = managePerson.store(person);
The store() function of ManagePerson actually creates a session and a transaction and then uses the save() method provided by Hibernate to persist the objects into the database.
As far as I understand Hibernate usually will do insert into Persons, then insert into Cars and finally update Cars (the update is done to save the foreign keys on Cars table that will reference the Person that owns the cars). However, here this is not the case and the insert into Cars seems to be getting skipped. I understood how Hibernate works here by trying person.getOwnedVehicles().add(vehicle); instead of person.getOwnedVehicles().add(car); on the code given above.
As you might understand, I am trying to see if Hibernate actually understands in which "subclass" table a record should go, depending on the class of the object contained in the ownedVehicle list of the Person class. For example, if the ownedVehicles has an object of class Car and one of class Motorcycle, then each of these should go to Cars and Motorcycle tables respectively.
Note: I am using Hibernate 4.2.2 and HSQLDB 2.2.9.
I would appreciate any help with this.
Thanks.

I think it is just a matter of incorrect use of the implicit polymorphism of Hibernate.
Implicit polymorphism for your case can only work by changing your list to have
inverse="true". This can be done of course if your Vehicle class also 'knows' about the relationship with the Person class (e.g. by adding an 'Owner' property and the corresponding mapping).
(Have a look at this table and the case of "table per concrete-class (union-subclass)" and one-to-many associations.
If you enable logging and raise the log level to DEBUG you would see that currently Hibernate tries to update the Vehicles table with the Person_ID instead of the Car table like you meant it to. This is because of the inverse="true" and the limitations of the combination of the Table-per-concrete-class mapping strategy and implicit polymorphism (have a look at the documentation).
So, by having the Vehicle class know about its Owner and using inverse="true" you should be able to succeed in what you are trying to do. Either this or try one of the other inheritance mapping strategies (again have a look at the documentation).

If the managePerson.store(...) method doesn't have a recursive call to the objects in "getOwnedVehicles()" such that it can then call their "store" methods then you shouldn't expect that the created "car" object would be inserted into the table.
You are in fact calling "managePerson.store" not "manageCar.store", I'd have to see the code in the .store(...) method to be sure though but I would expect that it is not doing an iteration of the Vehicles and is not doing an insert for any discovered ones (why should it unless you built it explicitly to do that?).

how to define an inverse cascade delete on a many-to-one mapping in hibernate

I have two classes A and B. Many B's can have association with a single A, hence a many-to-one relationship from B to A. I've mapped the relationship like:
<class name="A" table="tbl_A">
<property name="propA" column="colA"/>
</class>
<class name="B" table="tbl_B">
<property name="propB" column="colB"/>
<many-to-one name="a" class="A" column="col1" cascade="delete"/>
</class>
A has nothing mapped to B. Keeping this in mind we intend to delete B when it's associated A is deleted. This could have been possible if I could define an inverse="true" on the many-to-one association in B but hibernate does not allow that.
Can anyone help with this? We do not want to write anything in A for this.

Hibernate only cascades along the defined associations. If A knows nothing about Bs, nothing you do with A will affect Bs.
Pascal's suggestion is, therefore, the easiest way to do what you want:
<class name="A" table="tbl_A">
...
<set name="myBs" inverse="true" cascade="all,delete-orphan">
<key column="col1"/>
<one-to-many class="B"/>
</set>
</class>
<class name="B" table="tbl_B">
...
<many-to-one name="a" class="A" column="col1" not-null="true"/>
</class>
Note that setting cascade="delete" on B as you have it in your original code will NOT do what you want - it tells Hibernate to "delete A if B is deleted" which is likely to result in constraint violation (if there are any other Bs linked to that A).
If you absolutely cannot add a collection of Bs to A (though I can't really think of the circumstances where that'd be the case), your only other alternative is to define cascade delete from A to B at the foreign key level; your Bs will then be deleted when your A is deleted.
This is a rather ugly solution, however, because you have to be extremely careful of how you delete A in Hibernate:
Session must be flushed prior to deleting A (having pending updates to B may result in an error or A and some Bs being re-inserted behind the scenes)
All Bs linked to your A (and since you're not maintaining the relationship from A side that means all Bs) must be evicted from all active sessions and 2nd level cache.

I think you need to cascade="all,delete-orphan" from A to B's with a one-to-many association.